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 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN 
 
 L161 O-1096 
 
SWEET- CORN 
 
 INBREDS and 
 
 CROSSES 
 
 Released by the Illinois Station 
 
 By W. A. HUELSEN 
 
 UNIVERSITY OF ILLINOIS 
 AGRICULTURAL EXPERIMENT STATION 
 
 Bulletin 466 
 
CONTENTS 
 
 PAGE 
 
 DEVELOPMENT OF INTEREST IN HYBRIDS 279 
 
 ADVANTAGES OF SINGLE CROSSES 281 
 
 NATURE OF INCREASED YIELDS OF SWEET-CORN CROSSES... 283 
 REGIONAL ADAPTABILITY OF CROSSES 284 
 
 BREEDING METHODS USED 288 
 
 Selection Within Inbred Lines 288 
 
 Selfing of Desirable Crosses 292 
 
 Back-Crossing 292 
 
 Possible Deterioration in Inbred Lines 292 
 
 WHAT CONSTITUTES A GOOD INBRED LINE . 293 
 
 TWELVE INBRED LINES RELEASED 293 
 
 Results of Yield Tests with Single Crosses 295 
 
 Classification of Crosses 302 
 
 Selectivity of Inbreds in Relation to the Breeding Program 308 
 
 EVALUATING ILLINOIS COUNTRY GENTLEMAN INBREDS 309 
 
 Evaluation on Basis of Yields 309 
 
 Evaluation on Basis of Quality 315 
 
 Evaluation on Basis of Maturity 319 
 
 Evaluation on Basis of Individual Ear Weights 320 
 
 Evaluation on Basis of Smut Frequency 321 
 
 General Evaluation of Inbred Lines 321 
 
 NARROW GRAIN EVERGREEN INBREDS AND CROSSES 322 
 
 DESCRIPTION OF INBRED LINES 326 
 
 Illinois Country Gentleman Inbred 1 326 
 
 Illinois Country Gentleman Inbred 3 329 
 
 Illinois Country Gentleman Inbred 5 332 
 
 Illinois Country Gentleman Inbred 6 334 
 
 Illinois Country Gentleman Inbred 8 337 
 
 Illinois Country Gentleman Inbred 9 339 
 
 Illinois Country Gentleman Inbred 10 339 
 
 Illinois Country Gentleman Inbred 15 342 
 
 Illinois Narrow Grain Evergreen Inbred 11 343 
 
 Illinois Narrow Grain Evergreen Inbred 13 345 
 
 Illinois Narrow Grain Evergreen Inbred 14 347 
 
 Illinois Narrow Grain Evergreen Inbred 55 348 
 
 SUMMARY AND CONCLUSIONS 352 
 
 LITERATURE CITED. . . 355 
 
 Urbana, Illinois May, 1940 
 
 Publications in the Bulletin series report the results of investigations made 
 or sponsored by the Experiment Station 
 
Sweet -Corn Inbreds and Crosses 
 
 Released by the Illinois Station 
 
 By W. A. HUELSEN, Chief in Olericulture 
 DEVELOPMENT OF INTEREST IN HYBRIDS 
 
 YIELDS of corn can be increased by crossing two con- 
 tinuously inbred lines has been known since East 5 * and Shull 14 * 
 -"* demonstrated the effect of hybrid vigor in 1907 and 1908. At 
 that time, however, the methods used in inbreeding and crossing 
 promised nothing of commercial value; selection seemed more promis- 
 ing, in view of the results obtained by Hopkins 7 * and L. H. Smith. 16 * 
 Consequently, for many years breeders continued to select rather than 
 to inbreed. In 1918, however, following Jones's 10 * discussion of 
 heterosis, interest in single and double crosses revived. Since then 
 almost all corn breeders have depended entirely on inbreeding and 
 crossing to obtain better strains of corn. 
 
 In spite of the slight attention paid to sweet-corn breeding as com- 
 pared with field-corn breeding, the first large-scale commercial plant- 
 ings of crosses were made with sweet corn. The circumstances which 
 brought this about are an excellent illustration of how advances in one 
 field of research (breeding) are dependent on those in another 
 (engineering). 
 
 In the early days of canning, sweet corn was husked by hand and 
 the kernels cut from the cobs with butcher knives. The canned product 
 was known as "whole grain," or "Maryland" style corn. The first 
 cutting machine was introduced in 1882. This and subsequent machines 
 cut the tops from the kernels and then scraped out the remaining 
 kernel contents, giving a canned product known as "Maine" or "cream" 
 style corn. The older whole-grain type, because of the higher cost of 
 hand methods, practically disappeared from the market. 
 
 In 1929 a whole-grain cutter was introduced. This machine cut the 
 kernels down to the cob irrespective of the shape and size of the ear. 
 The cost of packing whole-grain style was thus reduced and packers 
 turned their attention to this item. Further impetus was given to 
 whole-grain corn by the perfecting of can-closing machines which 
 sealed cans in a high vacuum. This invention permitted canning the 
 so-called "dry pack" or "vacuum pack" a product more nearly like 
 fresh corn than any other. The effect of these inventions was revolu- 
 
 *These numbers refer to literature citations on page 355. 
 
 279 
 
280 BULLETIN No. 466 [May, 
 
 tionary; by 1937 about 30 percent of all the corn packed was whole- 
 grain style. 
 
 Popular preference has turned since about 1930 in the direction of 
 yellow varieties of sweet corn over the white types. In 1938 more than 
 half the total pack of sweet corn and about 80 percent of the whole- 
 grain pack was yellow. The numbers of cases" of the different kinds 
 of corn packed in 1936, 1937, and 1938 were as follows: 
 
 1936 1937 1938 
 
 Total pack, all types 14,621,189 23,541,224 20,469,518 
 
 Cream style, white 5,635,960 9,701,301 7,345,957 
 
 Cream style, yellow 4,947,010 7,493,909 7,624,369 
 
 Whole-grain style, white 1,148,920 1,459,634 1,158,729 
 
 Whole-grain style, yellow 2,890,560 5,668,206 4,717,787 
 
 When this change in preference toward yellow sweet corn began to 
 take place, ordinary Golden Bantam was the most suitable yellow 
 variety available. Inasmuch as canners had previously been interested 
 chiefly in the white types, breeders had paid very little attention to the 
 yellow. Golden Bantam, however, being very susceptible to bacterial 
 wilt, is suitable only for northern climates and is not particularly well 
 adapted to Illinois. 
 
 In 1931 G. M. Smith 15 * introduced a yellow first-generation hybrid 
 (Purdue 39 X 51) under the name of Golden Cross Bantam. Practi- 
 cally coinciding with the introduction of the whole-grain cutter and the 
 vacuum-pack process, this cross met a very insistent demand. Used 
 more or less wherever sweet corn is packed, it is now the most widely 
 grown sweet-corn hybrid in use today. Demand for seed of this cross 
 has compelled seedsmen to learn how to produce hybrids on a large 
 scale. Golden Cross Bantam has also demonstrated that good hybrids 
 are adapted over a surprisingly wide range of climate and soils. 
 
 Any remaining doubts which corn breeders may have had were 
 dispelled by the severe drouths of 1934 and 1936, which demonstrated 
 that crosses give the greatest comparative increases in yields over open- 
 pollinated strains under the most severe conditions. 
 
 Despite numerous tests, however, and considerable commercial 
 experience with hybrids, the full behavior of crosses under actual field 
 conditions is still imperfectly understood. Very little is known re- 
 garding such questions as regional adaptability of crosses, the ultimate 
 effect of inbreeding for many generations, and the merits of single 
 crosses as compared with other types. Furthermore, little actual infor- 
 mation is available regarding the means of successfully maintaining 
 superior inbred lines. 
 
 "Twenty-four No. 2 cans per case. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 281 
 
 At the Illinois Agricultural Experiment Station breeding work 
 with sweet corn was begun in 1922. At first the work was confined to 
 Country Gentleman and Narrow Grain Evergreen varieties, but in 
 1930 yellow varieties were included. During the eighteen years of 
 breeding work thru 1939, more than a thousand inbred selections were 
 made and more than four thousand crosses were tested. From among 
 all these, twelve inbred lines have been released to the seed trade, and 
 the crosses of the earliest releases, made in 1935, have come into 
 extensive use. It is the purpose of the present bulletin to describe the 
 inbreds which have been released and their use in crosses, and to dis- 
 cuss in addition some of the problems of inbreeding and crossing upon 
 which light has been thrown by the experimental breeding work and 
 the commercial production of both the inbreds and the crosses. 
 
 ADVANTAGES OF SINGLE CROSSES 3 
 
 The true value of single crosses to the grower appeared during the 
 severe drouths of 1934 and 1936, when it became apparent that a 
 well-adapted cross had a smaller variation in annual yields than open- 
 pollinated strains. In open-pollinated sweet corn the range in yields 
 from season to season is from less than 1 to more than 4 tons of 
 unhusked ears to the acre. The superiority of the crosses in this 
 respect is shown by the six years' results of yield tests at the Illinois 
 Station summarized in Table 1. The annual yield variation is indicated 
 by the coefficient of variability, which for Cross 8X6 was consistently 
 less than for the open-pollinated strains for all the yield components 
 except cans per gross ton, in which component there was practically no 
 difference. 
 
 Differences in yield of prime cut kernels (percentage basis) be- 
 tween the cross and the open-pollinated check in Table 1 were largest 
 in the most adverse seasons (1931, 1933, 1934, and 1936) and least 
 during the favorable seasons (1935 and 1937). Thus as an indication 
 of the value of a cross, its performance in a favorable year is not as 
 good a criterion as its performance in an adverse season. 
 
 Differences very similar to those in Table 1 also appear in tests of 
 
 'Unstandardized genetic terms have caused much confusion. The terms 
 "single cross," "first-generation hybrid," "cross" and even "hybrid" are used 
 interchangeably by most writers. For a cross between two inbred lines, the term 
 "single cross" is preferred, and is used here. The term "top cross" means a 
 cross between an open-pollinated seed parent and an inbred line. "Hybrid" is 
 used here as a general term to denote crosses of all kinds, collectively. 
 
282 
 
 BULLETIN No. 466 
 
 [May, 
 
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 Prime cut kernels 
 
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 ii^ls 2,. 
 
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 Prime husked ears 
 
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 ISSRSS SS5 
 
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 ^^"^"^ (N OJ 
 
 Unhusked ears 
 
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 (9 
 
 H feO 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 283 
 
 field-corn hybrids. In the performance trials of Dungan et al** in 
 northern Illinois in the drouth year 1934, four good hybrids averaged 
 20.2 bushels more sound corn per acre than the five best open-pollinated 
 varieties, but in 1935, a more favorable year for growing corn, the 
 four hybrids averaged only 10.9 bushels more per acre than the open- 
 pollinated varieties. The four hybrids averaged 67.2 bushels per acre 
 in 1934 and 87.8 bushels in 1935, and the open-pollinated varieties 
 averaged 47.0 bushels in 1934 and 76.9 bushels in 1935. 
 
 Annual yield differences as variable as these have deceived corn 
 breeders in the past and will most likely deceive corn growers in the 
 future. Crosses should be considered as a form of crop insurance, 
 producing in favorable years only slightly more than open-pollinated 
 varieties, but holding up much better than the open-pollinated varieties 
 when growing conditions are unfavorable. 
 
 NATURE OF INCREASED YIELDS OF 
 SWEET-CORN CROSSES 
 
 In the yield performance of several thousand sweet-corn crosses 
 over a period of twelve years, the single crosses and open-pollinated 
 strains did not differ as much in yields of unhusked ears as in yields 
 of cut corn. The yields of husked ears tended to be intermediate 
 between the two. This relationship is obvious in the following data on 
 yields of Cross 8X6 (six-year-averages, Table 1): 
 
 Increase over 
 
 open-pollinated Percent 
 checks increase 
 
 Unhusked ears, per acre . 488 ton 18.6 
 
 Husked ears, per acre . 538 ton 33 . 9 
 
 Prime cut kernels, per acre . 282 ton 41 . 8 
 
 No. 2 cans, per acre 25 . 6 cases 41 . 8 
 
 Recovery per gross ton 123 cans 22 . 6 
 
 This behavior may be explained by the fact that a single cross is 
 much more uniform in maturity than open-pollinated strains. The total 
 harvest of unhusked ears may be nearly the same, but the recovery 
 of edible kernels from the single cross is much higher (41.8 percent 
 as compared with 18.6 percent in the foregoing example) owing to the 
 fact that there is less variation in the maturity of the cross. Therefore 
 a ton of unhusked ears from a cross is worth more than a ton from 
 an open-pollinated strain. The difference as shown in the above 
 example was 22.6 percent in favor of the cross. 
 
 The fact that only relatively small increases in weights of unhusked 
 
284 BULLETIN No. 466 [May, 
 
 ears may be expected from a cross, especially in a favorable season, 
 is explained as follows: Weight of unhusked ears depends of course 
 on (1) the number of ears and (2) the size or weight of each ear. 
 Under favorable conditions a good open-pollinated strain will produce 
 about the same number and the same size of ears as the cross, and 
 the total yields will therefore tend to be the same. However, as Huelsen 
 and Michaels 9 * have pointed out, altho weights of unhusked ears are 
 closely associated with weights of prime cut kernels, they are not an 
 accurate means of determining the yields of prime cut kernels. Thus 
 similarity in yields of unhusked ears does not necessarily mean 
 equivalent recovery of cut kernels or canned corn. 
 
 REGIONAL ADAPTABILITY OF CROSSES' 
 
 In cooperative tests over a seven-year period involving several 
 thousand sweet-corn crosses of various types, the yield performance at 
 Urbana frequently failed to be duplicated in northern Illinois. Many 
 of the more promising crosses, however, were in fair agreement in the 
 two regions. 
 
 Experience gained from these tests, as well as from actual com- 
 mercial production of crosses, indicates that in order to be successful 
 a single cross must possess a considerable range of adaptability. There 
 is very good reason to believe that crosses which are merely local in 
 adaptability will prove to be equally limited in adaptability to the usual 
 changes in weather in one locality. 
 
 Effect of Source of Seed. One phase of adaptability not under- 
 stood at present is the effect of source of seed (region in which the seed 
 is grown) on the performance of crosses grown from it. 
 
 Jones and Huntington, 11 * in discussing the relation between corn 
 yields and climate, stated that "corn may be moved from a less favor- 
 able to a more favorable climatic region without loss of productive 
 capacity and usually with distinct gain." Experience has shown not 
 only that this is true, but, what is more important, that when corn is 
 moved from a more to a less favorable climate there is a loss in pro- 
 ductive capacity. In numerous tests at the Illinois Station sweet-corn 
 hybrids of eastern origin have failed to produce as well as the native 
 open-pollinated strains used for comparison. This raises the question 
 whether the quality of a cross originating in an unfavorable climate 
 will deteriorate by raising the seed in a more favorable section. 
 
 For the production of sweet-corn seed there are two exceptionally 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 285 
 
 favorable locations in the United States one along Long Island Sound, 
 in Connecticut, and the other in the Boise River Valley of Idaho, from 
 Nampa, Idaho, northwest to Ontario, Oregon. Most of the hybrid 
 sweet-corn seed now offered commercially is being grown in these 
 sections. 
 
 According to personal observations by the author, radical changes 
 in the appearance of inbreds developed in Illinois are likely to occur 
 when they are grown in the different climates of either Idaho or Con- 
 necticut, particularly under the irrigated farming of Idaho. The 
 changes in those grown in Connecticut were relatively slight. When 
 inbreds originating in Illinois were brought back after only one 
 generation in Idaho or Connecticut, the changes were very obvious. 
 There was a definite increase in height in almost all inbreds, and some 
 lines showed definite tendencies toward segregation altho selfed for 
 twelve or more generations. After two generations away from Illinois 
 these changes became more pronounced. Inbreds themselves differed 
 widely in this respect. 
 
 The full effect of such changes in inbreds on single crosses is not 
 now known. Long-continued tests will be necessary to determine, for 
 example, the extent to which a single cross adapted to Illinois will 
 maintain its drouth-resistance and other desirable characters if the 
 inbreds are grown continuously in the more favorable climate existing 
 in the seed-producing sections of the West. Enough data on this point 
 have been gathered, however, to point strongly to the conclusion that 
 the crosses will deteriorate if the inbreds are grown continuously in 
 the more favorable climate. The more progressive seedsmen have 
 given up the idea, for the present at least, of maintaining inbreds in 
 Idaho and Connecticut. 
 
 The effects of maintaining Illinois Country Gentleman inbreds in 
 various sections on the yields of the crosses tested at Urbana are 
 shown in Table 2. Yields of crosses made in Idaho from inbreds main- 
 tained there show great deterioration. The reductions were not due 
 to outcrossing or to mixtures. 
 
 A more striking example of the effects of the favorable climate of 
 Idaho on the yields of a single cross is shown by the results listed in 
 Table 3. The parent inbreds of these crosses, Purdue 39 and Purdue 
 51, originated in Indiana. The inbreds were highly selected and care- 
 fully maintained by a good Idaho seed grower, but the yields 
 deteriorated rapidly nevertheless, in spite of the fact that the seed for 
 the 1934, 1935, and 1936 seed was 3, 2, and 1 year old, respectively, 
 when tested in 1937 and 4, 3, and 2 years old when tested again in 1938. 
 
286 
 
 BULLETIN No. 466 
 
 [May, 
 
 TABLE 2. DETERIORATION OF ILLINOIS COUNTRY GENTLEMAN INBREDS MAIN- 
 TAINED AND CROSSED IN OTHER STATES AND RETURNED TO ILLINOIS 
 
 
 
 
 
 
 Percent increase in weight 
 
 
 Number of 
 
 
 
 
 of prime cut kernels 
 
 Cross 
 
 years main- 
 tained away 
 from 
 Illinois* 
 
 Where cross 
 was made 
 
 Year tested 
 at Urbana 
 
 Number of 
 replications 
 
 Over open- 
 pollinated, 
 Illinois 
 
 Over cross 
 8X6, 
 Illinois 
 
 
 
 
 
 
 grown 
 
 grown 
 
 8 X6 
 
 
 
 Illinois 
 
 1937 
 
 25 
 
 34.2 
 
 
 
 2 
 
 Connecticut 
 
 1937 
 
 5 
 
 30.5 
 
 
 
 2 
 
 Idaho 
 
 1937 
 
 5 
 
 - 6.0 
 
 
 8 X6 
 
 3 
 
 Idaho 
 
 1938 
 
 5 
 
 
 -27.5 
 
 
 3 
 
 Idaho 
 
 1938 
 
 5 
 
 
 -11.0 
 
 8 X6 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 
 -32.5 
 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 
 -15.6 
 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 , 
 
 -22.7 
 
 5 X 10 
 
 
 
 Illinois 
 
 1937 
 
 5 
 
 40.1 
 
 
 
 2 
 
 Connecticut 
 
 1937 
 
 5 
 
 15.3 
 
 
 5 X10 
 
 
 
 Illinois 
 
 1938 
 
 5 
 
 
 - 1.6 
 
 
 3 
 
 Idaho 
 
 1938 
 
 5 
 
 
 - 5.0 
 
 
 3 
 
 Idaho 
 
 1938 
 
 5 
 
 
 - 7.8 
 
 5 X10 
 
 
 
 Illinois 
 
 1939 
 
 5 
 
 
 8.9 
 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 
 -15.6 
 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 
 -28.7 
 
 3 X6 
 
 
 
 Illinois 
 
 1937 
 
 6 
 
 7.2 
 
 
 
 2 
 
 Iowa 
 
 1937 
 
 5 
 
 - 5.6 
 
 
 
 2 
 
 Idaho 
 
 1937 
 
 5 
 
 7.4 
 
 
 3 X6 
 
 3 
 
 Idaho 
 
 1938 
 
 5 
 
 
 - 7.5 
 
 
 3 
 
 Iowa 
 
 1938 
 
 5 
 
 
 - 8.6 
 
 3 X6 
 
 4 
 
 Idaho 
 
 1939 
 
 S 
 
 
 -36.4 
 
 
 2 
 
 Minnesota 
 
 1939 
 
 5 
 
 
 -24.4 
 
 
 4 
 
 Idaho 
 
 1939 
 
 5 
 
 
 -32.6 
 
 "At the time the inbreds were released, in 1935, the lines removed from Illinois for maintenance 
 elsewhere were identical with the respective lines continued in Illinois. 
 
 Theoretically, such changes should not occur in a homozygous 
 inbred line, but on the other hand it is likely that these lines are not 
 truly homozygous. It is probable that as a result of continued selfing 
 the line eventually becomes a mixture of pure phenotypes. Since there 
 are no visible differences in the plants or ears to show the presence of 
 these phenotypes, the breeder in his own trial grounds can do little or 
 nothing to reduce their number. A radical change in climate (change 
 in photoperiod and mean temperature) may, however, bring out these 
 hitherto latent or invisible characters. Several examples illustrate this 
 point. 
 
 Examples of Latent Characters Revealed by Change of Climate. 
 One example was afforded by IllinoFs Country Gentleman Inbred 8, 
 which has a number of outstanding morphological characters that make 
 
1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 287 
 
 identification easy, and which is unusually uniform after seventeen 
 generations of inbreeding. Inasmuch as Inbred 8 has been grown for 
 seed on hundreds of acres in Illinois over a period of seven years, its 
 behavior in Illinois is understood. Only occasionally does it produce 
 tassel ears in Illinois. In Idaho, however, even from seed grown in 
 Illinois, Inbred 8 produced a large number of tassel ears. Moreover, 
 about 75 percent of the ears grown in Idaho had staminate inflores- 
 cences (rudimentary tassels) growing at the end of the cob, a char- 
 acter which never appears in Illinois. It was possible in 1937 to 
 examine for these characters corn growing from the same lot of seed 
 
 TABLE 3. PROGRESSIVE DETERIORATION IN YIELDS OF GOLDEN CROSS BANTAM 
 
 RESULTING FROM MAINTAINING THE INBREDS IN IDAHO 
 
 (Averages of 5 replications with Illinois-grown checks planted every fifth row. Checks 
 are averages of 15 replications. All tests were made at Urbana.) 
 
 
 Number of 
 years in- 
 breds were 
 maintained 
 in Idaho 
 
 Yields when grown in Illinois 
 
 Test in 
 1937 
 
 Percent 
 decrease 
 under 
 check 
 
 Test in 
 1938 
 
 Percent 
 decrease 
 under 
 check 
 
 Sorted unhusked ears 
 From Illinois seed (check)* 
 
 
 tons 
 3.808 
 
 3.379 
 2.923 
 2.826 
 
 2.622 
 
 2.304 
 2.017 
 1.925 
 
 1.378 
 
 1.234 
 1.088 
 1.049 
 
 11.3 
 23.2 
 25.8 
 
 12.1 
 23.1 
 26.6 
 
 10.4 
 21.0 
 23.9 
 
 tons 
 5.189 
 
 4.626 
 4.204 
 4.486 
 
 3.030 
 
 2.621 
 2.553 
 2.682 
 
 1.481 
 
 1.350 
 1.307 
 .947 
 
 10.9 
 19.0 
 13.6 
 
 13.5 
 15.7 
 11.5 
 
 8.8 
 11.7 
 36.0 
 
 From Idaho seed 
 Crossed in 1934 
 
 2 
 3 
 4 
 
 Crossed in 1935 
 
 Crossed in 1936 
 
 Prime husked ears 
 From Illinois seed (check)* 
 
 From Idaho seed 
 Crossed in 1934 . 
 
 2 
 3 
 4 
 
 Crossed in 1935 
 
 Crossed in 1936 
 
 Prime cut kernels 
 From Illinois seed (check)* 
 
 From Idaho seed 
 Crossed in 1934 
 
 2 
 3 
 4 
 
 Crossed in 1935 . 
 
 Crossed in 1936 
 
 
 Seed designated as "Illinois seed" was a cross of inbred lines maintained in Illinois and crossed 
 the year preceding the making of the yield test. 
 
 both in Illinois and in Idaho the same season. Two seasons of selection 
 in Idaho were sufficient to eliminate the tassel at the end of the cob. 
 
 Another example of hidden or invisible characters being brought 
 out by change of climate occurred in Illinois Country Gentleman 
 Inbred 3 and Illinois Narrow Grain Evergreen Inbred 13. Both of 
 these lines have medium-length shanks when grown in Illinois, but in 
 Idaho they segregate for excessively long shanks. 
 
288 BULLETIN No. 466 [May, 
 
 BREEDING METHODS USED 
 Selection Within Inbred Lines 
 
 Description of System Used. The principal method followed in the 
 sweet-corn breeding program at the Illinois Station has been that 
 known as "selection within inbred lines," as described by Richey. 13 * 
 The parent materials at the beginning of the Illinois program consisted 
 of 200 ears of Country Gentleman and 100 ears of Narrow Grain 
 Evergreen contributed by two canners who had grown their stocks in 
 Illinois for several years and had used mass-selection methods. Seed 
 from the ears was planted in individual ear-rows, yields were taken, 
 and the conventional method of ear-row selection followed thruout 
 the work. A duplicate planting of each row served for the purpose of 
 inbreeding or selfing that is, the artificial fertilization of individual 
 ears by applying pollen from the tassel to the ear of the same plant, 
 suitable protection being obtained by means of paper sacks. The inbred 
 or selfed ears were planted the following year, as shown in Fig. 1. 
 Selected plants were again selfed, and so on. Practically no sib-crossing 
 has been used in the selection work. 
 
 The system shown in Fig. 1 is an adaptation of the old ear-row 
 method, using selfed ears as the parents. This is a highly intensive 
 method of breeding and is open to at least two objections. The first 
 is that selections must be discarded very freely in order to prevent a 
 rapid increase in the number of lines ; but on the other hand there is a 
 corresponding advantage of confining contaminations and segregations 
 of undesirable characters to single rows where elimination is simple. 
 The second objection is that the range of selection is narrowed by 
 limiting the available germ plasm at the start. A possible third objec- 
 tion may be based on the assumption that after several generations 
 many of the inbreds will be more or less closely related to each other. 
 
 There seems to be no one best method of carrying on a breeding 
 program ; consequently each breeder usually works out his own pro- 
 cedure. The method outlined in Fig. 1 gives the opportunity of inten- 
 sive selection within relatively few inbred lines. In practice more new 
 lines are selected each year out of the ear-row open-pollinated selection 
 program which is carried on parallel to the inbreeding. 
 
 Effects of the Method on the Inbreds. The extent to which selec- 
 tion within inbred lines may be carried with some prospect of improve- 
 ment still remains an open question. All of the inbred lines discussed 
 in this bulletin have been broken down into numerous sib lines, a but 
 
 "Offspring from the same parents. 
 
194Q~\ 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 289 
 
 FIG. 1. OUTLINE OF METHOD USED IN SWEET-CORN BREEDING 
 
 1ST YEAR 
 
 EAR -ROWS FOR 
 YIELD TEST 
 
 ABCDEFGHI 
 
 DUPLICATES FOR 
 
 SELFING 
 
 20 YEAR 
 
 ABCDEFGHI 
 
 B.B.B.B.B, 
 \ 
 
 3D 1 
 4TH| 
 5TH| 
 6THJ 
 
 YEARS 
 
 Ear-rows planted in duplicate, one planting 
 harvested as a yield test and the duplicate 
 rows selfed. The best selfed rows, on the 
 basis of the yield test, carried into the next 
 year. 
 
 Inbred ears from the highest yielding ear- 
 rows of the first year planted in ear-rows and 
 selfed, and the best of these, selected on the 
 basis of appearance and ear-tests for disease 
 and germination, carried into the third year. 
 
 Selections from previous year's planting of 
 ear-rows planted in ear-rows and selected 
 again in the same manner as previously. 
 
 7 TH YEAR 
 
 EXPERIMENTAL 
 
 RECIPROCAL 
 SINGLE CROSSES 
 
 Reciprocal crosses made between all the sur- 
 viving sibs of inbred lines, only those lines 
 being crossed that were not related to each 
 other in any way. 
 
 Crosses tested and selected on basis of com- 
 parisons with the best open-pollinated ear-row 
 selections carried on parallel with the inbreed- 
 ing. Selections within the best-surviving in- 
 bred lines continued as before and carried on 
 indefinitely. 
 
 11 TH YEAR 
 
 Reciprocal crosses of the surviving inbred lines 
 made in isolation plots. (For most seed 
 growers the making of reciprocal crosses by 
 hand is likely to be more practical than the 
 use of isolation plots.) 
 
 12TH1 
 13THJ 
 
 YEARS 
 
 REPLICATED YIELD 
 TESTS OF RECIPRO- 
 CAL SINGLE 
 CROSSES 
 
 Yield and quality tests of the reciprocal 
 crosses made to eliminate finally all but the 
 most promising inbred lines. 
 
290 BULLETIN No. 466 [May, 
 
 improvement beyond a certain point, as measured by the yield per- 
 formances of the crosses, is very difficult. Continued selection within 
 an inbred line usually improves its physical appearance and frequently 
 the yield of seed can be materially increased. However, in the process, 
 the yield of the cross may be seriously impaired. There are various 
 theoretical considerations on which an explanation may be based, but 
 this matter need not be discussed here. 
 
 The effect of selection in inbred lines on yield of the crosses is 
 shown in Table 4. All five of the selections out of Inbred 8 were 
 superior in appearance and vigor to the original strain, but the 
 original release maintained for six generations in isolation gave the 
 highest average yield for the group (97.32 percent). None of the 
 crosses of the selections within Inbreds 8 and 6 gave yields significantly 
 higher than that of the commercial Cross 8X6 used as the check. 
 
 Some of the eighty crosses of the selections within Inbreds 5 and 
 10 were more promising. Of the eighty, however, those from only six 
 selections of Inbred 5 gave higher yields than the cross using the 
 originally released Inbred 5, and of those six only three gave sub- 
 stantially higher yields. Thus not much progress was made toward 
 improving the yields of the crosses by means of selection within the 
 inbred lines. In fact, selection within inbred lines based on physical 
 characters of plants and ears is just as likely to reduce the yields of 
 the crosses as to increase them. The probabilities of increasing yields 
 of crosses by such methods seem to be much more promising in a con- 
 stantly varying line such as Inbred 5 than in a highly stable line such 
 as Inbred 8. Similarly the selections within the somewhat variable 
 Inbred 10 give better results than selections within the more stable 
 Inbred 6. 
 
 Altho the data have been omitted from Table 4, the corn produced 
 by each of the crosses was canned and graded, and the quality of the 
 canned corn was just as variable as the yields. Furthermore, the corn 
 from the higher yielding crosses was frequently sharply lower in 
 quality than the corn from the check. 
 
 Tests such as those reported in Table 4 indicate that there is no 
 known reliable criterion for selecting within inbred lines. Scrubby- 
 looking selections may prove to be superior to the best-looking ones in 
 the group. The most practical method seems to be to select both the 
 apparently desirable and the apparently undesirable types and to check 
 back by means of crossing and canning. This method of selection is 
 facilitated by selfing plants individually, avoiding sib crosses so far as 
 possible. Selfing individual plants has been followed for eighteen 
 
ILLINOIS SWEET-CORX INBREDS AND CROSSES 
 
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 generations at the Illinois Station. The data in Table 4 show that the 
 degree of homozygosity attained so far as the quantitative genes are 
 concerned is not very high that for Inbred 5, for example, is very low 
 indeed. 
 
 Selfing of Desirable Crosses 
 
 Theoretically, if Cross A X B is selfed, the resulting mbreds will 
 have the good qualities of either A or B predominating, plus a portion 
 of those contributed by the other parent. 
 
 In actual practice numerous crosses have been selfed for as many 
 as twelve generations, and the resultant inbred lines have resembled 
 one or the other of the parents without showing any superiority as 
 determined by yields in a series of crosses. In view of the disappoint- 
 ing results, this method of breeding has not been included in 1 the system 
 of breeding outlined in Fig. 1. 
 
 Back-Crossing 
 
 Continuous back-crossing has also been followed, using Narrow 
 Grain Evergreen Inbred 14 as the pollinator. Even tho very diverse 
 material was used, including Country Gentleman, the results are of 
 questionable value, as there is no evidence that any of the back crosses 
 when used as parents in single crosses were superior to the original 
 Inbred 14 in yield performance. 
 
 Possible Deterioration in Inbred Lines 
 
 The system of inbreeding outlined in the foregoing paragraphs has 
 one defect in common with all the other methods which have been 
 proposed there is no certainty that a high level of yield and quality 
 once established by inbreeding can be maintained. 
 
 Experience has shown that inbred lines reach their prime after 
 about ten generations of selfing. If a line inbred to that extent fails 
 to give good crosses, it is certain that no amount of further selection 
 will change this performance. In a line which does cross well, it is 
 equally certain by the laws of chance alone, that slight improvements 
 can be effected, but that they cannot go on indefinitely. 
 
 From the way in which inbreds in general behave, there would 
 seem to be a slight tho constant decrease in vigor in successive gener- 
 ations, which will most likely affect the crosses sooner or later. From 
 their behavior in crosses, there is reason to believe that inbred lines 
 have a period of development followed by one of senescence. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 293 
 
 Most breeders are aware of this danger of deterioration. Various 
 methods of sib-crossing have been proposed to forestall possible de- 
 terioration, but there is no proof so far that such procedures are any 
 more successful than the constant selfing, selection, and testing of 
 crosses previously discussed. 
 
 Since knowledge of inbred behavior is so slight, the advisable 
 course seems to consist in constant selection followed by sib-crossing 
 in the multiplication plots and the crossing of selections within inbred 
 lines with similar selections in the paired inbred. There is considerable 
 evidence that the behavior of inbred selections, such as those in Table 4, 
 can be materially changed by pairing selections. In other words, 
 certain selections will nick better than others. It may be possible by 
 such methods to maintain productiveness and quality in the crosses, 
 but there is no positive proof of this at the present time. 
 
 WHAT CONSTITUTES A GOOD INBRED LINE 
 
 Two criteria are used in determining the value of an inbred: it 
 must produce well, and it must give desirable crosses. If an inbred 
 is low-yielding but gives superior crosses, it must be used as the pollen 
 parent; and it therefore needs to have good tassel characters. A 
 familiar example is P 39 X PSI (Golden Cross Bantam), in which P 5 i, 
 because of low seed yields, is always used as the pollen parent. 
 
 Two low-yielding inbreds may produce a high-yielding cross, but 
 because of the high seed cost such a combination has little commercial 
 value. The ideal cross would seem to be a combination of two high- 
 yielding inbreds, but in actual practice the best combinations usually 
 consist of a highly desirable inbred line combined with one more or 
 less mediocre, the latter serving as the pollen parent. 
 
 In propagating pairs of inbreds such as these, the breeder is 
 tempted to "improve" the mediocre line by selection. Results such as 
 those in Table 4 will most likely follow unless adequate precautions 
 are taken. 
 
 TWELVE INBRED LINES RELEASED 
 
 As the result of the breeding work outlined in the foregoing sec- 
 tions, certain inbred lines have proved to be consistently superior 
 when used in single crosses. The yield trials on which these conclusions 
 are based and a description of the crosses are given in Table 5 and on 
 pages 326 to 352. Eight Country Gentleman and four Narrow Grain 
 
294 BULLETIN No. 466 [May, 
 
 Evergreen inbred lines have been released to several seedsmen under 
 certain restrictions. The released lines are as follows: 
 
 Number of Number of 
 
 generations inbred, generations inbred, 
 
 thru 1939 thru 1939 
 
 Illinois Country Gentleman Illinois Narrow Grain Evergreen 
 
 Inbred 1 17 Inbred 11 17 
 
 Inbred 3 15 Inbred 13 17 
 
 Inbred 5 15 Inbred 14 17 
 
 Inbred 6 17 Inbred 55 15 
 
 Inbred 10 17 
 
 Inbred 8 17 
 
 Inbred 9 15 
 
 Inbred 15 15 
 
 Crosses between these lines were first made in 1928, since which 
 time certain combinations have come into commercial use in Illinois 
 and elsewhere. 
 
 Inbred 9, originally released, was dropped later, as it proved to 
 be inferior to the sib-line 8, and Inbreds 1 and 15 have been withdrawn 
 from commercial production. The eight lines of Country Gentleman 
 were crossed in all possible combinations, barring those that were 
 related. These crosses were tested for yield and canning quality in 
 1933 and 1934, two very unfavorable drouth years, at Urbana and in 
 northern Illinois. Only the Urbana results are discussed here, inasmuch 
 as the data obtained in northern Illinois supported conclusions similar 
 to those based on the Urbana data. 
 
 The tests were conducted on a dark prairie silt loam of moderate 
 fertility which was manured the previous fall. No commercial 
 fertilizers were used. A medium amount of phosphorus was available. 
 The crosses were planted at random, 38 by 38 inches apart in 1933 and 
 40 by 40 inches in 1934. Each plot consisted of 20 hills in a single 
 row, with checks planted every fifth row. No attempt was made to 
 correct for the border effect, which cannot be avoided with single rows. 
 However, since the crosses did not differ materially in plant size, the 
 border effect could not have been very significant. That the border 
 effect was not very significant was indicated further by the fact that 
 the results of the northern Illinois tests, which were on a three-row 
 basis per plot, with only the center row being harvested, led to the 
 same conclusions. 
 
 Five replications were planted each year, but owing to adverse 
 weather in 1933 one or more replications of many of the crosses had 
 to be discarded because of poor stand. In 1934 the tests were repeated 
 with the same lots of seed, and owing to better conditions in the spring 
 practically no plots were discarded because of stand. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 295 
 
 The plots were planted 4 to 5 kernels per hill and thinned down to 
 3 as soon as the seedlings reached a height of 4 inches. The checks 
 were planted with seed obtained from the highest yielding strain out 
 of open-pollinated ear-row selections continuously selected since 1922. 
 Only the most perfect ears were used for planting the checks, the 
 choice being made on the bases of appearance and the results of testing 
 each ear in a germinator for viability and freedom from rots and molds. 
 Such ears were butted and tipped before shelling, but were not run 
 thru a grader. The hybrid seed was merely shelled without butting or 
 tipping and without testing in the germinator. The experimental bias 
 was therefore strongly against the hybrids, which had to be very 
 vigorous indeed to overcome this initial handicap. 
 
 The corn was harvested in a single picking from each row at the 
 prime canning stage. All the ears were snapped and sorted later into 
 usable ears and culls. The usable unhusked ears were husked in a 
 husking machine and were again sorted into prime canning ears and 
 nonusable ears, which are called "husked culls." The prime husked 
 ears were then run thru a Sprague No. 5 corn-cutter and the weights 
 recorded in terms of cream-style cut. 
 
 Results of Yield Tests With Single Crosses 
 
 The yield tests for 1933 and 1934 at Urbana were averaged (Table 
 5) and the increases in yields over the nearest checks were compared 
 without making any other corrections for soil heterogeneity. The 
 significance of the mean increases in yields were determined according 
 to the methods described in Chapter V of Fisher's work on statistical 
 methods. 6 * Comparisons of two mean differences were made on the 
 basis of the formula stated by Burgess: 3 * 
 
 S.E. 2 /S.E. 2 
 S.E.M.O. = 
 
 Probability was determined from the value t according to Table IV of 
 Fisher's work. 6 * Mean differences were not considered significant when 
 the values of P exceeded .05. 
 
 Many of the crosses yielded significantly more than the checks 
 (Table 5). These differences were used as the basis for selecting the 
 crosses to be propagated commercially. 
 
 The crosses listed in Table 5 were paired as far as possible with 
 their reciprocals. Many of the pairs themselves showed significant 
 differences in yield. These differences have been critically analyzed. 
 
296 
 
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1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
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302 BULLETIN No. 466 [May, 
 
 Classification of Crosses 
 
 Classification Based on Selectivity. On the basis of the character- 
 istics of their parents, the single crosses listed in Tables 5, 6, and 7 fell 
 into three classes: compatible, incompatible, and antagonistic. Com- 
 patible crosses are those which are made in the proper direction with 
 selective inbred lines, that is, a selective female by a selective male. 
 Incompatible crosses are those made in the wrong direction, that is, a 
 selective male inbred line used as a female by a selective female inbred 
 used as a male. Antagonistic crosses are made between similarly selec- 
 tive parents, that is, a selective male by a selective male, or a selective 
 female by a selective female. 
 
 The basis for making such a classification is the data in Table 5 
 grouped and averaged according to parental lines in Table 6. According 
 to Table 6, Inbreds 1, 2, 4, 6, and 10 all showed more or less tendency 
 to be selectively male. In Inbreds 1 and 6 this tendency was statisti- 
 cally significant with regard to certain yield components. 
 
 Inbreds 3, 5, 7, 8, and 9, on the other hand, tended to be selectively 
 female, Inbreds 5, 7, and 9 significantly so in certain instances, assum- 
 ing that for a large number of degrees of freedom any value of t as 
 great as or exceeding 1.95996 is significant, since according to Fisher 6 * 
 this value is equivalent to the 5-percent point where n = oo . It should 
 be noted that Inbreds 6 and 10, closely related lines, are both selectively 
 male, while Inbreds 8 and 9, also related, are selectively female. 
 
 Yields of compatible and antagonistic crosses are given in Table 7. 
 The increases in yields were computed from the differences in yield 
 between the reciprocal crosses recorded in Table 5. These differences 
 were then listed in two groups compatible and antagonistic. The fol- 
 lowing example shows how the computations were made, using the 
 yields of cut kernels of Inbred 8, which is selectively female: 
 
 Compatible Crosses (Inbred 8 Antagonistic Crosses (Inbred 8 used as female 
 used as female) with a selective female used as a male) 
 
 Tons Tons 
 
 8 X 1 greater than 1 X 8 by. . .191 8 X 3 greater than 3 X 8 by. .- .070 
 
 8 X 2 greater than 2 X 8 by. . .067 8 X 5 greater than 5 X 8 by. .- .040 
 
 8X4 greater than 4 X 8 by. . - .001 8X7 greater than 7 X 8 by . . .057 
 8 X 6 greater than 6 X 8 by.. .071 Mean =- .018 .036 
 
 8X10 greater than 10X8 by .052 
 
 Mean = .055 + .036 
 
 The difference between the compatible and antagonistic crosses in this 
 example equals .073 .051 0= 1.431) tons. 
 
 The results, according to the data listed in Table 7, were somewhat 
 irregular, and in addition nearly all the values of t were too small to 
 
1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
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 BULLETIN No. 466 
 
 a 
 
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 Indicated use 
 of inbred 
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 Female 
 
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 - 
 
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 increases, 
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 female* 
 
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 1 1 1 1 
 
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 Mean in- 
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 ills 
 
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 Ear component 
 
 
 
 
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 DfXUU 
 
 Unhusked ears 
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 Culls, husked 
 Cut kernels 
 
 Unhusked ears 
 Prime husked ears. . 
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 Unhusked ears 
 Prime husked ears. . 
 Culls, husked 
 Cut kernels 
 
 Degrees 
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1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
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306 
 
 BULLETIN No. 466 
 
 [May, 
 
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1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 307 
 
 show significant differences. The inconsistencies were due to Inbreds 
 2, 4, and 7, all of which have been discarded because of low yields 
 (Table 5). Many of the comparisons involving these three inbreds were 
 between decreases rather than increases in yields, as compared with the 
 yields of the open-pollinated checks. 
 
 The other seven inbreds, however, were consistent in their tenden- 
 cies, agreeing with field experience in making these crosses on a com- 
 mercial scale. 
 
 On a genetic basis crosses and their reciprocals should be the same. 
 Aside from considerations of seed quality discussed by Ashby 1 ' 2 * and 
 Sprague, 17 * the yields should be approximately equal. The data in 
 Tables 5, 6 and 7 indicate, however, that the plant breeder is justified 
 in assuming that crosses and their reciprocals will not give the same 
 performance. In numerous instances reciprocal crosses differed sig- 
 nificantly in yields (Table 5), a tendency confirmed by observations 
 made on a large number of additional crosses. 
 
 Possible Causes for Differences in Yields of Reciprocals. Many of 
 the differences in the yields of reciprocals in Table 5 may be ascribed 
 to physiological causes. For instance, in crossing an inbred susceptible 
 to ear rots with one partially resistant, reciprocals would be expected 
 to show yield differences, inasmuch as one cross would produce seed 
 having a high initial infection, whereas the other would be relatively 
 free. 
 
 Differences in seed size undoubtedly explain some of the yield 
 differences between reciprocal crosses. Thus when it is used as the 
 seed parent, Inbred 6, which has extremely small kernels, produces a 
 weaker plant and lower yield and matures later than its reciprocal 
 (Table 12, page 320). This is in accordance with Ashby's 1 * third postu- 
 late, that reciprocal crosses differing in embryo weight should differ 
 in degree of vigor. Sprague, 17 * using later generations of Ashby's 
 material, was able to substantiate this postulate only partially, finding 
 that seed having small embryos was later in maturity than that having 
 large embryos, but that the growth rate was not significantly different. 
 In the work reported here (Table 5) the differences in yield were not, 
 however, due to differences in maturity. Differences in maturity were 
 compensated by harvesting at the same relative canning stage, using 
 silk counts as the basis, according to methods described by Huelsen 
 and Michaels. 9 * 
 
 In order to determine further whether size of seed of Inbred 6 
 is the factor involved in producing lower yields, a reciprocal cross was 
 made in Idaho in 1938 between Inbreds 8 and 6 because when Inbred 
 
308 BULLETIN No. 466 {.May, 
 
 6 is grown there the kernels are considerably larger and freer from 
 disease than when produced in Illinois. The reciprocal crosses were 
 tested in 1939 at Urbana in five trials paired with Cross 8 X 6 as 
 the check grown from seed produced in Illinois. The mean weights, 
 expressed as percentages of the check, were: 
 
 Cross 8X6 Cross 6X8 
 
 Sorted unhusked ears 81 .45 66. 78 
 
 Prime husked ears 79 . 37 65 .45 
 
 Prime cut kernels 77 . 27 61.11 
 
 Cross 6X8 was thus again consistently lower in yield than Cross 
 8X6. Something besides size of seed probably is involved. 
 
 Reasons for Selectivity of Inbreds. The tendency for Inbreds 1, 
 2, 4, and 10 (Table 6) to be selectively male cannot, however, be ex- 
 plained satisfactorily on the basis of seed size, none of them having 
 the abnormally small kernels which characterize Inbred 6. In fact 
 Inbred 4 is selectively male in spite of having excellent seed quality and 
 poor tassels. Inbred 10, which is closely related to Inbred 6 but has 
 larger kernels, is also selectively male without a satisfactory explana- 
 tion. Inbred 1 is selectively male perhaps because, as explained later, 
 it has weak germination due to some unknown factor. 
 
 In the selectively female group (Table 6), Inbreds 3 and 5 have 
 poor tassels, which may have something to do with their preference ; 
 but in contrast Inbreds 8 and 9 which are closely related have ex- 
 ceptionally good tassels. Inbreds 5, 8, and 9 have large seed, but 
 Inbred 3 has relatively small seed. 
 
 It is quite obvious in view of these facts that the selectivity of an 
 inbred is a matter to be seriously considered by the breeder. The 
 data are insufficient, however, to determine whether selectivity is due 
 to individual strain peculiarities, or to response to some law of genetics 
 or physiology. The evidence from these experiments points in the 
 direction of strain idiosyncrasy. 
 
 Selectivity of Inbreds in Relation to 
 the Breeding Program 
 
 The significant yield differences between reciprocal crosses 
 (Table 5) show that an inbred can be properly evaluated only when 
 its selectivity as to male or female use is definitely known. Selectivity 
 can be determined by making a series of reciprocal crosses and com- 
 paring the yields (Table 6). 
 
 The most successful crosses are compatible, and the breeder can 
 save considerable time by limiting his crossing program to this type. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 309 
 
 Antagonistic and incompatible crosses should in general be avoided, 
 altho certain exceptions will undoubtedly appear. For example, 
 Cross 1X6, which is antagonistic since both inbreds are selectively 
 male, was used commercially and was dropped only because of con- 
 sistently poor germination. Cross 3 X 8 is another antagonistic cross 
 having commercial value, but it is not as good as certain others in the 
 group and was finally dropped in 1938. 
 
 EVALUATING ILLINOIS COUNTRY GENTLEMAN 
 
 INBREDS 
 
 The inbred lines discussed in this bulletin (both the Country Gentle- 
 man inbreds, and the Narrow Grain Evergreen inbreds discussed on 
 pages 322 to 326) were first evaluated on the basis of physical char- 
 acters, yields, and uniformity, but as soon as approximate hymozygosity 
 was attained, their usefulness had to be determined. In other words, 
 potential value had to be converted into actual value by performance 
 as parents in crosses. Actual value can best be determined by crossing 
 an inbred line with a series of others and averaging the performance 
 of the crosses. 
 
 Evaluation on Basis of Yields 
 
 The levels of performance of the inbred lines were calculated by 
 averaging the yield increases over their respective open-pollinated 
 checks of all the crosses, including reciprocals, in which each inbred 
 was used as a parent. The mean increases thus obtained are a measure 
 of the productivity of a given inbred in crosses and have been con- 
 sistently used in the sweet-corn breeding work at the Illinois Station. 
 
 After calculating the mean increases for each inbred it was possible 
 to make direct comparisons of inbreds with each other (Table 8, see 
 footnote 6). 
 
 Inbreds 2, 4, 7, and 16 are obviously poorer than the others as in- 
 dicated by the preponderance of minus signs in their respective 
 columns in Table 8. With the exception of husked culls Inbred 4 
 showed no increases, indicating that its performance was the poorest 
 of any of the inbreds. Inbreds 2, 7, and 16 were not quite as poor as 
 Inbred 4, but it will be noted under their respective columns in Table 8 
 that the only increases recorded were over one or more of the other 
 inbreds in this group of four low yielders (Inbreds 2, 4, 7, and 16). 
 
 The inferior performance of the top crosses is shown in Table 8 
 under the column headed "open pollinated." Except for husked culls 
 
310 
 
 BULLETIN No. 466 
 
 [May, 
 
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1940~\ 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 311 
 
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312 BULLETIN No. 466 [May, 
 
 the only increases were over the four lowest yielding inbreds, namely 
 Inbreds 2, 4, 7, and 16. 
 
 The performance of Inbred 3 was also very mediocre, practically 
 the only increases being over the inferior Inbreds 2, 4, 7, and 16, 
 and the top crosses. Inbred 3 was not discarded, however, as were 
 Inbreds 2, 4, 7, and 16, but was retained because in certain limited 
 combinations it proved to have some value. 
 
 The remaining lines, Inbreds 1, 5, 6, 8, 9, 10, and 15, all showed 
 more or less promise (Table 8), as indicated by the small number of 
 significant decreases in their respective columns. 
 
 Mean differences such as those in Table 8 are also useful in calling 
 attention to gene characters which are transmitted to the crosses, 
 evidently being dominant because of their appearance in the F\ gener- 
 ation. For instance, Inbreds 5 and 8 showed a strong tendency to 
 produce large yields of unhusked ears but a relatively low recovery 
 of cut kernels, a fact which has been substantiated by their performance 
 in numerous additional crosses. 
 
 In contrast, Inbred 15 (Table 8) gave a high recovery of cut 
 kernels, as indicated by the preponderance of increases in yields of 
 prime cut kernels, and a relatively low yield of unhusked ears, as 
 shown by the numerous minus signs in that column. This character- 
 istic of Inbred 15 has been checked in numerous additional crosses 
 both experimental and commercial. 
 
 These differences in yield performance show the danger of attempt- 
 ing to determine the value of crosses or of inbreds on the basis of 
 data on only a single yield component. The value of the different 
 yield components as bases for evaluating inbreds is discussed in the 
 next section. 
 
 The data in Table 8 are open to criticism because reciprocals are 
 included even tho it has been shown that the lines are either selec- 
 tively male or selectively female. The yields were also compared as 
 far as possible with reciprocals eliminated, but the results are not 
 given here, inasmuch as they do not change the conclusions reached 
 from the data as given in Table 8. 
 
 Relative Values of Various Yield Components. The yield charac- 
 teristics of the crosses in which the several inbreds were used as 
 parents are further analyzed in Table 9 for the purpose of determining 
 the relative values of the various yield components as a basis for 
 judging the performance of inbred lines. According to Table 9, the 
 percentage differences between prime cut kernels and prime husked 
 ears were small and only three of them were significant. On the other 
 
1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 313 
 
 TABLE 9. RELATIVE PERFORMANCE OF INBRED LINES DETERMINED BY AVERAGING 
 
 THE 1934 MEAN YIELDS OF EACH CROSS IN WHICH THE RESPECTIVE INBREDS 
 
 APPEARED AS PARENTS AND COMPARING THEM BY YIELD COMPONENTS 
 
 (The value / was determined by dividing the mean increases 
 
 by the respective standard errors) 
 
 Inbred 
 No. 
 
 Degrees 
 of 
 freedom 
 
 Prime husked ears 
 compared with 
 unhusked ears 
 
 Prime cut kernels com- 
 pared with prime 
 husked ears 
 
 Prime cut kernels 
 compared with 
 unhusked ears 
 
 Mean 
 difference* 
 
 / 
 
 Mean 
 difference" 
 
 / 
 
 Mean 
 difference* 
 
 t 
 
 1 
 
 20 
 20 
 19 
 20 
 19 
 18 
 20 
 18 
 18 
 18 
 10 
 10 
 11 
 
 28.39 
 14.40 
 28.48 
 3.63 
 21.90 
 34.55 
 17.39 
 20.98 
 24.24 
 29.58 
 39.76 
 38.82 
 19.42 
 
 5.91* 
 3.36* 
 7.76* 
 1.11 
 4.67* 
 6.84* 
 5.24* 
 6.01* 
 5.96* 
 7.13* 
 7.54* 
 7.66* 
 4.77* 
 
 2.97 
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 -10.90 
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 .59 
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 .58 
 .38 
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 .21 
 .44 
 1.40 
 
 30.98 
 12.91 
 23.08 
 1.53 
 11.63 
 34.36 
 17.50 
 22.48 
 25.30 
 18.68 
 40.45 
 39.65 
 13.91 
 
 6.41* 
 2.86* 
 5.86* 
 .46 
 2.14* 
 7.67* 
 3.96* 
 4.74* 
 4.49* 
 4.47* 
 7.51* 
 8.18* 
 2.49* 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 .... 
 
 8 
 
 9 
 
 10 
 
 15 
 
 16 
 
 Top cross b .... 
 
 'Values of / indicate P is less than .05, hence difference is significant. 
 
 The differences between the mean yields of the five replications of each cross and their respec- 
 tive checks were calculated as percentages of the checks (check = 100 percent). These percentages 
 were averaged on the basis of the parents; that is to say, all the crosses in which Inbred 1, for example, 
 was a parent were averaged together. The same thing was done with the other inbreds. The mean 
 percentages for each inbred were then compared in three groups as shown (prime husked ears with 
 sorted unhusked ears, et cetera) and the mean differences between these percentages recorded in 
 the proper columns. The direction which these mean percentage differences take is indicated by 
 the column headings, the first stated component greater than the last (prime husked ears greater 
 sorted unhusked, et cetera. 
 
 b Open-pollinated strain used as female parent in twelve top crosses. 
 
 hand, the differences between prime cut kernels and unhusked ears 
 were large, and all but one were significant. This is interpreted to 
 mean that the weights of prime cut kernels can be estimated with much 
 greater accuracy from the weights of prime husked ears than from 
 the weights of sorted unhusked ears. Similarly the large significant 
 differences between weights of prime husked and sorted unhusked 
 ears indicate that the yield of the latter component may not be used 
 to predict the yield of the former. These results with crosses parallel 
 the conclusions reached by Huelsen and Michaels 8 * in work with open- 
 pollinated varieties of sweet corn. 
 
 Relative Percentages of Recovery and Waste. Only the data for 
 1934 on relative percentages of recovery and waste are given 
 (Table 10), as the 1933 figures do not change the conclusions. Because 
 1933 and 1934 were very severe drouth years, the base (normal re- 
 covery of open-pollinated Country Gentleman sweet corn) given in 
 Table 10 is higher than the recovery of the open-pollinated Country 
 Gentleman checks. Altho the performance of the inbreds was also 
 
314 
 
 BULLETIN No. 466 
 
 [May, 
 
 TABLE 10. RELATIVE PERCENTAGES OF RECOVERY AND WASTE OF COUNTRY 
 GENTLEMAN INBREDS USED IN SINGLE CROSSES, 1934 
 
 Inbred No. 
 
 Number of 
 crosses 
 averaged* 
 
 1 ton unhusked ears = 100 percent 
 
 1 ton prime husked 
 ears = 100 percent 
 
 Prime 
 husked 
 ears 
 
 Husks 
 
 Prime cut 
 kernels 
 
 Husks and 
 cobs 
 
 Prime cut 
 kernels 
 
 Cobs 
 
 1 
 
 20 
 19 
 19 
 19 
 19 
 18 
 20 
 18 
 18 
 18 
 10 
 10 
 12 
 ( e ) 
 
 perct. 
 55.90 
 51.78 
 51.26 
 42.96 
 49.03 
 58.10 
 53.34 
 55.95 
 57.28 
 58.33 
 59.39 
 59.69 
 52.33 
 41.56 
 
 60 
 
 perct. 
 44.10 
 48.22 
 48.74 
 57.04 
 50.97 
 41.90 
 46.66 
 44.05 
 42.78 
 41.67 
 40.61 
 40.31 
 47.67 
 58.44 
 
 40 
 
 perct. 
 21.04 
 18.20 
 17.82 
 14.99 
 17.28 
 21.11 
 19.71 
 20.51 
 21.08 
 20.26 
 22.19 
 21.87 
 18.32 
 15.11 
 
 30 
 
 perct. 
 78.96 
 81.80 
 82.18 
 85.01 
 82.72 
 79.89 
 80.29 
 79.49 
 78.92 
 79.74 
 77.81 
 78.13 
 81.68 
 84.89 
 
 70 
 
 perct. 
 37.63 
 35.14 
 34.77 
 34.90 
 35.24 
 36.33 
 36.94 
 36.66 
 36.81 
 34.73 , 
 37.36 
 36.63 
 35.01 
 36.36 
 
 50 
 
 perct. 
 62.37 
 64.86 
 65.23 
 65.10 
 64.76 
 63.67 
 63.06 
 63.34 
 63.19 
 65.27 
 62.64 
 63.37 
 64.99 
 63.64 
 
 50 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 . . 
 
 9 
 
 10 
 
 15. .. 
 
 16 
 
 
 Checks 
 
 Base d 
 
 
 
 Each cross replicated five times. 
 
 KJpen-pollinated Country Gentleman used as the female in top crosses with the twelve inbreds 
 listed. 
 
 c Open-pollinated Country Gentleman used as checks; averages of 100 replications. 
 
 d The base is the normal performance of open-pollinated Country Gentleman sweet corn in 
 Illinois. See Huelsen and Michaels. 8 * 
 
 below par, only Inbred 4 gave as low a percentage of prime husked 
 ears as the open-pollinated checks. 
 
 Prime cut kernels (basis: weight of prime husked ears = 100 
 percent, Table 10) were relatively uniform compared with the other 
 yield components. This further indicates that if accurate yield records 
 of sweet-corn crosses are desired, the yields of the edible portion of the 
 ear must be the basis of comparison. From the genetic standpoint the 
 relative uniformity of this yield component is important because it 
 indicates that none of the inbred lines deviate very much from open- 
 pollinated sweet corn in weight of cobs. Individual crosses do, of 
 course, show considerable variation in this respect. 
 
 The prime husked ears and prime cut kernels (basis: weight of 
 unhusked ears = 100 percent, Table 10) both showed wide variations 
 due mostly to the large differences in the percentages of husks, thus 
 further confirming the unreliability of yields of unhusked ears as a 
 basis for estimating other yield components. According to Huelsen 
 and Michaels, 9 * the best way to determine the yield of prime cut kernels 
 is to actually secure the cut-off records, tho the yields of prime husked 
 ears of the open-pollinated varieties with which that work was done 
 were in sufficiently close correlation to serve commercially as a basis 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 315 
 
 for prediction purposes. In these studies of inbreds and crosses the 
 relative yields of prime husked ears and of prime kernels differed 
 significantly (Table 9) in three of thirteen inbred lines. It is doubtful, 
 therefore, whether inbreds can be evaluated with sufficient accuracy 
 on any other basis than yields of cut kernels. 
 
 Evaluation on Basis of Quality 
 
 Yield should not be the only basis for evaluating inbred lines and 
 crosses. Quality is equally important. A really successful cross com- 
 bines high yield with high quality. 
 
 Method of Classification. In these experiments quality was 
 measured by means of actual canning tests conducted in cooperation 
 with one of the Illinois canning companies. Since defects in quality 
 in the Country Gentleman variety are most evident when it is packed 
 whole-grain style, this was the style of cut used. In 1933, corn from 
 each of the crosses was packed in 12-ounce cans with brine, but in 
 1934 the vacuum pack with only a small addition of brine was used. 
 
 The canned corn was sampled during the winters of 1933-34 and 
 1934-35 according to the then current commercial practice. The samples 
 were rated on the following points, the sequence of the numbers show- 
 ing the order of preference: 
 
 Color 
 
 1. White (not due to over- maturity)] 
 
 2. Trace of brown > Color good 
 
 3. Slightly brown (slightly dark) 1 
 
 4. Brown (dark) Color acceptable 
 
 5. Gray j 
 
 6. Yellow tinged | Off color, not acceptable 
 
 7. Yellow caps J 
 
 Flavor 
 
 1. Excellent 3. Good 5. Poor 
 
 2. Very good 4. Fair 6. Very poor 
 
 Toughness 
 
 1. Very tender (extra fancy) 4. Slightly tough (extra standard) 
 
 2. Tender (fancy) 5. Tough (standard) 
 
 3. Fairly tender (fancy minus) 6. Very tough (substandard) 
 
 Width of kernels 
 
 1. Very small 3. Medium-small 5. Medium-large 
 
 2. Small 4. Medium 6. Large 
 
 Length of kernel (depth of cut) 
 
 1. Very deep 4. Medium-good 6. Medium-shallow 
 
 2. Deep 5. Medium 7. Shallow 
 
 3. Good 
 
316 BULLETIN No. 466 [May, 
 
 The commercial grades of canned corn (extra fancy, fancy, extra 
 standard, standard, and substandard) were determined for each cross 
 but are not discussed inasmuch as the purpose of the study was to de- 
 termine the nature of any inherent defects associated with the inbreds 
 and crosses. 
 
 Results. Two to four lots of each cross were canned in 1933, but 
 in 1934 only the more promising crosses were canned, and those were 
 canned in duplicate. The frequency distributions of the readings are 
 given in Table 11. These should be regarded merely as indicative, 
 because in packing a large number of small samples errors due to 
 differences in maturity and slight variations in the method of packing 
 were bound to occur even tho all possible precautions were taken. 
 Maturities were estimated on the basis of silk counts and the -corn was 
 harvested accordingly. 
 
 The discrepancies in total numbers of samples of the same inbred 
 in the different sections of Table 11 (for example, 21 samples of In- 
 bred 1 were tested for color and 39 for flavor) were due to the fact 
 that for some samples no reading was taken of certain characters 
 because of defects due apparently to variation in the method of packing. 
 The much lower totals recorded under the color readings in 1933 were 
 due to the elimination of replicate samples and the recording of only 
 the best reading of each group. It is assumed that when the corn is 
 packed from four replicates of a cross, the sample showing the best 
 color is the one most truly representative. 
 
 None of the inbreds showed conspicuously uniform color defects. 
 Especially in 1933 some crosses showed a tinge of yellow, an undesir- 
 able character in Country Gentleman sweet corn. The white color 
 of some of the samples was not due to over-maturity. 
 
 As to flavor, all of the inbreds produced crosses which in 1933 
 had flavor lower than "good," but in this respect they were no worse 
 than open-pollinated Country Gentleman. None of the inbreds except 
 Inbred 4 could be singled out on the basis of flavor. Inbred 4 had a 
 distinctive popcorn-like flavor different from that of any other Country 
 Gentleman line. 
 
 Several inbreds could be singled out on the basis of pericarp charac- 
 ter (Table 11). Crosses in which Inbreds 4, 6, 8, and 15 were used had 
 a noticeably tender pericarp. None of the inbreds, however, consist- 
 ently produced tough crosses, altho some of them, Inbreds 1 and 2 for 
 example, produced a considerable number of tough crosses in 1933. 
 
 In kernel character the inbreds showed wide differences (Table 11). 
 Inbreds 4, 6, and 10 produced predominantly slender kernels, but none 
 
1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 317 
 
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 BULLETIN No. 466 
 
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1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 319 
 
 was characterized by unusually wide kernels. Kernel length ranged 
 mostly from medium to good, but all the lines produced some crosses 
 having deep kernels and other crosses having shallow kernels. In 
 none of them did "deep kernels" constitute the modal class. The rela- 
 tively wide spread in kernel depth indicates that this character, if 
 hereditary, is probably only partially dominant. For instance, Inbred 1, 
 which has long kernels, produced one cross in 1933 having shallow 
 kernels, but Inbred 6, which also has long kernels, produced four 
 crosses having shallow kernels. On the other hand Inbred 4, which has 
 shallow kernels, produced in 1933 a total of five crosses having "good" 
 or "deep" kernel depth. 
 
 The frequencies for 1933 listed in Table 11 are of value, however, 
 in indicating the strain tendencies, which may be summarized as 
 
 follows: Percent of Percent of 
 
 crosses deeper crosses deeper 
 
 than medium than medium 
 
 Inbred 1 65.8 Inbred 3 37.5 
 
 Inbred 10 59.4 Inbred 2 37.1 
 
 Inbred 6 51.4 Inbred 9 37.1 
 
 Inbred 15 50.0 Inbred 16 23.8 
 
 Top crosses 45 . 4 Inbred 4 12.2 
 
 Inbred 5 41.7 Inbred 7 10.5 
 
 Inbred 8 40.0 
 
 Evaluation on Basis of Maturity 
 
 . Maturity was estimated on the basis of silk counts, by the method 
 described by Huelsen and Michaels. 9 * The relative lengths of time 
 from planting to maturity of the inbreds (averages of crosses in which 
 the inbreds were used) in comparison with the respective open- 
 pollinated checks are given in Table 12. 
 
 Most of the inbreds were earlier than the checks, but it should be 
 noted that here again the various strains were selective according to 
 their use, many being earlier when used in compatible crosses. Inbreds 
 2, 3, 5, 6, 8, and 9 all showed this trend. Since compatibility was de- 
 termined by the yield, it follows that with these six inbreds good yields 
 and earliness were associated. In Inbreds 5, 6, 8, and 9 this trend may 
 have been due to a third factor, seed size. Inbreds 5, 8, and 9 are 
 selectively female and have large seed; and Inbred 6 is selectively 
 male, and has very small seed. In Inbreds 2 and 3 the gains in earliness 
 were slight and, moreover, not consistent. Inbreds 4 and 10 gave 
 contradictory results. Inbreds 1 and 7, of which the incompatible 
 crosses w r ere the earlier, showed a trend contrary to that shown by 
 Inbreds 2, 3, 5, 6, 8, and 9. 
 
320 
 
 BULLETIN No. 466 
 
 [May, 
 
 TABLE 12. COMPARATIVE TIME TO MATURITY OF INBRED LINES USED IN CROSSES, 
 
 MEASURED BY MEAN NUMBER OF DAYS EARLIER OR LATER* THAN 
 
 RESPECTIVE OPEN-POLLINATEP CHECKS, 1933-1934 
 
 Inbred No. 
 
 19 
 
 33 
 
 1934 
 
 
 
 Used as female 
 
 Used as male 
 
 Used as female 
 
 Used as male 
 
 1 
 
 days 
 .44 
 
 days 
 1.38 
 
 days 
 - .33 
 
 days 
 
 
 2 . 
 
 .10 
 
 .10 
 
 14 
 
 83 
 
 3 
 
 - .73 
 
 - .67 
 
 1.10 
 
 .31 
 
 4 
 
 -1.38 
 
 -1.00 
 
 
 
 .57 
 
 5. 
 
 80 
 
 .62 
 
 .17 
 
 .60 
 
 6 
 
 - .30 
 
 -1.40 
 
 - .50 
 
 - .80 
 
 7 
 
 -1.60 
 
 -1.90 
 
 - .86 
 
 -1.20 
 
 8 
 
 .27 
 
 1.00 
 
 
 
 .62 
 
 9 
 
 .30 
 
 3.00 
 
 .43 
 
 .80 
 
 10 
 
 1 90 
 
 1 30 
 
 .12 
 
 .20 
 
 15 
 
 
 -2.27 
 
 
 .40 
 
 16 
 
 
 -3.82 
 
 
 - .18 
 
 Top cross 1 " .... . . . 
 
 58 
 
 
 .33 
 
 
 
 
 
 
 
 lor Inbreds 15 ana lo ana the open-poiiinatea cnecks, wnere ten to twelve crosses or replicates wer 
 averaged. The means thus calculated were subtracted from the mean number of days obtained froi 
 the accompanying checks. 
 
 b Open- pollinated Country Gentleman used in top crosses. 
 
 Apparently seed size is an important factor involved in the time 
 required for maturing. Accordingly, it would seem advisable when 
 making crosses in actual practice, to use the larger-seeded parent as 
 the seed parent so far as possible. This practice would tend to increase 
 the earliness of maturity, but not necessarily the yields. 
 
 Evaluation on Basis of Individual Ear Weights 
 
 Weight per husked ear is an important factor in evaluating the 
 crosses produced by any inbred line, as even a small increase here 
 will afford a substantial saving in manufacturing costs. The per- 
 formance of the several inbred lines in these studies with respect to 
 mean weights per prime husked ear is given in Table 13. Performance 
 was calculated on the basis of use in crosses, there being substantial 
 differences in 'some cases according to whether the inbred was used as 
 male or as female. 
 
 Inbreds 1, 2, 6, 8, and 10 which, with the exception of Inbred 8, 
 were selectively male (Table 6), produced, on the average, larger 
 ears when used as male parents. In contrast, Inbreds 5, 7, and 9, all 
 selectively female, had larger ears on the average when used as seed 
 parents. Inbreds 3 and 4 showed no such differences. Annual results 
 were not always in agreement with these average tendencies. 
 
 These observations further confirm previous conclusions regarding 
 
1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 321 
 
 TABLE 13. MEAN* WEIGHTS PER PRIME HUSKED EAR, PERCENTAGE BASIS 
 (Weight of check-plot ears = 100 percent) 
 
 Inbred No. 
 
 1933 
 
 1934 
 
 Average 
 
 Used as 
 female 
 
 Used as 
 male 
 
 Used as 
 female 
 
 Used as 
 male 
 
 Used as 
 female 
 
 Used as 
 male 
 
 1 
 
 perct. 
 109.2 
 91.6 
 101.1 
 86.1 
 110.5 
 105.1 
 98.7 
 100.4 
 102.6 
 96.2 
 
 perct. 
 113.8 
 91.9 
 99.7 
 90.8 
 107.7 
 104.2 
 96.5 
 102.1 
 98.7 
 103.1 
 104.6 
 88.8 
 
 perct. 
 111.2 
 86.4 
 99.2 
 85.4 
 108.7 
 103.3 
 97.3 
 98.8 
 98.0 
 102.6 
 
 109^2 
 
 perct. 
 111.3 
 100.8 
 102.0 
 80.4 
 105.9 
 107.6 
 92.5 
 99.9 
 96.0 
 105.1 
 106.6 
 91.5 
 
 perct. 
 110.2 
 89.0 
 100.2 
 86.0 
 109.6 
 104.2 
 98.0 
 99.6 
 100.3 
 99.4 
 
 104.7 
 
 perct. 
 112.5 
 96.4 
 100.8 
 85.6 
 106.8 
 105.9 
 94.5 
 101.0 
 97.4 
 104.1 
 105.6 
 90.2 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10. . 
 
 15 
 
 16 
 
 
 Top cross b 
 
 100.2 
 
 
 The mean percentages are averages of at least 10 crosses each replicated five times and com- 
 pared with an equal number of checks. Each percentage is therefore the mean of at least 50 plots. 
 The weight per ear for each plot was calculated by dividing the total weight of prime husked ears 
 by the total number of such ears produced. 
 
 b Open-pollinated Country Gentleman used in top crosses. 
 
 selectivity of inbred lines. In general the larger ears are associated 
 with compatible crosses. 
 
 Evaluation on Basis of Smut Frequency 
 
 Since from the canner's viewpoint smut is highly objectionable on 
 ears of sweet corn, inbreds which are susceptible to smut must be 
 used in crosses only with caution. Five of the inbreds (Inbreds 2, 6, 
 7, 10, and 16) showed considerable smut in these tests, and in addition 
 the frequency of smut on the top crosses was high (Table 14). Inbred 
 9 showed an exceptionally small percentage of smut, and Inbreds 4, 
 5, 8, and 15 showed slightly higher amounts. The latter five strains 
 may therefore be considered relatively free from this disease, especially 
 as there was practically no severe smut in crosses utilizing any of them. 
 
 General Evaluation of Inbred Lines 
 
 The performance of the inbred lines both as to yield and as to 
 quality is summarized in Table 15. Inbreds 2, 7, and 9 did not have a 
 great deal to recommend them in comparison with some of the others. 
 Inbred 4, altho low in yield, was exceptional in the quality of its 
 crosses, the canned corn being characterized by a flavor very similar 
 to that of freshly roasted popcorn, quite unlike any other Country 
 Gentleman strain. Inbreds 6 and 10 were acceptable in spite of their 
 
322 
 
 BULLETIN No. 466 
 
 [May, 
 
 TABLE 14. NUMBER OF PLOTS ON WHICH EVIDENCES OF SMUT WERE FOUND ON 
 HUSKED EARS OUT OF CROSSES, CLASSIFIED BY INBRED LINES, 1934 
 
 Inbred No. 
 
 Number of 
 plots 
 observed* 
 
 Number of plots 
 where smut was 
 
 Total plots 
 on which 
 smut was 
 observed 
 
 Percentage 
 
 Slight 
 
 Considerable 
 
 1 
 
 120 
 120 
 120 
 120 
 120 
 120 
 120 
 110 
 110 
 120 
 55 
 55 
 55 
 
 19 
 36 
 18 
 13 
 13 
 21 
 23 
 13 
 6 
 20 
 6 
 9 
 14 
 
 4 
 3 
 2 
 2 
 
 8 
 13 
 
 
 8 
 
 4 
 
 
 23 
 39 
 20 
 
 15 
 13 
 29 
 36 
 13 
 6 
 28 
 6 
 13 
 15 
 
 19.2 
 32.5 
 16.7 
 12.5 
 10.8 
 24.2 
 30.0 
 11.8 
 5.5 
 23.3 
 10.9 
 23.7 
 ,27.3 
 
 2 ... 
 
 3 
 
 4 . 
 
 5 
 
 6 
 
 7 ... 
 
 8 
 
 9 
 
 10 
 
 15 
 
 16 . . 
 
 Top cross 1 " 
 
 
 Each cross was replicated five times and the total number of plots involved is the number of 
 crosses X 5. "Slight smut" means that only a few ears in each plot were infected; "considerable 
 smut" means that the percentage of ears having smut was high. 
 
 b Open-pollinated Country Gentleman used in top crosses. 
 
 susceptibility to smut, but in using them care must be taken to cross 
 them with relatively smut- free types. 
 
 Top crosses with open-pollinated Country Gentleman did not com- 
 pare favorably with crosses from most of the inbred lines, and con- 
 sequently the use of such top crosses is not considered acceptable. 
 
 The canning quality of the inbreds as determined by use in crosses 
 did not show much variation, according to Table 15. None of the in- 
 breds in the group had consistently poor quality. It should be under- 
 stood in this connection that this group of inbreds was selected from 
 more than a hundred lines, as those having the most promise. Poor 
 quality would have been indicated by underlying defects in the pre- 
 liminary tests made to select the better inbreds. Inasmuch as the 
 quality ratings in Table 15 are summaries, individual crosses may of 
 course be much higher or much lower in quality than indicated there. 
 
 NARROW GRAIN EVERGREEN INBREDS AND CROSSES 
 
 Discussion of Narrow Grain Evergreen inbreds in this bulletin is 
 limited to four lines (Inbreds 13 and 14 released in 1935 and Inbreds 
 11 and 55 released in 1939) which have proved to be the best in a 
 considerable group of Narrow Grain Evergreen strains. Since in Illi- 
 nois this variety has become of relatively minor importance in compari- 
 son with Country Gentleman, it is not considered necessary to enter into 
 many details regarding yield tests by means of which the various lines 
 
ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 323 
 
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 e 
 
 5- 
 
 U I. 
 
 rt eg 
 
 u u 
 
 n o ^ 
 
 01 01 
 
 
 85 D 
 
 >> >> u 
 
 >> X >i >. 
 
 Maturity, 
 with c 
 (Tabl 
 
 E E_M_M'^'^ 
 
 b t E Ofl W 
 
 w55((/5ttfl 
 
 n 
 
 ^ r*? 
 
 oi H 
 
 1-111 
 
 S.JlA.kttJIJ 
 
 i 
 
 6 
 7 
 
 
 o 
 
 I 
 
 ^ 
 
 ::::::::::::& 
 
 
 A 
 
324 BULLETIN No. 466 [May, 
 
 were successively eliminated until only Inbreds 11, 13, 14, and 55 
 remained. 
 
 The methods of breeding and of testing the crosses were the same 
 as those used with Country Gentleman. A summary of the trials is 
 given in Table 16. Four Narrow Grain Evergreen crosses (14X 13, 
 11 X 13, 11 X 14 and 11 X 55) w r ere tested for periods varying from 
 three to nine years. Altho these four crosses differ in type, the yields 
 of cut kernels showed practically the same increases over the open- 
 pollinated checks, varying only from 43.7 to 49.3 percent (Table 16). 
 This consistency is surprising, because for only two of the crosses were 
 the yields entering into the averages obtained during the same series 
 of years. 
 
 Narrow Grain Evergreen Inbred 14 has been crossed commercially 
 to a limited extent with Country Gentleman Inbreds 6 and 10 (Figs. 
 18 and 19, pages 349 and 350), producing an intermediate type having 
 husked ears as large as the straight Narrow Grain Evergreen crosses, 
 but yielding somewhat less cut corn (Table 16). The kernels of Crosses 
 14 X 10 and 14 X 6 are somewhat more slender and have slightly 
 better quality in the can than straight Narrow Grain Evergreen crosses, 
 but cannot, however, be classed as Country Gentleman according to 
 Huelsen and Gillis. 8 * Usually Crosses 14 X 10 and 14 X 6 segregate to 
 some extent for ears having more or less of a zigzag kernel 
 arrangement. 
 
 Choice between Narrow Grain Evergreen crosses is more likely to 
 be based on ear type and size than on slight yield differences. Data 
 on numbers of rows of kernels and length of fill on the cobs are there- 
 fore included (Table 17). This test was conducted in central In- 
 diana thru the cooperation of a seedsman. As to numbers of rows of 
 kernels, Cross 14 X 13 had few ears with more than 18 rows, but 
 most of the ears of Cross 11 X 13 had from 18 to 20 rows, those of 
 Cross 11 X 55 had from 18 to 22 rows. Cross 11 X 14 was intermedi- 
 ate, with most of the ears having 16 to 18 rows. The lack of uniformity 
 of the open-pollinated strain is shown by the wide variation in numbers 
 of rows ranging from 14 to 24. 
 
 In length of fill of kernels on the cob Cross 14 X 13 was somewhat 
 shorter than the other three crosses, according to this test in Indiana 
 (Table 17). This finding was not, however, in accordance with the 
 data given in Table 16. Ordinarily the four crosses may be arranged 
 11 X 13, 11 X 55, 14 X 13, and 11 X 14 in order of decreasing length 
 per ear, but this varies with soil and season. Ear length was definitely 
 much less variable in the crosses than in the open-pollinated check. 
 
1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 325 
 
 OPEN-POLLINATED STRAIN OF SAME VARIETY 
 
 (Figures indicate percentage increase over open-pollinated checks") 
 
 Weights of 
 prime cut 
 kernels 
 
 t- <N <S fj "5 "5 
 
 The best open-pollinated Station strain was used as the check, the seed being ear-tested for germination and freedom from disease, but the crosses were not 
 so tested. 
 ^Commercial seedsman's stock for both years of 14 X 10 and in 1937 and 1939 for 14 X o. 
 
 t5 00 "I t~ O- * 
 ^ s t5 TJ< Tf T) 
 
 Weights of prime husked ears 
 
 Total culls 
 
 m*f*O TJ<(S\O 
 
 \r>t^o*O*~* 00 
 ts^ fS ^O'O 
 III II 
 
 Per ear 
 
 w;O^OvOO 
 
 vOfNt^Tf O 
 
 V 
 
 3 
 
 i 
 
 1 
 
 H 
 
 MTt O'OfCOO 
 
 vovoi^ "tin 
 
 WN'>'5 CS 
 
 Weights of unhusked ears 
 
 Total culls 
 
 O": ts>n o>oo 
 
 WOfSOO mr^ 
 -4 rt f^ CSfS 'J' 
 
 1 1 1 1 
 
 Per ear 
 
 * * -O O> fl 00 
 
 ts t- rs cs -H 10 
 
 - 1 1 
 
 Total usable 
 
 \ri tsmO'f f> 
 
 OnO1^ l '^fO 
 
 Number of 
 tests 
 averaged 
 
 -O"T^>O * 
 t^ ^H r^ cs PC rN 
 
 Years tested 
 
 
 
 
 3 : : : : 
 
 r~ 
 
 vO 
 
 
 
 <* ;ovoo : : 
 c^r 1 1^ i^ oo oo 
 
 ^- OO^HOI^I^ 
 
 O'^'">')'O 1 C 
 
 o\ao>o>ova 
 
 
 O 
 
 5O J f)Tn 
 ~*\O~~*<r> 
 
 xxxxxx 
 
 ______ 
 
 
326 
 
 BULLETIN No. 466 
 
 [May, 
 
 TABLE 17. FREQUENCY DISTRIBUTIONS SHOWING PERCENTAGES OF TOTAL NUMBER 
 OF EARS OF FOUR NARROW GRAIN EVERGREEN CROSSES AND AN OPEN-POLLI- 
 NATED CHECK CLASSIFIED AS TO NUMBER OF Rows AND LENGTH 
 OF FILL ON THE EARS, 1939 TEST IN CENTRAL INDIANA 
 
 Cross 
 
 Frequency distribution, percent of total number of ears 
 having number of rows indicated 
 
 12 rows 
 
 14 rows 
 
 16 rows 
 
 18 rows 
 
 20 rows 
 
 22 rows 
 
 24 rows 
 
 Not 
 classified* 
 
 14 X 13 
 
 2.5 
 
 14.3 
 
 55.4 
 26.4 
 6.6 
 
 5.5 
 
 21.1 
 
 18.5 
 51.2 
 37.7 
 24.6 
 
 28.6 
 
 3.4 
 14.4 
 42.6 
 36.6 
 
 18.3 
 
 3.2 
 4.9 
 23.8 
 
 16.5 
 
 ".8 
 7.1 
 
 4.6 
 
 5.9 
 4.8 
 6.6 
 2.4 
 
 8.2 
 
 11 X 14 . 
 
 11 X 13. ... 
 
 
 .8 
 
 11 x 55 
 
 
 Open-pollinated 
 check 
 
 
 2.7 
 
 
 
 
 Frequency distribution, percent of total number 
 of ears whose lengths 1 " were ' 
 
 4-5 inches 
 
 5-6 inches 
 
 6-7 inches 
 
 7-8 inches 
 
 8-9 inches 
 
 14 X 13... 
 
 .2.5 
 2.2 
 1.2 
 1.1 
 
 4.1 
 
 20.0 
 3.3 
 7.1 
 10.1 
 
 12.3 
 
 60.0 
 37.8 
 32.1 
 35.9 
 
 37.1 
 
 15.0 
 53.4 
 45.3 
 49.5 
 
 35.6 
 
 2.5 
 3.3 
 14.3 
 3.4 
 
 10.9 
 
 11 X 14 ... 
 
 11 X 13 
 
 11 X 55 
 
 Open- pollinated 
 check 
 
 
 Not classified because of irregularity due to poor pollination. 
 
 b These are not the total ear lengths, but are the actual number of inches of kernels on the cobs. 
 
 DESCRIPTION OF INBRED LINES 
 
 The Illinois Country Gentleman and Illinois Narrow Grain Ever- 
 green inbred lines that have been released by the Illinois Station for 
 commercial production are described in the following sections. The 
 descriptions apply to the inbred lines themselves, not to the crosses in 
 which the inbreds are used as parents. In this respect these descrip- 
 tions differ from those in the preceding discussion, in which the 
 inbreds were evaluated according to their performance in crosses. 
 
 Illinois Country Gentleman Inbred 1 
 
 Relation to Other Inbreds. Remotely related to Inbred 15, and 
 should therefore not be crossed with it. 
 
 Homozygosity. Uniform, inbred for seventeen generations. 
 
 Plant Characters. Height 5 to 6 feet, depending on soil and season ; 
 relatively few leaves and suckers ; leaves wider than usual. Two-eared, 
 vigorous, little or no lodging, good stalk (Fig. 2). Tassels large but 
 very apt to blast in hot weather. Color of silk, sun-red. a 
 
 "A "sun" color is one which is brought out only when the silk is exposed 
 to sunlight. 
 
1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 327 
 
 Ear Characters. Large, cylindrical, thick ears and long slender 
 kernels, both of which characters are dominant in single crosses 
 (Tables 11 and 13). Traces of rowing; tendency toward oval shape 
 of cobs (Fig. 3). In some years kernel pericarps tend to split, owing to 
 their tenderness. Canning quality of crosses is good. 
 
 Use in Crosses. In spite of poor tassels, Inbred 1 should ordi- 
 narily be used as the male parent in a cross, except in combination with 
 Inbreds 6 and 10, which should not be used as seed parents. It so hap- 
 
 FIG. 2. ILLINOIS COUNTRY GENTLEMAN INBRED 1 
 
 pens, however, that the best combinations of Inbred 1 are with Inbreds 
 6 and 10. For several years the Cross 1X6 gave excellent yields in 
 commercial use, but in recent years Inbred 1 seems to have developed 
 a tendency toward poor germination, and good field stands are con- 
 sequently hard to get. This may be an unidentified genetic character, 
 as there apparently was no unusual amount of rot or mold in the seed. 
 Inbred 1 has therefore been withdrawn from commercial production, 
 for the present at least. 
 
328 
 
 BULLETIN No. 466 
 
 \_May, 
 
 
 ' ' 
 
 FIG. 3. ILLINOIS COUNTRY GENTLEMAN INBREDS 1 AND 10, AND CROSS 1 X 10 (at right) 
 Inbred 1 was the seed parent and Inbred 10 the pollen parent. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 329 
 
 Inbred 1 produces high-yielding crosses having a high recovery 
 (Table 15). The ears of the crosses are large (Table 13), the quality 
 good (Table 11), the maturity about the same as that of open-polli- 
 nated strains (Table 12), and the amount of smut is slight (Table 14). 
 
 Inbred 1 is the only one of these inbreds which gives a fairly good 
 top cross (Table 5). 
 
 Best Crosses. 1X6 Tall, vigorous, with medium-large, good 
 Country-Gentleman-type ears. One ear out of sixteen is slightly rowed. 
 Kernels long and slender, cobs slightly oval, canning quality extra 
 fancy, yield good. Removed from commercial production pending 
 improvements in Inbred 1. 
 
 1 X 10 Tall and vigorous, resembling Cross '1 X 6 in ear type 
 (Fig. 3) but having longer kernels, no traces of rowing, and much 
 better type of ear. An outstanding type, giving high yields. Canning 
 quality fancy. Removed from commercial production pending improve- 
 ment in Inbred 1. 
 
 Illinois Country Gentleman Inbred 3 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Inbred for fifteen generations but still shows con- 
 siderable variation in type. Some of these variants have been isolated 
 and will breed true, but there is no evidence that they are superior 
 to the parent line. In fact most of them seem to be inferior. When 
 this inbred was grown in Idaho after twelve generations of inbreeding 
 in Illinois, the variations were very pronounced. Whether this line is 
 segregating, mutating, or simply fluctuating is not clear. However, 
 the variations apparently do not detract from the value of the line. 
 
 Plant Characters. Vigorous, tall on good soil in Illinois more than 
 6 feet tall. In Idaho, looks like open-pollinated Country Gentleman 
 and yields as well or better. Tassels large, same amount of suckering 
 as on open-pollinated strains. Tends to be leafy (Fig. 4). Medium 
 to medium-long shanks; long, loose husks, sun-red silks. 
 
 Ear Characters. Large, slightly tapered ears and long, fairly slender 
 kernels characters which are dominant in crosses. Slight traces of 
 rowing ; cob slightly oval ( Fig. 5 ) . 
 
 Use in Crosses. Should be used as female parent. Crosses give 
 fair yield and recovery (Table 5), husked ears the same size as open- 
 pollinated strains (Table 13) but maturity slightly earlier (Table 12). 
 Canning quality good. Smut damage generally slight (Table 14). 
 
 Because Inbred 3 has fair-sized kernels, the best cross combinations 
 of it are with Inbreds 6 and 10. 
 
330 
 
 BULLETIN No. 466 
 
 [May, 
 
 Best Crosses. 3X6 Tall, vigorous ; good Country-Gentleman-type 
 ears having long slender kernels (Fig. 5). Canning quality fancy. In 
 commercial production to a limited extent, but not used in Illinois. 
 
 3X8 Tall, vigorous ; tassels droopy ; ears long, somewhat 
 slender ; kernels medium length, fairly slender ; cobs slightly oval. Ear 
 type not as good as some other crosses. Yield good; canning quality 
 
 FIG. 4. ILLINOIS COUNTRY GENTLEMAN INBRED 3 
 
 fancy. In commercial production until 1938 but was not popular owing 
 to relatively large size of kernels. 
 
 3 X 10 Tall, vigorous; ears large and cylindrical; kernels long 
 and slender; canning quality fancy. Exceptionally good ear type, 
 resembling Cross 3x6. Not so resistant to drouth as Cross 3X6. 
 Has been in commercial production. 
 
1940-} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 331 
 
 24 26 26 27 28 29 8081 32 38 84 86 
 
 Z I I I > 6 8 ,'. 9 tt'T" ,*. , .it , \t , .11. 1 
 
 FIG. 5. ILLINOIS COUNTRY GENTLEMAN INBREDS 3 AND 6, AND CROSS 3X6 (at right) 
 Inbred 3 was the seed parent and Inbred 6 the pollen parent. 
 
332 
 
 BULLETIN No. 466 
 
 [May, 
 
 Illinois Country Gentleman Inbred 5 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Most variable of all the eight Country Gentleman 
 inbred lines released for production. Resembles Inbred 3 but shows 
 much greater variation in character. Has been inbred for fifteen 
 generations. Numerous widely diverse selections, many of which breed 
 true, have been isolated, but thus far none of these (Table 4) seems to 
 be consistently superior to the parent line. When grown in Idaho, 
 
 FIG. 6. ILLINOIS COUNTRY GENTLEMAN INBRED 5 
 
 variability increases, as is true also of Inbred 3, and seed produc- 
 tion there equals or exceeds that of open-pollinated Country Gentle- 
 man. The variations do not seem to detract from the value of the line. 
 Crosses are uniform. 
 
 Plant Characters. Tall, vigorous plants, growing 6 feet or more 
 high on good soil in Illinois. Stalks strong, usually two-eared; rela- 
 tively few leaves and few suckers ( Fig. 6) . Tassels have shown a con- 
 sistent tendency to blast in hot weather, but in the last few years 
 
1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 333 
 
 FIG. 7. ILLINOIS COUNTRY GENTLEMAN INBREDS 5 AND 10, AND CROSS 5 X 10 (at right) 
 Inbred 5 was the seed parent and Inbred 10 the pollen parent. 
 
334 BULLETIN No. 466 [May, 
 
 very rigid selection has improved the line considerably in this respect. 
 This blasting seems to be a recessive character, as it does not appear 
 in crosses. Tassels are good enough to propagate the line. Silks 
 sun-red. 
 
 Ear Characters. Unusually large ears, free from rots and molds. 
 Kernels finely wrinkled, of medium length and width (Fig. 7). Has a 
 tendency to row; and pericarps occasionally split. 
 
 Use in Crosses. Should be used as female parent. Crosses generally 
 have fairly high yields of unhusked ears (Table 15), a fair husking 
 percentage, but only moderate recovery of cut corn. Husked ears large 
 (Table 13) ; maturity about the same as that of open-pollinated strains 
 (Table 12) ; canning quality good in general; smut slight (Table 14). 
 Having large kernels, this inbred must be paired with lines having 
 small slender kernels, such as Inbreds 6 and 10. Since the tassel is 
 poor, the pollinator must have a vigorous tassel. 
 
 Best Crosses. 5X6 Tall and vigorous ; ears large, thick, cylin- 
 drical; kernels long, slender, finely wrinkled (when dry). Good yields; 
 canning quality fancy. In commercial production to a limited extent. 
 
 5 X 10 Tall and vigorous, producing a heavy yield of fodder; 
 ears very similar to Cross 5x6. Usually six to twelve inches taller 
 than Cross 5X6. Canning quality fancy. In yield tests Crosses 5x6 
 and 5 X 10 yielded the same, but there was some indication that Cross 
 5 X 10 resists drouth better. In commercial production (Fig. 7), and 
 has proved to be second only to Cross 8 X 6 in popularity. 
 
 Illinois Country Gentleman Inbred 6 
 
 Relation to Other Inbreds. Previous to the sixth parental genera- 
 tion Inbreds 6 and 10 had a common parent. 
 
 Homosygosity. Inbred for seventeen generations ; now fairly uni- 
 form. Minor variations in plant type occur, but these do not seem to 
 be hereditary. Ear characters are well fixed. 
 
 Plant Characters. Tall, vigorous ; few suckers ; relatively few leaves 
 (Fig. 8) ; mostly two-eared; silks sun-red. Height 6 feet or more on 
 good soil in Illinois. Tassels good. Leaves in some seasons are yellow- 
 ish green with small yellowish specks. Has considerable amount of 
 smut both on ears and on plants. 
 
 Ear Characters. Ears large, symmetrical, completely zigzag ; kernels 
 long and very slender; cobs slightly oval (Figs. 5, 9, and 18). These 
 characters are dominant. The single crosses have excellent ear type. 
 
 Use in Crosses. Most useful of the Country Gentleman inbreds. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 335 
 
 Being characterized by a symmetrical ear with long, unusually slender 
 kernels, and good quality, it has the ability to reproduce these charac- 
 ters in the cross. Therefore, any recommended cross in which Inbred 6 
 is used, has excellent ear type. The crosses have high yields, and a 
 high recovery of prime husked ears and cut kernels (Table 15). Ears 
 of the crosses are large (Table 13) ; maturity slightly earlier than 
 open-pollinated strains (Table 12) ; canning quality high (Table 15). 
 Tendency toward split pericarps in the crosses. Since it is susceptible to 
 smut (Table 14), it must be paired with lines that are relatively re- 
 
 FIG. 8. ILLINOIS COUNTRY GENTLEMAN INBRED 6 
 
 sistant to smut, such as Inbreds 1, 3, 5, and 8. Owing to the small 
 size of the kernels and smut susceptibility, Inbred 6 should not be used 
 as the seed parent in a cross. 
 
 Best Crosses. 1X6, 3X6, and 5x6 Previously described 
 under Inbreds 1, 3, and 5. 
 
 8X6 Vigorous ; slightly shorter than open-pollinated Country 
 Gentleman; relatively few suckers. Ears slightly tapering, good 
 Country Gentleman type (Fig. 9) ; kernels long and fairly slender. 
 
336 
 
 BULLETIN* No. 466 
 
 [May, 
 
 FIG. 9. ILLINOIS COUNTRY GENTLEMAN INBREDS 8 AND 6, AND CROSS 8X6 (at right) 
 Inbred 8 was the seed parent and Inbred 6 the pollen parent. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 337 
 
 Canning quality consistently fancy. Tassels droopy and thus well pro- 
 tected from the sun ; has never been known to fail to produce plenty of 
 pollen. Droopy tassels cause irregularities in height of plant, which 
 give the impression that this cross lacks uniformity in comparison with 
 other crosses. Actually very uniform in all respects except height. 
 Only segregation noted is with reference to tassel ears, a very small 
 percentage of which appear each year. 
 
 This cross (8 X 6), now in production on a large scale, is more 
 widely used than any of the other Country Gentleman crosses dis- 
 cussed here. It seems to have a relatively wide adaptation in the 
 Middle West. Its production is somewhat deceptive: The yields of 
 unhusked ears may not exceed those of open-pollinated Country 
 Gentleman (Table 1), but the percentage of recovery is very high 
 (Table 1) and the yields of cut kernels or of cases of corn per acre 
 are higher than those of open-pollinated strains. In tests by Neal 12 * 
 in Wisconsin, Cross 8X6 produced as much as 41.9 cases per ton, 
 compared with 24.1 cases of open-pollinated Country Gentleman, total 
 production being, respectively, 125.3 and 89.5 cases per acre. Yields 
 of unhusked corn were, however, 3.71 tons per acre of open-pollinated 
 Country Gentleman and only 3.30 tons of Cross 8X6. High recovery 
 such as this is very desirable from the canners' viewpoint, as the 
 value of the raw product per gross ton is much higher. 
 
 Illinois Country Gentleman Inbred 8 
 Relation to Other Inbreds. Closely related to Inbred 9. 
 Homozygosity. Inbred for seventeen generations; most uniform of 
 all the inbreds described in this publication. A number of true-breeding 
 plant variants have been isolated, but few of these have given any 
 better results than the original line (Table 4). Ear characters show 
 very little variation. 
 
 Plant Characters. Highly characteristic features quite different 
 from any other sweet corn now in production (Fig. 10). Vigorous; 
 considerable foliage ; suckers freely. Leaves dark green ; silks green. 
 Growth is normal but somewhat bushy up to the time of tasseling. 
 Not very susceptible to smut ; some smut usually appears on the tassels 
 but very little on the ears. Tassel unusually large and drooping, pro- 
 ducing plentiful amounts of pollen and not straightening until pollen is 
 actually shedding. The tassel is thus completely protected from the 
 sun, so that even in the severest heat and drouth there is no injury to 
 the anthers. This very desirable character is dominant in all crosses in 
 which Inbred 8 is used as a parent. 
 
338 
 
 BULLETIN No. 466 
 
 [May, 
 
 The drooping of the tassels seems to be due to abnormal growth 
 of the stalk evident in the forming of short internodes above the shoot 
 but normal ones below. Apparently the length of the internodes above 
 the shoots depends somewhat upon the stage of development reached 
 when the tassels straighten up, some straightening later than others. 
 This has the effect of varying the height and preventing the uniform 
 appearance at maturity which is generally characteristic of inbred lines. 
 
 Maturity is slightly later than that of any other of the inbreds 
 except Inbred 9. It is desirable, therefore, to plant Inbred 8 five to 
 
 FIG. 10. ILLINOIS COUNTRY GENTLEMAN INBRED 8 
 
 seven days before planting the pollen parent, tho ordinarily in Illinois 
 it does not develop too late if planted at the same time as the pollen 
 parent. In Idaho a fourteen-day spread in planting is necessary. 
 
 Inbred 8 shows a slight amount of segregation for tassel ears. 
 When it is grown in Idaho, rudimentary tassels appear at the end of 
 75 percent of the cobs, but selections free from this character have 
 been made. In the Middle West and in the East cob tassels do not 
 appear in any of the strains of Inbred 8. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 339 
 
 Ear Characters. Very long and slender but heavy in weight (Fig. 9). 
 Kernels large in diameter but short. These ear characters limit the use 
 of Inbred 8 in crosses, as the other parent must have long slender 
 kernels and a rather thick ear. Seed quality, however, is excellent. 
 
 Use in Crosses. Should be used as the seed parent in crosses, but 
 owing to the droopy tassel the operation of detasseling is somewhat 
 more difficult than in inbreds not having this character. Superior in 
 crosses to Inbred 9 (to which it is closely related), despite the fact that 
 in general vigor and appearance Inbred 9 is the better-looking line. 
 Crosses involving Inbred 8 generally produce good yields of all three 
 yield components: unhusked ears, prime husked ears, and cut kernels 
 (Tables 10 and 15). In compatible crosses the husked ears are the 
 same size as those of open-pollinated strains (Table 13), and ma- 
 turity also is the same (Table 12). Canning quality is good. Only 
 a slight amount of smut appears in the crosses, as Inbred 8 is rela- 
 tively resistant to smut (Table 14). 
 
 Best Crosses. 3X8 Described under Inbred 3. 
 
 8X6 Described under Inbred 6. 
 
 8X10 Very similar to Cross 8X6 but taller and more vigorous. 
 Yields good (Table 5) ; ears equal to those of Cross 8X6. This 
 cross has not entered commercial production, because it is not quite 
 so productive as Cross 8x6, as shown by extensive tests in 1939 of 
 crosses made with several strains of Inbreds 8 and 10. 
 
 Illinois Country Gentleman Inbred 9 
 
 Inbred 9 is closely related to Inbred 8, has exactly the same physical 
 characters, but when the two are placed side by side Inbred 9 is superior 
 in all respects. However, Inbred 8 produces uniformly superior 
 crosses, and for that reason Inbred 9 has been withdrawn from com- 
 mercial production. 
 
 Illinois Country Gentleman Inbred 10 
 Relation to Other Inbreds. Closely related to Inbred 6. 
 Homozygosity. Inbred for seventeen generations; now fairly uni- 
 form tho slightly different plant types which breed true can still be 
 isolated. A green-silk, yellow-anther type was isolated in 1937. Ear 
 characters, however, are well fixed. 
 
 Plant Characters. Resembles Inbred 6 rather closely except that 
 it is more vigorous and slightly taller (Fig. 11) and does not have 
 speckled leaves. Less susceptible to smut than Inbred 6. 
 
340 
 
 BULLETIN No. 466 
 
 [May, 
 
 Ear Characters. Very similar to Inbred 6 except that kernels are 
 slightly larger and ears usually larger (Figs. 3, 7, 12, and 19). 
 
 Use in Crosses. Altho Inbreds 6 and 10 are closely related and 
 quite similar in appearance, they are not interchangeable in crosses. 
 In crosses Inbred 10 is comparable to Inbred 6 in giving high yield and 
 high recovery (Table 15). The ears in compatible crosses are large 
 (Table 13), and maturity is slightly earlier (Table 12) than in open- 
 pollinated strains. Canning quality is equal to that of Inbred 6. In 
 
 FIG. 11. ILLINOIS COUNTRY GENTLEMAN INBRED 10 
 
 spite of Inbred 10 being less susceptible to smut than Inbred 6 the 
 crosses on the whole have as much smut as Inbred 6 (Table 14). In 
 the best combinations, however, Inbred 10 gives plants having larger 
 ears and less smut than those given by Inbred 6. Owing to its small 
 kernels Inbred 10 should be used as the pollen parent. 
 
 Best Crosses. 3X10 Described under Inbred 3. 
 
 5 X 10 Described under Inbred 5. 
 
 8 X 10 Described under Inbred 8. 
 
ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 341 
 
 FIG. 12. ILLINOIS COUNTRY GENTLEMAN INBREDS 10 AND 15, 
 
 AND CROSS 10 X 15 (at right) 
 Inbred 10 was the seed parent and Inbred 15 the pollen parent. 
 
342 
 
 BULLETIN No. 466 
 
 [May, 
 
 Illinois Country Gentleman Inbred 15 
 
 Relation to Other Inbreds. Remotely related to Inbred 1. 
 
 Homozygosity. Inbred for fifteen generations ; fairly uniform for 
 plant characters ; little variation in ear characters. Several generations 
 of growth in Idaho have produced a number of quite different segre- 
 gates which may eventually prove to be superior. 
 
 Plant Characters. Tall (5 to 6 feet) ; leaves yellowish, mottled, 
 subject to dying-back more or less, even in favorable growing seasons 
 (Fig. 13). Dying-back of the leaves does not seem to be associated 
 
 FIG. 13. ILLINOIS COUNTRY GENTLEMAN INBRED 15 
 
 with any disease. Maturity, among the earliest of the inbreds. Subject 
 to tassel-blasting in hot dry weather, but has been improved in this 
 respect in recent years. Tassels and stalk susceptible to smut. 
 
 Ear Characters. Ears medium-sized, somewhat slender; kernels 
 relatively short and broad, dark in color, finely wrinkled, and fre- 
 quently have the silks adhering to them (Fig. 12). Pericarps split 
 in some seasons. Slight traces of rowing, probably due to the fact 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 343 
 
 that some of the kernels are almost always aborted. Ears relatively free 
 from rots and molds. 
 
 Use in Crosses. Owing to its low seed production Inbred 15 should 
 be used as the pollen parent in crosses. Crosses have low yields of 
 unhusked ears (Tables 8 and 15) but very high recovery (Table 10), 
 thus producing corn which has a high tonnage value and heavy pro- 
 duction of cases per acre. Husked ears of crosses are large (Table 13). 
 Maturity about the same as that of open-pollinated strains (Table 12). 
 
 Tho Inbred 15 has a number of undesirable characters, many of 
 the crosses in which it has been used have given excellent yields of 
 corn having unusually good canning quality (Tables 5 and 15). The 
 canned kernels are white (Table 11). 
 
 Inbred 15 has been in limited production only. None of the crosses 
 are available commercially. 
 
 Best Crosses. 8X 15 Long, somewhat slender ears with long 
 slender kernels. Some ears have slight traces of kernel-rowing. Yields 
 good ; canning quality good. 
 
 10X15 and 6x15 Medium-sized, somewhat thick ears with 
 very long slender kernels. Canning quality exceptionally good and 
 yields also good. 
 
 Illinois Narrow Grain Evergreen Inbred 11 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Inbred for seventeen generations but has tended to 
 be somewhat unstable, segregating several times, the last in P 12 . This 
 lack of stability in the inbred, however, seems not to affect the types or 
 yields of the crosses. 
 
 Plant Characters. Very tall, averaging 6 to 7 feet in Illinois. Rela- 
 tively leafy, few suckers, tassels erect and surrounded by erect leaves. 
 Well-eared, shanks medium length, flag leaves few, husk coverage only 
 average. Does not have much smut. 
 
 Ear Characters. Good seed-producer; rowing irregular, 18 to 22 
 rows ; ears long ; kernels somewhat slender, medium in length and 
 width, and having some split pericarps (Fig. 14). 
 
 Use in Crosses. Has given some trouble with tassel-blasting in hot 
 weather, but the selections released to seedsmen in 1939 seem to have 
 much better tassels. Should be used as the seed parent until tassels 
 have been proven by experience not to blast in hot weather. 
 
 Best Crosses. 11x13 (13X11) Unusually large, somewhat 
 tapering ears 8 to 9 inches long; eighteen to twenty rows, practically 
 
344 
 
 BULLETIN No. 466 
 
 [May, 
 
 FIG. 14. ILLINOIS NARROW GRAIN EVERGREEN INBREDS 11 AND 13, AND CROSS 11 X 13 
 Inbred 11 was the seed parent and Inbred 13 was the pollen parent. 
 
 no ears having fewer than eighteen rows. Kernels long and slender ; 
 canning quality excellent. Plants unusually tall, varying from 8 to 9 
 feet, which averages about 1 foot taller than open-pollinated Narrow 
 Grain Evergreen. Suckers few ; practically no lodging. An unusually 
 desirable type because of its large ears and slender kernels. 
 
 11 X 14 (14 X 11) See under Inbred 14. 
 
 11X55(55X11) Very large, symmetrical, straight-rowed ears 
 7 to 9 inches long ; eighteen to twenty-two rows, practically no ears 
 
1940] 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 345 
 
 having fewer than eighteen rows. Kernels long and slender; canning 
 quality excellent. Plants average 8 feet tall ; few suckers ; good husk 
 coverage ; shanks occasionally somewhat long ; practically no lodging. 
 Like Cross 11 X 13 this is an unusually desirable type because of 
 high-quality ears and long slender kernels (Fig. 20). 
 
 Illinois Narrow Grain Evergreen Inbred 13 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Inbred for seventeen generations ; has shown but 
 little variation in later generations. Repeated selections out of the 
 parent line do not deviate very much from the original. 
 
 FIG. 15. ILLINOIS NARROW GRAIN EVERGREEN INBRED 13 
 
 Plant Characters. Tall, vigorous, attaining a height of 6 feet or 
 more in Illinois under favorable conditions ; leaves numerous, dark 
 green, relatively narrow ; suckers rather freely ; large straggly tassels 
 not subject to blasting in hot weather (Fig. 15). Sun-red silks and 
 long husks. In maturity this line is slightly later than Inbred 14. 
 
346 
 
 BULLETIN No. 466 
 
 -N. 
 
 \_May, 
 
 FIG. 16. ILLINOIS NARROW GRAIN EVERGREEN INBR 
 
 CROSS 14 X 13 (at right) 
 Inbred 14 was the seed parent and Inbred 13 was the pollen parent. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 347 
 
 Ear Characters. Large tapering ears, large butts, fourteen to six- 
 teen rows, rowing irregular, kernels long, medium width (Fig. 16). 
 
 Use in Crosses. Owing to its excellent tassel characters and 
 slightly later maturity than is exhibited by many inbreds, Inbred 13 
 should be used as a male in crosses. 
 
 Best Crosses. So far the best combinations seem to be Cross 
 14 X 13 (Fig. 16) and Cross 11 X 13 (Fig. 14). Crosses with Country 
 Gentleman Inbreds 6 and 10 give high yields but the ears tend to be 
 long and slender, with very indistinct rowing. 
 
 Illinois Narrow Grain Evergreen Inbred 14 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Inbred for seventeen generations ; has shown but 
 little variation in the last eight years altho repeated selections have 
 been made. "Prepotent" or "dominant" in the sense that it is prac- 
 tically always possible to recognize easily any cross in which it is used. 
 
 Plant Characters. Very tall, averaging 7 feet in Illinois ; leaves 
 few and relatively narrow ; suckers few ; tassels relatively small, with 
 few branches (Fig. 17). Well-eared; shanks medium to medium- 
 long; husks long; flag leaves few; silks sun-red. Tassel seeds on 
 suckers, but seldom on main stalks. Susceptible to smut in the tassels 
 and to some extent on the stalks, but relatively little on the ears. 
 
 Ear Characters. Ears relatively large, with twelve to sixteen rows 
 (Figs. 16, 18, and 19) ; unusually bright and clean, with translucent 
 kernels. Kernels medium in length and width, and finely wrinkled. 
 
 Use in Crosses. As Inbred 14 is a heavy seed-producer, it should 
 be used as the seed parent in crosses except possibly with Inbred 11. 
 Crosses well with many inbred lines. When combined with Country 
 Gentleman Inbreds 6 or 10, a good type of ear is assured. 
 
 Best Crosses. 14 X 6 Large, slightly tapering ears, sixteen to 
 eighteen rows slightly irregular and on occasional ears quite irregular 
 (Fig. 18). Kernels medium in width and length. Canning quality 
 excellent, yield high. Distinctly a Narrow Grain Evergreen type and 
 cannot be substituted for Country Gentleman. Plants are 8 feet tall, 
 slightly larger than open-pollinated Narrow Grain Evergreen. 
 
 14X10 Large, slightly tapering ears ; fourteen to eighteen rows, 
 resembling Cross 14X6 very closely both in ear and kernel type ( Fig. 
 19) and in plant type. Under some conditions Cross 14 X 10 gives 
 better yields and larger ears than Cross 14 X 6. Canning quality good. 
 
348 
 
 BULLETIN No. 466 
 
 [May, 
 
 14 X 13 Extremely large cylindrical ears ; fourteen to twenty-two 
 rows, practically straight (Fig. 16). Kernels long and medium-wide. 
 Height about 8 feet, slightly taller than open-pollinated Narrow Grain 
 Evergreen. Yields higher under most conditions than Cross 14 X 6 or 
 Cross 14 X 10, but the canning quality is not quite so good. Superior 
 in quality, however, to open-pollinated Narrow Grain Evergreen. 
 
 FIG. 17. ILLINOIS NARROW GRAIN EVERGREEN INBRED 14 
 
 14 X 11 (11 X 14) Best direction in which to make this cross 
 not definitely known, as it does not go into commercial production until 
 1940. Ears large and symmetrical; sixteen to twenty straight rows 
 (Fig. 20). Kernels long and slender. Height 8 to 9 feet; suckers few; 
 husks good ; very little lodging. Quality -of canned corn excellent, 
 superior to open-pollinated Narrow Grain Evergreen. 
 
 Illinois Narrow Grain Evergreen Inbred 55 
 
 Relation to Other Inbreds. None. 
 
 Homozygosity. Inbred for fifteen generations; has not changed in 
 appearance for many years. 
 
1940^ 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 349 
 
 FIG. 18. ILLINOIS NARROW GRAIN EVERGREEN INBRED 14 AND ILLINOIS COUNTRY 
 
 GENTLEMAN INBRED 6, AND CROSS 14 X 6 (at right) 
 Inbred 14 was the seed parent and Inbred 6 the pollen parent. 
 
350 
 
 BULLETIN No. 466 
 
 {.May, 
 
 ! 22 ' 213 2J4 26 28 27 28 29 80 ' 111 8*2 ' 8:8 : 8i4 
 
 FIG. 19. ILLINOIS NARROW GRAIN EVERGREEN INBRED 14 AND ILLINOIS COUNTRY 
 
 GENTLEMAN INBRED 10, AND CROSS 14 X 10 (at right) 
 Inbred 14 was the seed parent and Inbred 10 the pollen parent. 
 
1940} 
 
 ILLINOIS SWEET-CORN INBREDS AND CROSSES 
 
 351 
 
 FIG. 20. ILLINOIS NARROW GRAIN EVERGREEN INBREDS 55, 11, AND 14, AND 
 
 CROSSES 11 X 55 AND 11 X 14 
 
 Inbred 11 was the seed parent in both crosses, and Inbreds 55 and 14 were the pollen 
 parents. 
 
352 BULLETIN No. 466 [May, 
 
 Plant Characters. Very tall, averaging 7 to 8 feet ; unusually vigor- 
 ous. Stalks very sturdy ; suckers few ; tassels large and well protected, 
 free from blasting. Silks red. Shanks tend to be long. Lodging very 
 infrequent. Very little smut. 
 
 Ear Characters. Good seed-producer, with 1 to 2 ears per stalk. 
 The dry ears are large, unusually heavy, dark and dull looking. Four- 
 teen to eighteen rows, but rowing irregular (Fig. 20). Kernels medium 
 in length and width, packed very tightly on cobs ; shelling not easy. 
 
 Use in Crosses. May be used either as pollen or as seed parent. The 
 best combination seems to be with Inbred 11, with which it may be 
 used as either the seed parent or the pollen parent. 
 
 Best Crosses. 11 X 55 (55 X 11) Described under Inbred 11. 
 
 SUMMARY AND CONCLUSIONS 
 
 From sweet-corn breeding begun in 1922 at the Illinois Agricultural 
 Experiment Station a number of inbred lines and single crosses between 
 the inbred lines have been developed and released for commercial pro- 
 duction, and in addition light has been thrown on some of the prob- 
 lems involved in inbreeding, selection within inbred lines, and hybrid- 
 ization. The work reported in this bulletin has been done with the 
 Country Gentleman and Narrow Grain Evergreen varieties, but yellow 
 varieties have also been included in the program since 1930. Twelve 
 inbreds (eight of Country Gentleman and four of Narrow Grain 
 Evergreen) have been released at various times for commercial propa- 
 gation. Three of the Country Gentleman inbreds were withdrawn for 
 different reasons after being released. 
 
 The principal facts pertaining to these inbreds and their crosses, 
 and some of the more significant conclusions to be drawn from the 
 breeding w r ork, are the following: 
 
 Yields. From the standpoint of yields of sweet corn, the superior- 
 ity of good single crosses over good open-pollinated strains of the same 
 variety was chiefly a matter of (1) a decreased variation of yield from 
 year to year by the crosses, and (2) a significantly greater recovery 
 of prime cut kernels per ton of unhusked ears from the crosses. 
 
 During the six years 1931, 1933-1937, including three years of 
 severe drouth, the coefficient of variability in yield of the well-adapted 
 Cross 8X6 was 29.5 percent on the basis of tons of prime cut kernels 
 per acre, while that of the open-pollinated check was 45.1 percent. 
 During the same years the recovery of cut kernels per ton of un- 
 husked ears was 22.6 percent higher from the cross than from the 
 
1940} ILLINOIS SWEET-CORN INBREDS AND CROSSES 353 
 
 open-pollinated check. Such differences are typical, and because of their 
 existence the yield of sorted unhusked ears is not so reliable as the 
 yield of prime cut kernels as a basis for estimating the value of a 
 single cross. During the six years the cross produced 41.8 percent more 
 tons of prime cut kernels per acre than the check, but only 33.9 percent 
 more prime husked ears, and 18.6 percent more sorted unhusked ears. 
 
 Adaptability. Even after seventeen generations of inbreeding in 
 Illinois, when a high degree of homozygosity had presumably been 
 attained, the removal of the inbreds to the highly favorable seed-pro- 
 ducing regions of Idaho and Connecticut resulted ultimately in segrega- 
 tion, mutation, and general deterioration. In three-year tests the yields 
 of corn grown in Illinois from crosses of Illinois inbreds maintained 
 and crossed in Idaho ranged from 1.6 to 36.4 percent below the yields 
 of corn grown from crosses of Illinois inbreds maintained and crossed 
 in Illinois. Similar tests with Purdue 39 and Purdue 51 inbreds main- 
 tained and crossed for three successive years in Idaho showed that the 
 cross, Golden Cross Bantam, deteriorated very rapidly and progres- 
 sively in yield. On the basis of these and similar trials the more pro- 
 gressive seedsmen are now maintaining their inbreds in the Middle 
 West and merely making the crosses in Idaho. Whether or not this 
 method will prove satisfactory is still uncertain. 
 
 As to the adaptability of crosses to different regions, the data 
 available are too limited to give a conclusive answer, but it is believed 
 that a successful single cross must have a more than local range. 
 Crosses restricted in range may also prove to be equally restricted in 
 adaptability to variations in local weather conditions. 
 
 Effect of Continued Selection Within Inbreds. Not much progress 
 could be made toward improving crosses by means of selections within 
 the inbred parents on the basis of physical characters. 
 
 Selection on this basis proved to be more promising, however, in 
 unstable than in stable lines. When selections of any kind are made, the 
 only known basis for determining their value is to cross and to check 
 the cross for the desired characters. 
 
 Selective Use in Crosses. On the basis of numerous yield tests 
 the various inbreds were classified as to their best use in crosses that 
 is, whether as pollen parent or as seed parent. When their selectivity 
 in this respect was determined, the crosses could then be classified as 
 compatible, incompatible, and antagonistic. 
 
 Of these three kinds of crosses the compatible crosses were usually 
 superior to the incompatible and antagonistic crosses. Some of the 
 
354 BULLETIN No. 466 [Mav, 
 
 differences were due to physiological causes, such as size of seed or 
 susceptibility to seed-borne diseases, but there was a residue apparently 
 due to unknown genetic causes. 
 
 Bases for Evaluation of Inbreds. The inbred lines were evaluated 
 first on the bases of appearance, quality, and yields ; then when a fair 
 degree of uniformity in these respects had been attained, they were 
 further evaluated by measuring their performance in crosses. By 
 averaging the yields and other measures of performance of a series 
 of reciprocal crosses, the selectivity of the parents and their desirable 
 characters and defects could be determined an important point since 
 the heredity of the quantitative characters is unknown. 
 
 Quality as well as yield seemed to be definitely associated with 
 inbred lines, inasmuch as given quality characters ran thru, a series 
 of crosses in which the same parent had been used, indicating that 
 hereditary characters were involved. Altho none of the twelve released 
 inbreds were consistently poor in quality, a fact which was to be ex- 
 pected inasmuch as they had been selected as the most promising 
 out of more than one hundred lines, some differences did, nevertheless, 
 exist. Inbred 4, for instance, was outstanding in the quality of its 
 crosses, particularly in their flavor. 
 
 In maturity most of the crosses were slightly earlier than the open- 
 pollinated checks. Some of the inbreds, however, produced later- 
 maturing crosses than others. Size of seed had an effect on maturity. 
 The small-seeded Inbred 6, when used as seed parent, produced crosses 
 maturing definitely later than the crosses produced when it was used 
 as pollen parent. 
 
 The inbreds showed considerable variation in weight per husked 
 ear. Some lines had consistently lighter-weight ears than others, 
 indicating that this quantitative character is probably hereditary. 
 
 A similar variation in incidence of smut on the ears was observed. 
 The crosses of some inbred lines had, on the average, very little smut 
 on the ears ; those of other lines had much more. 
 
 Best Crosses. Because of superior canning quality, wide adapta- 
 bility, high yields of prime cut kernels, and' resistance to drouth, smut, 
 and tassel-blasting, the two Country Gentleman Crosses 8X6 and 
 5 X 10 have proved to be the most popular of all the crosses of the 
 inbreds released by this Station. Of these two, Cross 8X6 has been 
 much more popular than Cross 5 X 10. Numerous tests by other 
 stations and by growers and canners have demonstrated that these two 
 crosses may be grown successfully wherever open-pollinated Country 
 Gentleman strains succeed. 
 
1940] ILLINOIS SWEET-CORN INBREDS AND CROSSES 355 
 
 Of the Narrow Grain Evergreen crosses, Cross 14 X 13, available 
 since 1937, has been the most popular, tho it has been much less widely 
 grown in Illinois than the Country Gentleman crosses. Probably one 
 or more of the new group of Narrow Grain Evergreen crosses released 
 for 1940, crosses between Inbreds 11 and 13, 11 and 14, and 11 and 55, 
 will find a wide use. Because of more economical production when 
 several crosses can be made using one inbred as the male parent for 
 all, these crosses will probably be marketed as Crosses 13 X 11, 
 14XH, and 55 X H- More widely adaptable than the Country 
 Gentleman crosses, these crosses can be grown successfully wherever 
 open-pollinated Narrow Grain Evergreen strains succeed. 
 
 LITERATURE CITED 
 
 1. ASHBY, E. Studies in the inheritance of physiological characters: I. A 
 
 physiological investigation of the nature of hybrid vigor ih maize. Ann. 
 Bot. [London] 44, 457-470. 1930. 
 
 2. Studies in the inheritance of physiological characters: II. 
 
 Further experiments upon the basis of hybrid vigor and upon the in- 
 heritance of efficiency index and respiration rate in maize. Ann. Bot. 
 [London] 46, 1007-1032. 1932. 
 
 3. BURGESS, R. W. Introduction to the mathematics of statistics, p. 262. Boston. 
 
 1927. 
 
 4. DUNCAN, G. H., HOLBERT, J. R., MUMM, W. J., BIGGER, J. H., and LANG, A. C. 
 
 Illinois corn performance tests (results for 1935). Ill Agr. Exp. Sta. Bui. 
 427. 1936. 
 
 5. EAST, E. M. Inbreeding in corn. Conn. Agr. Exp. Sta. 31st Ann. Rpt. (1907) 
 
 pp. 419-428. 1908. 
 
 6. FISHER, R. A. Statistical methods for research workers. London, 1932. 
 
 7. HOPKINS, C. G. Improvement in the chemical composition of the corn kernel. 
 
 111. Agr. Exp. Sta. Bui. 55. 1899. 
 
 8. HUELSEN, W. A., and GILLIS, M. C. Inheritance of kernel arrangement in 
 
 sweet corn. 111. Agr. Exp. Sta. Bui. 320. 1929. 
 
 9. and MICHAELS, W. H. The yield complex of sweet corn. 111. 
 
 Agr. Exp. Sta. Bui. 432. 1937. 
 
 10. JONES, D. F. The effects of inbreeding and crossbreeding upon development. 
 
 Conn. Agr. Exp. Sta. Bui. 207. 1918. 
 
 11. - and HUNTINGTON, E. The adaptation of corn to climate. Amer. 
 
 Soc. Agron. Jour. 27, 261-270. 1935. 
 
 12. NEAL, N. P. Results of 1937 hybrid sweet corn trials in Wisconsin. Canner, 
 
 86, No. 23, pp. 14-16, and No. 24, pp. 18, 20, 22. 1938. 
 
 13. RICKEY, F. D. Corn breeding. U. S. Dept. Agr. Dept. Bui. 1489. 1927. 
 
 14. SHULL, G. H. The composition of a field of maize. Am. Breeders Assoc. 
 
 Rpt. 4, 296-301. 1908. 
 
 15. SMITH, G. M. Golden Cross Bantam sweet corn. U. S. Dept. Agr. Circ. 268. 
 
 1933. 
 
 16. SMITH, L. H. Ten generations of corn breeding. 111. Agr. Exp. Sta. Bui. 128. 
 
 1908. 
 
 17. SPRAGUE, G. F. Hybrid vigor and growth rates in a maize cross and its 
 
 reciprocal. Jour. Agr. Res. 53, 819-830. 1936. 
 
Policy Governing 
 Seed Distribution 
 
 Seed of the new sweet-corn inbreds and 
 crosses described in this bulletin is not avail- 
 able at the Illinois Agricultural Experiment 
 Station either for sale or for free distribu- 
 tion. Inbreds are available only to commer- 
 cial seedsmen who have the necessary equip- 
 ment and experience for maintaining them 
 and for properly producing the crosses, and 
 who sign an agreement with the Board of 
 Trustees of the University of Illinois to pro- 
 duce the crosses under Station supervision. 
 Seed of the crosses is available from these 
 commercial seedsmen. Write to the Illinois 
 Station for further information. 
 
 2,5505-4018671 
 
UNIVERSITY OF ILLINOIS-URBANA