L1BRAR\ \Te ir^LANi BOARD E-522 January 1941 U.S. DEPARTMENT OF AGRICULTURE BUREAU OF ENTOMOLOGY AND // PLANT QUARANTINE PHYSIOLOGIC RACES OF PUCCINIA GRAMINIS IN THE UNITED STATES IN 1939 1 By E. C. Stakman and W. Q. Loegering, * Division of Plant Disease Control Introduction For more than 20 years annual physiologic race surveys of P uccinia gramin is have been made in the United States to determine the prevalence, geographic distribution, and population trends of the various known races of P uccinia graminis and to find out whether new ones arise. The results are valuable in epidemiology studies, in explaining varietal behavior, and in breeding resistant varieties. It seems desirable, therefore, to make the re- sults available each year in printed or multigraphed summaries. The results for 1939 are given in tables 1 to 9 of this report. iCooperative investigations between the United States Department of Agriculture and the Minnesota Agricultural Experiment Station. Paper No. 1840 of the Scientific Journal Series of the Minnesota Agricultural Experiment Station. Assistance in the preparation of these materials was furnished by the personnel of the Work Projects Administration, Official Project 65-1-71-140, Subproject No. 458. Sponsored by the University of Minnesota, 1939 and 1940. zUnfortunately, it would require too much space to give individual credit to all those who have cooperated in this survey by sending collections of rusted material. Most of the collections were made by the personnel of the barberry eradication project of the Division of Plant Disease Control. Bureau of Ento- mology and Plant Quarantine, especially the State leaders and men working under their direction. As in the past, W. T. Butler, agent, collected a very large number of samples throughout the Mississippi Valley. Several members of the Division of Cereal Crops and Diseases, Bureau of Plant Industry, also made collections, especially H. B. Humphrey, J. A. Clark, C. 0. Johnston, E. S. McFadden, and I. M. Atkins. Donald G. Fletcher, executive secretary of the Conference for the Prevention of Grain Rust, also furnished collections. Thanks are due all these individuals for making it possible to conduct the survey on an adequate scale. - 2 - Explanation of Terminology The meaning of some of the terms may not be clear without explanation. A collection of stem rust is an indefinite quantity of infected host material collected within a limited locality. In the case of the uredial stage, a col- lection may consist of only one or a fev/ pustules on a single plant, when rust is scarce, or it may consist of many pustules on several stems, leaves, and heads collected in a single field. In the case of the aecial stage, a col- lection consists of one to many infected leaves from a single barberry bush or group of bushes growing near each other. When rust from a collection is used to inoculate seedling plants of 12 differential wheat varieties, the resulting type of pustule, known as infection type 1, 2, 3, etc., forms the basis for identifying the race or races in that particular collection. These infection types have been described in detail by Stakman and Levine,3 who also outline the method of identifying races. It should be remembered that under the normal range of conditions in which race identifications are made, a given race will produce the same general pustule type on a given differential host; but variations in conditions, especially light and temperature, may result in corresponding variations in pustule types. It is necessary to use the word "isolate" because two or more races often are isolated from a single collection of rust, as illustrated in figure 1. Figure 1 represents the results of inoculating the differential varieties of wheat with the rust as it was obtained from the field. There are two in- fection types on Marquis, types 4 and 2. Obviously, therefore, there are at least two races present. On Reliance there are type-4 pustules only, but the number is only about 33 percent of the total number of pustules on Marquis. On Arnautka, Mindum, Spelmar, and Einkorn the number of type-1 pustules corre- sponds with the total number of pustules on Reliance. It seems likely, there- fore, that the race causing the large pustules on Reliance is causing the small ones on the three durums and Einkorn. It would seem that it might also te pro- ducing the type-2 pustules on Marquis, but knowledge of races makes this seem doubtful. The most likely combinations would te races 17, 19, and 56, but this is not certain. Therefore inoculations were made as indicated in the diagram, and the results prove that this surmise was correct. In this case, then, three isolations were made: Isolate I proved to be pure race 19; isolate II was pure race 56; and isolate III contained both race 19 and race 17, the only difference being that 17 produces type-4 pustules on Marquis and 19 produces type-2. It turns out, then, that three isolates were obtained from this col- lection of rust. In a given collection the number of isolates or isolations corresponds with the number of races identified. In the illustration chosen, for example, several other methods could have been used for arriving at the same result. A limited number of the differential varieties, known as a "half ser- ies," could have been inoculated with rust from the type-1 pustules on the aStakman, E. C, and M. N. Levine. The determination of biologic forms of Puccinia graminis on Triticum spp. Minn. Agr. Expt. Sta. Tech. Bull. 8. 10 pp., illus. 1922. (Mimeographed keys and tables for identifying races are available. ) - 3 - three durums or Einkorn (after increasing the rust on a susceptible variety to obtain enough inoculum), but race 56 would have been identified from these isolations as it was when transfers were made from Reliance. Even though race 56 had been obtained in several series of isolations from one collection, it still would count as one isolate. A "half series" is shown in figure 1 and includes the varieties Marquis, Reliance, Kota, Arnautka, Kubanka, and Einkorn. From long experience it has been found that Arnautka, Mindum, and Spelmar react alike to practically all the common races of stem rust, as do Kubanka and Acme.* Therefore, after ob- serving similar mixtures of type-4 and type-1 pustules on Arnautka, Mindum, and Spelmar, and complete susceptibility on Kubanka and Acme, it is sufficient to inoculate one variety from each group. Arnautka and Kubanka are commonly used for this purpose. In the case of Vernal and Khapli, which were completely resistant in the illustrations used, it must be concluded that these two varie- ties are resistant to all races in the mixture and need not be tested further. If either of these varieties shows a mixture of two infection types, then that particular variety must be included in the "half series." If there is doubt in any case concerning an identification made on the basis of a "half series," the isolate is tested on a complete series of differentials. In the summaries, the percentage figure given for each race simply indi- cates the relation between the number of times that that race was identified and the number of times all races were identified. For example, race 19 was isolated 40 times in the United States, and the total number of isolates was 1,158 (table 3); hence race 19 constituted 3.4 percent of all race isolates in the United States. It is important to keep in mind, however, that the percent- ages given in such summary tables as table 2 merely indicate the number of times each race was identified in relation to the number of times all races were identified. Consider race 56 in table 2 (uredial) and table 4. It was identi- fied 590 times, and a total of 1,063 identifications were made of 14 races in 735 collections; that is, there were 1,063 isolates from 735 collections. Accordingly, race 56 constituted 55.5 percent of all isolates. However, it should be remembered that the percentage figures in the summary tables might be on the basis of number of field collections rather than number of isolates. For example, race 56 was isolated from 590 collections of stem rust out of a total of 735 collections, or from 80 percent of the collections. Neither the percentage of total isolates nor the percentage of col- lections in which each race was found necessarily shows the relative amount of inoculum of that race in the stem rust collections identified in the survey. If it were desired to arrive at this, the proportion of each race in each col- lection would first have to be computed on the basis of number of pustules pro- duced on one or more of the differential varieties by one race in comparison with the number of pustules produced by the other race or races present. For example, assume the presence of races 19 and 56 in a collection, as shown in figure 2. In this case the ratio of race 56 to race 19 is 70:30, that is, race 55 constitutes 70 percent of the rust, and race 19 constitutes 30 percent. ^Especially those concerned in the present report. Similarly, in figure 1 it can be seen that the amounts of races 17, 19, and 56 were approximately in the ratio of 33:33:53. Following this procedure with each identification, an attempt could be made to arrive at the relative amount of inoculum of at least the more common races in the collections as a whole. Thus, in 1939 race 56 constituted by far the largest proportion of the rust in the collections in which this race was mixed with other races. Collections from Barberry The three varieties of Puccinia graminis that attack small grains were well represented in the aecial collections (table 1). Forty-six percent of the 173 varietal isolates proved to be wheat stem rust (P. g raminis tritici) , 34 percent were rye stem rust (P. graroinis s ecalis ) , and about 20 percent were the oats stem rust (P. graminis avenae) . These results show clearly that these three varieties all develop on barberries and that epidemics of stem rust can occur on any of the small grains as a result of spread from barberry. Races of Puccinia graminis t ritici It can be seen from tables 2, 3, 4, and 5 that 1,063 isolations of 14 races of Puc cinia gr aminis tritici were made from 735 collections of uredial material and 95 isolations of 17 races were made from 80 collections of aecial material. This means that, on an average, a different race was identified in every 76 uredial isolates (a ratio of 1:76) and a different race was identified in every 6 aecial isolates (a ratio of 1:6). This shows again, of course, the role that barberries play in producing and perpetuating physiologic races of P. gr amini s. s, e Despite the fairly large number of races identified, races 56, 38, 17, 19, and 11 combined constituted upward of 95 percent of all the isolates, and the first three constituted almost 90 percent. For the sixth successive year, race 567 was the most prevalent, constituting 55.5 percent of all the uredial isolates and 32.5 percent of all the aecial isolates, or about 54 percent of all isolates. It was isolated from about 80 percent of all uredial collections, which is somewhat of a decrease in prevalence from that of 1938, when it constituted 66 percent of all isolates and was found in about 83 percent of the collections. The relative amount of inoculum of race 56 also was somewhat less than in 1938. sStakman, E. C, and R. C. Cassell. The increase and importance of race 56 of Puccinia g raminis tritici (Abs.). Phytopath. 28: 20. 1938. 6Stakman, E. C, Lee Hires, Robert C. Cassell, and M. N. Levine. Popu- lation trends of physiologic forms of Pucc inia gram inis tritici , 1930 to 1934 (Abs.). Phytopath. 25; 34. 1935. 7Stakman, E. C, R. C. Cassell, and W. Q. Loegering. Population trends of physiologic races of Puc cinia gra minis tritici in the United States from 1930 to 1939 (Abs.). Phytopath. 30: 22. 1940. Race 56, however, was still by far the most prevalent race in North Dakota, South Dakota, Nebraska, Minnesota, and Iowa, where it was obtained from 92 per- cent of all uredial collections. This race, as is probably common knowledge, attacks Ceres and Kota wheats very severely and was responsible for the almost com- plete elimination of Ceres as a commercial variety in the spring-wheat area. Race 38, which attacks the soft winter wheats and durum varieties, ranked second in prevalence, having been identified in 24 percent of the uredial iso- lates and in 15 percent of the aecial isolates, or 23 percent of all isolates. Race 38 was particularly prevalent in the eastern part of the barberry-eradica- tion area, just as 56 was very prevalent in the spring-wheat region and adjacent Nebraska and Iowa. The increase in prevalence of race 17, which has been showing a tendency to increase gradually for a number of years, seems significant. This race com- prised 3 percent of the uredial isolates in 1938 and 10 percent in 1939. It was second in prevalence in aecial material, constituting about 19 percent of the isolates. This race attacks most of the durum and common wheats severely, with the exception of certain varieties derived from Kanred, among which is Thatcher. The next most prevalent races were 19 and 11, but each constitutes only about 3 percent of all isolates. Race 19 behaves much like race 38 but does not attack Kanred wheat. Race 11 attacks all the differential varieties except the emmers. None of the other races were present in large amounts. One of the most conspicuous tendencies during the last few years has been the gradual decrease of races 21 and 36. It appeared for a time as if race 21 would not appear in uredial collections, but finally four isolates were obtained, including one from western North Dakota, where race 36 was also found. It was suspected that barberries must have been present in the region, and an inquiry was made. Heavily rusted barberries were found at Sanger, N. Dak. , in 1940, and it seems likely that the collections of races 21 and 36 made in 1939 probably came from rust developed on these barberries in that year. This is a good example of the danger of barberries in the prairies and plains region and indicates also that clues to the existence of barberry bushes may be obtained by race identifica- tions. Some other noteworthy facts are given below with respect to uredial iso- lates. R ace 36 , 8 isolates or 0.8 percent . — This race, which has about the same host range as race 56, was found in areas where we might expect barberries to be present, as in Minnesota, Missouri, Iowa, and Virginia. One collection from North Dakota probably originated on the barberries at Sanger as mentioned above. Two collections were also made in Washington. R ace _ 1 47, .8 isolates or 0. 8 perce nt. — The distribution of race 147 in 1939 was scattered. It was collected three times in Indiana, twice each in Ohio and Texas, and once in Pennsylvania (perhaps originating on barberry). This race behaves ''ike 56 except that it can attack Vernal emmer also. grrKT ^T.SVa«p Race 54. 6 isolates or 0.6 p e rce nt. — This once prevalent race was isolat- ed in collections from Michigan, Minnesota, Missouri, and Ohio. Race 4 9. 6 isolates or .6 percent. — Race 49 was isolated once from material collected in each of the States of Texas, Oklahoma, Kansas, Missouri, Indiana, and Iowa. It was very prevalent before race 56 became so common and differs from 56 by being unable to attack Kanred. Race 59, 5.. isolates or .5 percent . — Race 59 was obtained from the five eastern States of Georgia, Ohio, Pennsylvania, Virginia, and West Virginia. It attacks only Kubanka, Acme, and Einkorn wheat and is very common in southern Mexico. Race 21, 4 isolates or .4 percent . — One isolate of this race was col- lected in North Dakota in the same general area in v/hich race 36 was found, and one was found in each of the States of Wisconsin, West Virginia, and New York. Race 15, 5 isolates or 0.5 percent . — This race was found in Indiana, South Dakota, and Wisconsin. It has a wide host range, attacking all the dif- ferential varieties except Khapli emmer wheat. Race 24. 2 iso l ates or 0.2 percent . — Race 24 was isolated from Iowa and Texas collections. Race 14, 1 isolate or 0.1 percent . — Found only in Wisconsin. North_Dakota Uredial Collections During 1939 a special effort was made to identify the variety of v/heat on which stem rust was collected in North Dakota. These collections are classi- fied under the heading of "common wheat and barley" and "durum wheat," and the isolations from each group are given below: 51 collections of common wheat and barle y 9 collections of durum wheat Race No. of Percent of isolated isolates collections 56 51 100.0 17 7 13.7 38 5 9.8 21 1 2.0 36 1 2.0 Race No. of isolated isolates 38 6 19 5 56 1 Percent of collections 66.7 55.6 1.1 It is obvious from these figures that race 56 was found on all the com- mon wheats and barley on which stem rust was collected in North Dakota. Most of the collections included in the first group shown above were Ceres, and, as would be expected, race 56 was isolated from 100 percent of them, while very little race 56 was obtained from the durums. From 9 durum collections race 56 was isolated only once, in contrast with 11 isolations of races 38 and 19 from the same collections. The durums, as may be known, are quite susceptible to races 38 and 19, while the common spring wheats are resistant or semiresistant . - 7 - Barberr y Collections Eighty isolations of P uccinia graminis tritici were obtained from aecial collections in 1939, from which 95 racial isolates were made, representing 17 different races (tables 2 and 5). Races 56, 17, and 38 made up 66.1 percent of all isolates, representing 32.5 percent, 18.9 percent, and 14.7 percent, re- spectively. It should be noted that race 17 was more prevalent in aecial col- lections this year than in 1938, as was also true of uredial collections. Fur- thermore, race 17 was more common than race 38 in barberry material, while in uredial collections race 17 occurred less than half as often as race 38. Race 59 was fourth in prevalence in the barberry collections, constituting 6.3 per- cent, as compared with the relatively low percentage of 0.5 in uredial collec- tions. It is worthy of note that five of these isolations were made in the central-western States where race 59 was not obtained from uredial collections. Other races, 11. 19, 21, 34, 36, and 49, all quite common from field uredial collections at one time or another, were isolated in a relatively small per- centage of the collections on barberry. In addition, races 14, 15, 55, 71, 79, 115, and 147 also were isolated. These seldom are found in uredial collections in the United States; indeed, some of them never have been collected except on barberry. It is significant, also, that of these seven races, five (15, 55, 79, 115, and 147) attack Vernal. Races of Puccinia graminis avenae During the 1939 stem rust survey 440 collections of oats stem rust were received, including rust on oats, on grasses susceptible to the oats stem rust, and on barberry (tables 7, 8, and 9). From these, successful inoculations were made with 250, from which 251 racial isolates were made. From only one col- lection was more than one race isolated. As in the past, races 2 and 5 were by far the most prevalent, making up together 96.8 percent of all isolations. Race 2 was slightly more prevalent, constituting 55.8 percent compared with 41 percent of race 5. However, these two races are so similar that they may easily be mistaken for each other, and therefore for general consideration the difference in percentage is not par- ticularly significant. The isolation of races 7, 8, 10, and 12 is interesting. Races 7 and 8 were isolated three times each and 10 and 12 once each. One isolate each of races 7, 10, and 12 were found in Pennsylvania and came from barberry or near barberry. The remaining two isolates of race 7 and the three of race 8, how- ever, were not collected near barberry. They were found as follows: Race 7 from the Uniform Oat Rust Nurseries in Wisconsin and Oklahoma, and race 8 near Chillicothe, Mo., Springfield, Ohio, and Forest, Wis. Races of Puccinia graminis secalis Relatively little stem rust was found on rye in the course of the 1939 survey except in the immediate vicinity of barberries, again emphasizing, as has been stated frequently, that this rust can be controlled for all practical purposes by the eradication of barberries. - 8 - As very little attempt has been made to produce rust-resistant varieties of rye, detailed race identifications of this rust were not made. However, Puccinia graminis secalis was isolated from three collections of stem rust on barley, one in Minnesota, one in New York, and one in Pennsylvania. Ralph U. Cotter identified the race in the latter collection as P, graminis secalis, race 11. P. graminis tritici , races 56 and 11, also were isolated from this collection. General Conclusions It is evident from the results of the survey in 1939, especially when compared with the results of previous years, that the comparative populations of races of Puccinia graminis tritici may fluctuate considerably. For example, taking the past 10 years, it is clear that some races such as race 11 have fluctuated considerably, ranging from 22 percent of all uredial isolates in 1931 to 3.2 percent in 1939. Race 21 was far more prevalent in the first 5 years of the decade than in the last 5 years. Race 36 ranked first in 1930 and 1931, with 36 and 28 percent of the isolates respectively; in 1934 it constituted 21 percent; while in 1939 only 0.8 percent of all uredial isolates were race 36. Race 49 was prevalent during the first 4 years of the decade beginning 1930 and has shown a tendency to decrease since that time. Race 56 was very scarce in the first 4 years of the decade, but has ranked first for 6 consecutive years, the high having been reached in 1938 v/hen it exceeded 66 percent of all uredial isolates. Race 17 also has shown a tendency to increase, but much more slowly than 56. Race 34 increased gradually until it reached a maximum of 22 percent of all uredial isolates in 1934, and since that time it has shown a tendency to decrease gradually until it was negligible in 1939. Obviously, with a decided tendency toward population shifts in physiologic races, it is inevitable that certain varieties that are now quite resistant to rust may rust much more heavily if certain races increase in prevalence in the future, and the converse also is true. As concerns Puccinia graminis avenae , races 2 and 5 have long been by far the most prevalent races, together constituting 97 percent of all isolates in 1939. The isolation of races 7, 8, 10, and 12 in 1939 indicates that these races may become more widely distributed and more prevalent in the future. 9 - Table 1. — Varieties of Puccinia Rraminis isolated from aecial collections in the United States in 1939 Rust variety Number of isolates Percent P. graminis tritici P. graminis secalis P. graminis avenae 80 59 34 46.2 34.1 19.7 Totals 173 100.0 Table 2. — Physiologic races of Puccinia graminis tritici isolated from uredial and aecial collections in the United States in 1939 J R E D I A L A E C I A L UREDIAL AND AECIAL No. of No . of No of Race isolates Pet. Race isolates Pet. Race isolates Pet. 56 590 55.5 56 31 32.5 56 621 53.6 38 255 24.0 17 18 18.9 38 269 23.2 17 106 10.0 38 14 14.7 17 124 10.8 19 35 3.3 59 6 6.3 19 40 3.4 11 34 3.2 19 5 5.3 11 36 3.1 36 8 0.8 14 3 3.2 59 11 0.9 147 8 0.8 15 3 3.2 147 10 0.9 34 6 0.6 49 3 3.2 36 9 0.8 49 6 0.6 11 2 2.1 49 9 0.8 59 5 0.5 21 2 2.1 34 7 0.6 21 4 0.4 147 2 2.1 15 6 0.5 15 3 0.3 34 1 . 1 21 6 0.5 24 2 0.2 36 14 4 0.3 14 1 0.1 55 71 79 115 1 .1 24 55 71 79 115 2 1 1 1 1 0.2 0.1 0.1 0.1 0.1 14 1,063 100.3 17 95 100.2 18 1.158 100.0 Ratio of races to isolates, 1:75.9 Ratio of races to isolates, 1:5.6 nJ 1 oi u (D XI e 1 PI c3 c O nHi W .'^l M ^C\iMint-oCDC\i£>COOTl<^tDt~lOTtr-i(£)C^t--|C£>0'H > •" r-1 o uj r^j "-^ fj w >— I vi-i fj i.\^ ij: uj ■— ' ^ X; .s ■^ /n ■-it-^o "^to-Hio ocD^cD inoo^f ^co --i w lo '-^'^WC£l WCDOOtO 00'<4<<^lO M-CDW tOtO ^ 73 !> 1 1 1 > to 1 1 1 1 1 1 1 1 1 Cvi 1 w 1 I W 1 1 1 r-i 1 o rH C ^ 1 1 1 1 1 ^ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 rH R} M •H nH O O (T) 1 1 1 1 1 ^ 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 rH 0) ^ i iH 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ^ 1 1 1 1 1 1 1 1 r-< ^ 1 rH 1 -^ 1 1 1 1 I C\i 1 1 1 1 rH 1 ,H 1 rH 1 rH 1 CM rH 1 r-i cc CV 1 W t- C\2 rf CD nH in rH CO -^ w O O to in rH CD rH C\2 1 00 in to CV CD O OJ (D lO to w in cv 00 in to t> to c\J w to ^ w rH C\i -H" +-> Cti to 1 1 i > 1 1 1 1 1 1 1 1 1 1 1 1 rH i 1 1 1 1 1 1 1 rH ■H W r-H in o O ■H >j CO -t-' Xi • H 0^ 1 1 1 1 rH ^ ^ 1 1 rH rH 1 1 1 1 rH CVi 1 1 -H 1 1 1 1 1 CD •H ^ f-. « CO ■tJ U) i to rH C\i C\J C\2 r-\ (^2 ,-{ ■H iH +J C\J C Cm CD 1 1 ' 1 1 -H 1 1 rH rH rH | 1 rH 1 1 1 1 1 rH rH C\2 1 1 1 CD s •H O to (d tn CO (h w © © -^ 1 1 1 1 1 1 1 1 rH C\2 rH 1 1 1 W 1 rH 1 1 1 1 1 1 1 1 t> -(-> J3 to rt 03 B •H -t-> ;3 c C/2 c ■<^ 1 1 1 1 1 rH 1 1 1 1 1 1 1 1 1 1 1 1 1 -H 1 1 1 1 1 OJ •H CV2 o T3 T3 o © C 3 -t-> cd iH 1 1 1 1 1 1 1 1 1 1 1 1 iH rH 1 1 CVi 1 1 1 1 1 rH rH 1 CD ft. •H C\J c © ^ D o o a cn 1 1 1 '-< 1 1 to 1 c\2 1 in 1 ,-H in cvi 1 ^ 1 CJ CO M* 1 1 to 1 O DC rH ■^ (0 X3 © -fj o b- C\2 1 1 --• in cv CD 1 -^ C\i (D CD 1 rH Tf t-- in 1 00 lO rH 1 ^ C\2 1 ■^ rt a rH C\2 r-i tH rH C\2 f-. -H i-{ O CO in 1 1 1 1 nH nH 1 1 1 1 rH 1 1 1 1 1 rH 1 rH 1 1 1 1 rH 1 CD •H G r-1 txO O O -H iH +J ^ 1 1 1 i 1 1 1 1 1 1 rH 1 1 1 1 1 rH 1 1 1 1 1 1 CV 1 ^ o o r-< ■H 3 i-H r-l rH 1 1 1 to to CD 1 rH ^J* .H CV 1 1 1 "^ rH 1 1 in rH 1 •-^ to 1 CD x: o rH to 0- o 1 <3 a o o iH (d X ^ O OT >5 c •+-> -H cd ^ cd & X3 (d •'^ (d 4*: td o (-. ^ (-. 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Q a rH Q bfl •H CO bO cd •H e CT bJ3 CO :2 CO >5 c G > PI jrj CO f- 'oO s k3 a ri •H Q) a >• xi x: CO ^ xi CO ■t-t ■H !_( XI •H •H ri CO +-> -c: c: CO u cd d +-> +j cd bO x: -p a cd 1— 1 cd i-H t3 ^ a c u cr> X! > r_. •H <-^ G 13 1=1 X u, CO CO CO ^ 0) T3 rH ^ nj (!) -n ■H •r-,' CD XI X © © ■H cd © •H ^ M M M rH ti; 1^ S S s 2: ^ s y) 0; tr-' > ^ & E- ri>oiinc-ic^c a. -H 1-1 I lin 10) T3I a.) to PllO -Hi o ir> CO in 01 ^1 ^ito ci 1 OlO) 0|rH cdl ILO r C\2 I rH I I I H I I I I 1 I I I I C\2 C\2 I ,H lO 1 W I cv a> I I I '^ I 1 I I I I I I I I I ■H I I I I I t I I I in I rH rH -^ rH I I I I I --H I I a •H ■H +-> G CO -H c6 X to a > nj 0} fn -H rH Q -H -H CO C P --H (ti cj a o f- X C txO CO 3 to r3 HCDOrt COJ^-H O •Hn3A::CC0^.O C-PbO-PO 'dEsoc:cOrQHC:3t-icoco C; O -H -H -H &S - 13 - Table 6. — Physiologic races of Puccinia Rraminis avenae isolated from uredial and aecial collections in the United States, in 1939 UREDIAL AECIAL UREJIAL and AECIAL No. of No . of No . of Race isolates Pet. Race isolates Pet. Race isolates Pet. 2 125 56.5 2 15 50.0 2 140 55.7 5 89 40.2 5 14 46.6 5 103 41.6 7 3 1.3 12 1 3.3 7 3 1.2 8 3 1.3 8 3 1.2 10 1 0.4 10 12 1 1 0.3 0.3 5 221 99.7 3 30 99.9 6 251 100.3 Ratio of races to isolates, 1:44.2 Ratio of races to isolates, 1:10 Table 7. — Physiologic races of Puccinia graminis avenae isolated from aecial and uredial collections in the United States in 1939, by States Race and number of times isolate d State 2 5 7 8 10 12 California Colorado Florida Illinois Indiana Iowa Kansas Louisiana Maryland Michigan Minnesota Missouri Nebraska North Dakota Ohio Oklahoma Oregon Pennsylvania South Dakota Texas Wisconsin 3 8 2 9 28 14 4 5 11 2 1 26 4 12 2 4 3 2 1 5 12 8 2 8 6 1 1 33 1 3 10 1 - 1 1 - Total number Collec tions Isolations Races 1 1 1 1 2 7 2 11 11 2 4 2 1 1 14 14 2 40 40 2 23 23 3 6 6 2 13 13 2 18 18 3 4 4 3 2 2 2 61 62 5 5 5 2 15 15 2 20 20 4 Totals 140 103 3 3 1 1 * From Uniform Rust Nursery. 250 251 14 Table 8. — Physiologic races of Puccinia Rraminis avenae isolated from uredial collections in the United States in 1939, by States Race and number of times isolate d State 2 5 7 8 10 California 1 - Florida - 1 Illinois 1 - Indiana - 1 Iowa 3 4 Kansas 8 3 Louisiana 2 2 Michigan 9 5 Minnesota 27 11 Missouri 14 8 Nebraska 4 2 North Dakota 5 8 Ohio 11 6 Oklahoma 2 1 Oregon 1 1 Pennsylvania 13 24 South Dakota 4 1 Texas 12 3 Wisconsin 8 8 Totals 125 89 1 1 1 1 Total number Collections Isolations Races 1 1 1 1 2 11 11 2 4 4 2 14 14 2 38 38 2 23 23 3 6 6 2 13 13 2 18 18 3 4 4 3 2 2 2 39 39 4 5 5 2 15 15 2 18 18 4 221 221 Table 9. — Physiologic races of P uccinia graminis avenae isolated from aecial collections in the United States in 1939, by States Race and number o 2 f times 5 12 Total number State Collect ions ISO lations Races Colorado ' 1 _ _ 1 1 1 Indiana - 1 - 1 1 1 Maryland - 1 - 1 1 1 Minnesota 1 1 - 2 2 2 Pennsylvania 13 9 1 22 23 3 Wisconsin - 2 - 2 2 1 Totals 15 14 29 30 < Ul ^ a < z a o < Z u z < UJ ae ^ 1- z z UJ m Z < liJ o oc a 3 u z Z 0^ ^ < Z O) ^ < lij Original inoculation \^ from field ^^j collection ISOLATE m ISOLATE n ISOLATE I M w A A A (i\ A ^ A A A A A A = ? _Race I7&i9 Race 56 _Race ~ 19 Figure 1. Diagram showing method of isolating races from a mixed field collection UNIVERSITY OF FLORIDA iifl'lf^'^'fliii 3 1262 09224 7682