ybraiy *v College Aqriculturt University of Illinois Library at Urbana-Champaign ACES ilS UNIVERSITY LIBRARY UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN The person charging this material is responsible for its zr? 1 ^: 6 ^. to i he "^ - - ^ journals. Theft mutilation, and underlining of books are reasons or d sc.pl.nary action and may result in dismissal from the Un.vers.ty. Please note: self-stick notes may est in torn pages and lift some inks. Jufi n 9fi9 V i^n^?l eph0ne Center at 21 7 -333-8400, o^o-^b^-1510 (toll-free) orcirclib@uiuc.edu Renew online by choosing the My Account option af http://www.library.uiuc.edu/catalog/ m UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN No. 132 THE EFFECT OF SELECTION UPON CERTAIN PHYSICAL CHARACTERS IN THE CORN PLANT BY LOUIE H. SMITH URBANA, ILLINOIS, FEBRUARY, 1909 SUMMARY OF BULLETIN No. 132 1. This bulletin reports the results of experiments in breeding corn to modify certain physical characters in the plant; namely, (1) Height of ear on stalk, and (2) Declination of ear from stalk. 2. By breeding a variety in opposite directions two strains of corn have been produced in one of which ears are now borne about three feet higher on the stalk than in the other strain. Page 53 3. Selecting simply "with reference to height of ear has induced some pro- nounced secondary effects upon the plant. The plants of the high-ear strain have longer stalks, longer internodes, a greater total number of internodes and a greater number of internodes below the ear than have those of the low-ear strain. Page 53 4. There is a noticeable difference in the length of growing period in the two strains, early maturity being associated with the smaller type of plant of the low-ear strain. Page 56 5. Comparative tests for yield thus far indicate no great difference between the two strains in production of grain but the high-ear strain produces the more fodder. Page 56 6. Experiments in selection for erect and declining ears indicate that the declining habit is a character which can be influenced by breeding. Page 58 7. No significant effect from this selection has yet been produced on the yield. Page 58 8. The length of shank appears to be the principal factor in determining the declining habit. Page 60 9. The practical advantages in the declining ear are found in the better protection from rain and the greater convenience in handling at harvest. Page 60 48 PLATK 1. REPRESENTATIVE STALKS TAKEN FROM THE HIGH-EAR AND LOW-EAR PLOTS IN THE FIFTH GK.NK.RATION. Acknowledgment is due and is hereby gratefully given to the following persons who have at various times been responsible for the conduct of the ex-, periments reported in tHis bulletin : Doctor E. M. East, now agronomist at the Connecticut Experiment Sta- tion; Mr. H. H. Love, now assistant in experimental plant-breeding at Cornell University and Mr. C. H. Myers, assistant. in chemistry at the Illinois Agri- cultural Experiment Station. 50 THE EFFECT OF SELECTION UPON CERTAIN PHYSICAL CHARACTERS IN THE CORN PLANT By LOUIE H. SMITH, Assistant Chief in Plant Breeding Among the various lines of investigation in corn breeding at this Station a series of experiments has been conducted for a number of years to test the possibility of modifying by continuous selection certain physical characters of the corn-plant. It is the purpose of this bulletin to report the results obtained in the experiments to influence two such characters; namely, the height at which the ear is borne upon the stalk, and the position of the ear with reference to its declination from the stalk at maturity. HIGH AND LOW EARS GENERAL PLAN OF THE EXPERIMENT In the autumn of 1902 from an ordinary field of Learning corn two sets of ears were selected, one of which represented ears growing high on the stalk and the other those borne low down on the stalk. These two sets of ears were planted the following spring in separate breeding plots, and selection for high ears and for low ears, from the respective plots, has been made each year since. As this experiment was undertaken in part for the purpose of demonstration, the two plots have always been planted end to end for the sake of convenient inspection altho it is recognized that such close proximity of different breeding plots may not represent ideal condi- tions for the best results on account of the danger of inter-crossing. This difficulty has however been practically eliminated by taking the precaution always to confine the selection of seed ears to plants located toward the outer ends of the plots. If perchance any such inter- crossing has occurred in these plots the remarkable progress which the results show has been made in spite of such a handicap. The plots are planted according to our regular ear-row system, and productiveness is made the basis of the first selection. Thus, only the best yielding plot-rows are selected and from these rows the seed ears are chosen with reference to the height at which they are borne upon the stalk, only good sound ears being taken. The number of ears planted in the breeding plot has varied in the different years but the plan now followed is to have 24 rows, 51 52 BULLETIN No. 132 [February, each row planted from an individual ear. Alternate rows are detas- seled and four seed ears are taken from each of the best six detasseled rows, arranging the order of planting the following year with refer- ence to the relationships of these seed ears so as to avoid as much as possible any close-breeding. THE DATA The data are obtained by taking the observations on the plants at certain intervals, every third hill, in each plot row, so that the yearly results given are derived from the averages of large numbers of observations, thus securing a very fair representation of the plots. These observations have included the following points: (1) the height of ear, (2) the total length of stalk above ground, (3) the node at which the ear is borne (counting from the ground upward), and (4) the total number of internodes of the stalk. SUMMARY OF THE RESULTS From the records of these observations the following table is constructed by bringing together the averages for each generation, placing the corresponding data of both plots side by side for con- venient comparison. Table No. 1. CORN BREEDING FOR HIGH EARS AND FOR Low EARS (General averages of crops produced in each of six generations) Year Height of ear (inches) Height of plant (inches) Number of inter- nodes below ear Total number in- ternodes of stalk High- ear plot Low- ear plot High- ear plot Low- ear plot High- ear plot Low- ear plot High- ear plot Low- ear plot 1903 56.4 50.3 63.3 56.6 72.4 57.3 42.8 38.3 41.6 25.5 33.2 23.1 113.9 106.2 128.4 116.3 130.4 114.0 102.5 97.4 106.5 86.0 99.7 79.3 8.5 7.5 8.2 9.0 9.2 8.2 1 7.2 6.2 6.5 5.9 5.8 4.7 15.4 14.5 15.4 15.1 16.3 15.5 13.9 13.0 13.6 11.0 13.0 11.5 1904 1905 1906 1907.. 1908 The growth is of course affected by environmental conditions as well as by hereditary tendencies and the absolute height of ear on the stalk as well as height of plant will be, so to speak, a resultant of these two factors, varying from year to year in accordance with soil and season. But by having the high-ear and low-ear plots grow- ing side by side each year we may eliminate to some extent at least the environmental factor and get a measure of the effect really due to heredity. A clearer view of the general progress of the breeding is obtained by observing the differences between the two plots in average height of ear, etc., for each year as derived from the preceding table. These differences are found to run as follows, 1909] EFFECT OF SELECTION ON PHYSICAL CHARACTERS IN CORN PLANT 53 Table No. 2. AVERAGE DIFFERENCES IN CROP EACH GENERATION RESULTING FROM SELECTION FOR HIGH EARS AND FOR Low EARS Year Difference in average height of ear (inches) Difference in average height of plant (inches) Difference in average number of inter nodes below ear Difference in average number of internodes of stalk 1903 13.6 11.4 1.3 * 1.5 1904 . . . v 12.0 8.8 1.3 1.5 1905 21.7 21.9 1.7 1.8 1906 31.1 30.3 3.1 4.1 1907 39.2 30.7 3.4 3.3 1908 34 2 34.7 3.5 4.0 These figures show in a striking manner the way in which the crop has responded to the seed selection. Thus we see in the second column of Table 2 that up to the last generation there has been in general a gradually increasing difference in height of ears in these two strains according to the breeding until this difference amounts to over three feet. It will be noticed that in the last generation instead of an advance as heretofore there appears to be a slight regression. This however may be accounted for in the fact that the season of 1908 was very unfavorable to corn in this locality, so that the large plants of the high-ear strain suffered more in their development from the adverse conditions than did those of the low-ear strain. Besides the direct effect upon the height of ear the data bring out clearly a very pro'nounced secondary effect produced by the selec- tion. Selecting the seed simply with reference to the height at which the ear is borne has resulted in an effect upon the height of the plant so that the stalks of the high-ear plot now average nearly three feet taller than those qf the low-ear plot. It is interesting to note that in this effect upon the height of ihe plant two factors have been involved, namely the number of inter- nodes and the average length of each internode. It is further evident from the data that these same two factors have been effective in determining the height of ear. That is to say, in selecting for high ears we have incidentally selected those plants having longer inter- nodes and bearing their ears at a higher node, while in the case of the low ears we have been selecting plants having shorter internodes and bearing their -ears at a lower node. Perhaps the most significant of all as throwing light upon broader problems of heredity is the fact brought out by these results that the corn has not only responded to the selection, but there has been a gradual progressive shifting of the types so that even in the fourth generation the average height of ears in the one strain is more than twice that in the other. Thus we find in its behavior in this regard a principle of breeding quite in accord to that observed in connection with the breeding of corn to modify the composition of the grain. (See bulletins 119 and 128.) 54 BULLETIN No. 132 {February, PLATE 2. IN THE HIGH-EAR PLOT AFTER FIVE YEARS OF BREEDING, 1909] EFFECT OF SF.LF.CTTON ON PHYSICAL CHARACTF,RS IN CORN PLANT 55 PLATE 3. IN THE LOW-EAR PLOT AFTER FIVE YEARS OF BREEDING. 56 BULLETIN No. 132 [February, We have in these results a striking illustration of the faithful manner in which corn responds to continuous systematic selection for a particular characteristic and an indication of the possibilities for the improvement of this all-important crop through judicious and persistent selection of the seed for definite purposes. EFFECT ON MATURITY Selection for high ears and low ears has resulted in a notable difference in the maturity of the two strains. This is especially apparent at the time of flowering. It was observed the last two seasons that the tassels were well developed in the low-ear plot before they appeared in the high-ear plot. The low-ear plot was apparently about a week in adyance of the high-ear plot at this stage. It is interesting to note in this connection that the same principle has been observed in regard to earliness in other crops. For example in breeding cotton where early maturity is desired in order to escape damage by the boll weevil it has been found that earliness is to be secured by .selecting plants of low growing habit with few and short internodes and with bolls borne low. Again in the case of the pea, the Swalof Plant-Breeding Station recommends, for earliness, to select such plants as possess but few internodes below the first flowers,, and the statement is made that the fewer the total number of internodes*the earlier is the ripening. As is well known our early varieties of corn are characterized by relatively small plants while those of late maturity usually have large plants with tall stalks requiring a longer growing season in which to complete the vegetative life. Thus our observations are quite in accord with what appears to be a general principle that applies not only to corn but also to other crops ; that is, early maturity is characterized by few and short inter- nodes with fruit borne low. One of the most important questions before the attention of corn growers and corn breeders at present is that of maturity. The demand is for grain that will grade better in the market, keep better in storage and transportation, and germinate better when planted in the field, and our problem is the difficult one of inducing earliness without sacrificing yield. EFFECT ON YIELD The question naturally follows as to how the yield has been affected by the selection for these two opposite characteristics. In the last three years seed has been carried from each of these breeding plots to our variety test plots, where conditions of soil and culture are made as uniform as possible for obtaining comparable yields. The results of this test given in terms of bushels of shelled corn per acre are as follows. 1909] EFFECT OF SELECTION ON PHYSICAL CHARACTERS IN CORN PLANT 57 Year High-ear strain Low-ear strain 1906 72.4 72.6 1907 64.5 68.8 1908 60.9 59.5 Thus we see that, in spite of the much smaller size of the low- ear plant, in production of grain this strain compares very favorably with the high ears. The evidence from a three-year trial of yields is rather too limited to warrant sweeping deductions, but the results cer- tainly indicate that by careful attention to the selection of good seed ears it is quite possible to maintain the rate of yield from the smaller, quicker maturing plant of the low-ear type. Some of our leading corn growers are advocating a reduction in the standard size of ear in the belief that a longer growing season is necessary for the production of the large type of ear that has been set for the ideal, and that striving to attain this ideal has resulted in lateness in maturity of some of our best varieties. This is to some extent plausible; but it would seem that the lesson brought out by these experiments is that attention should be given to size of plant as well as to size of ear and that by selecting well developed ears borne comparatively low on the stalk of smaller plants we shall accomplish more in inducing earliness at possibly less sacrifice in yield than in attempting to regulate the size of ear alone. ERECT AND DECLINING EARS Among the very noticeable variable characters to be seen in any field of mature corn is the manner in which the ear is borne with reference to the angle which it makes with the stalk. A few minutes observation will discover all degrees of declination of ears, varying from those which stand almost perfectly upright to those that hang straight downward. In order to determine to what extent this character might be in- fluenced by breeding and what value if any attaches to it, selection was begun in 1903 for "erect" and for "declining" ears. For this ex- periment two sets of ears were taken according to angle of declination at harvest time from our "Illinois High-Oil" breeding plot, a strain which had been under selection for seven generations for increase in oil content. These two sets of ears were planted in two corresponding breed- ing plots and selection has been kept up in these two directions since that time. The breeding plots have been conducted on the same general system as the "High-Ear" and "Low-Ear" plots just described, planting by the ear-row method, detasseling alternate rows and basing the first selection upon yielding capacity. THE DATA * Records have been taken each year by measuring the angle that the ear makes with the stalk on which it is borne just before the harvest. If the ear stands erect the angle is recorded as 0, if hori- 58 BULLETIN No. 132 [February, zontal it is 90 degrees, if hanging straight downward it is 180 degrees, and all intermediate positions are recorded in degrees corresponding. An index having a movable pointer and a half circle marked off in degrees has been found useful in taking these data. The measure- ments are taken when the corn is ripe at certain definite intervals in every row, so that the results obtained represent a fair average. From the records thus obtained the following averages have been taken which will serve to show very well the general progress of the work. Table 3. CORN BREEDING FOR ERECT EARS AND FOR DECLINING EARS (Degrees of declination from the perpendicular) Average of seed Average of crop Year Erect- Declining- Difference Erect- Declining- Difference ear ear between ear ear between strain strain strains strain strain strains 1904.. 20.0 180.0 160.0 42.0 45.0 3.0 1905.. 16.7 180.0 163.3 62.2 117.1 54.9 1906.. 15.0 180.0 165.0 49.5 76.2 26.7 1907.. 12.8 180.0 167.2 42.3 81.6 39.3 1908.. 7.2 176.0 168.8 46.0 88.5 42.5 It will be noticed that in the first generation the response to the selection was very slight as indicated by the results in the last column,, where the figures show the average difference each year between the two plots. In the second year this response was very much greater, in fact the results show that it was more marked that year than it has been since. The conditions of that season seem to have been excep- tionally favorable for declining ears as seen from the results in both plots. After the second year the average difference in the crops has steadily increased. On the whole we find that we have been able to influence this character to a considerable extent in the five years of breeding; and with the exception of 1905 it has responded almost as faithfully and regularly to selection as in the case of the -height of ear. EFFECT ON YIELD In regard to the influence of this selection upon the yield, it may be said that no decided effect is yet apparent. Following are the results of two years' trial in the variety test plots given in bushels of shelled corn per acre. 1 Year Erect-ear strain Declining-ear strain 1907 69.7 65.8 1908 60.2 62.2 DETERMINING FACTOR IN THE ANGLE OF DECLINATION The manner in which the erect or declining character is affected is of interest in this connection. 1909] EFFECT OF SELECTION ON PHYSICAL CHARACTERS IN CORN PLANT 59 PIRATE 4. AFTER FIVE GENERATIONS THE AVERAGE AMGLE OF DECLINATION IN THE ERECT-EAR STRAIN is 46. JN THE DECLINING EAR STRAIN IT is 88.5 60 BULLETIN No. 132 [February, In order to obtain some definite information on this matter a detailed study was made upon the crop of 1907 and it was found by measuring large numbers of specimens from both plots that the ear- branch or shank was on the average almost twice as long in the declining-ear strain as in the erect-ear strain, the averages for that year being about 12 inches and 7 inches respectively. The difference found in diameter of shank was so slight as to be insignificant. This indicates that in producing the declining ear we have really been selecting those plants which have longer shanks. In this study a count was made of the number of internodes of the shank and also of the number of husks. As might be expected the longer shanks of the declining ears had an average of a slightly larger number of internodes and correspondingly a larger average number of husks. PRACTICAL CONSIDERATION Most corn growers are of the belief that, in general, declining ears are preferable, especially in a wet autumn, on account of the better protection from rain and the consequent liability to decay. As a matter of fact it has been noticed for a number of years that there has been more unsound corn in the erect-ear plot than in the declining- ear plot. In 1908 a count was taken of the number of mouldy or rotted ears in each plot, and the records show 5.33 percent of the unsound ears in the erect-ear plot and only 2.05 percent in the de- clining-ear plot. It should be considered in this connection that this was an exceptionally dry autumn. In some seasons the seed from the erect-ear plot has shown markedly poorer germination but this is not always the case, depend- ing naturally upon the seasonal conditions with regard to rain and freezing during the fall. According to the prevailing opinion there is another advantage in the declining ear and this is the greater convenience that such an ear affords in husking from the standing stalk. If however the corn is harvested with a machine the hanging ear is likely to cause trouble, especially if the shank is very long. So it seems that in this particular the case is like that of a great many others, the desirability of the character will depend upon cir- cumstances, and it is of interest to know that the character is suscep- tible of modification and to a large extent under the control of the breeder. LIST OF BULLETINS OF THE ILLINOIS EXPERIMENT STATION RELATING TO CORN BREEDING *Bulletin No 21. Horticulture; A General Report; Corn Crossing; Sweet Corn, Thickness of Planting, 1891 ; the Late Season and the Corn Crop. *Bulletin No. 53. The Chemistry of the Corn Kernel. * Bulletin No. 55. Improvement in the Chemical Composition of the Corn Ker- nel. ^Bulletin No. 63. Seed Corn and Some Standard Varieties for Illinois. * Bulletin No. 82. Methods of Corn Breeding. Bulletin No. 87. The Structure of the Corn Kernel and the Composition of its Different Parts. Bulletin No. 100. Directions for the Breeding of Corn, Including Methods for the Prevention of In-Breeding. Bulletin No. 128. Ten Generations of Corn Breeding. Bulletin No. 132. The Effect of Selection upon Certain Physical Characters in the Corn Plant. "Not available for distribution 61 62 BULLETIN No. 132 [February, /pop. H 5 < 3 OH < w I a I < 5 o w W en H w ^ u o x H P ~ H < CM 2 PO < H I