Studies of the pathogenic potentialities of puccinia graminis avenae and genetics of resistance in oats

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(1)AGROPECUARIO O COLOMBIANO[T C A DE FITOFATOLO:. DIES OF THE AT H O G E N lo :NTIALITIES OF INIA GRAMINIS E AND GENETICS OF RESISTANCE IN OATS PL. 480 PROJECT FG - Co - 106. a FINAL. l2t P. 20 FEBRUARY 1962 20 FEBRUARY 1967.

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(3) 1. TITLE PACE FINAL REPORT. P.L. 480 Project FG-Co106 20 February 1967 1. Name and address of reporting institution. 2. a. Name of principal investigator b. Name of investigator. Instituto Colombiano Agropecuario "ICA" Tibaitatá Apartado Aéreo 5813 Bogotá, Colombia : Dr. Juán Orjue1a-N Ing. Agr. Elkin Bustamante-R. Ing. Agr. Hernán Ramírez-A.. e. Name of visiting pathologist. Dr. J. Artie Browning. d.. Name of visiting plant breeder. Dr. K. J. Frey. e.. Names of cooperating scientists. Dr. H. David Thurston Dr. Guillermo Gálvez-E. Dr. Charles F. Krull Dr. John W. Gibler Ing. Agr. Reinaldo Reyes-N. Ing. Agr, Jesús Arias-F.. 3.. Project titie. Studies of the pathogenic potentialities of Puccinia graminis avenae (oat stem rust) and genetics of resistance in oats.. 4.. Grant number. FG-Co-106. S. Dates of research period covered by report. 20 February 1962 - 20 February 1967.

(4) TABLE OF CONTENTS. Page 1. II. III.. Titie Page Summary of oat stem rust situation in Colombia. 1. Detailed report. 3. 1.. Introduction. 3. 2.. Results. 3. A.. Greenhouse experiments at Tibaitatá. 3. B. Field experiments at Tibaitatá. 27. C. Work in Nariño, Antioquia and Puerto Rico.. 37. 3.. Discussion. 40. 4.. Conclusions. 43. S.. Publication. 46.

(5) -1-. II. SUMMARY OF OAT STEM RUST SITUATION IN COLOMBIA. In 1955 the Colombian breeding program for the improvement of oats was initiated with the purpose of obtaining varieties with better agronomic. characteristics and resistance to stem rust. The program was frustrated by. the attacks of the fungus Puccinia graminis Pers. f.sp avenae Eriks and Henn to the point that it was necessary to suspend the program due to the lack of genetic sources of res istance useful in the improvement program.. Because of this situation an intensive study was initiated in 1958 on the characteristics of the pathogen. This study included the identifica-. tion of races and sub-races present in the country, their prevalence and. their virulence on the known oat genotypes. These studies made possible the reinitiation of the oat breeding program, and resistant varieties were found with valuable agronomic characters. Studies on the identification of races of P.. avenae have .shown to. date the presence. of 7 races and 38 sub-races including the sub-race 6C. which has a very wide host range. An additionai group of sub-races has been found in the last few months attacking the best varieties obtained.

(6) -2by the Oat Breeding and Plant Pathology Programs0 Investigations carried out to determlnethe influence cf light on the development of stem rust have shown that varieties with gene D are light sensitive and that when grown under high light conditions their reaction changes from resistant to susceptible. Lines with the F gene are also light sensitive, while unes with genes A and B are not sensitive to light. These results are from experiments made under greenhouse and growth cabinets conditions. Field experiments made to correlate the greenhouse and growth cabinets results showed that a real light influence occurred. Howeve; these differences are so small that they are distinguish under certain environmental conditjoris. The ICA-BACATA variety was distributed in1965 to Colombian growers because of its outstanding characteristics such as early maturity, high forage yields, good protein content and moderate resistance toraces at that time present of Pucciniá graminis avenae: However, shortly after its introduction, a severe attack of stem rust occurred on ICA-BACATA and the sub-race 3-D-2 was determined as responsible for this attack0.

(7) -3-. Subsequently other sub-races have appeared attacking this sarne variety. Fortunately, sorne ICA•-BACATA plants were found free of rust in the fleid. and were selected for further testing in the greenhouse and. the fleid.. Good sources of resistance to the new races have been found in this way.. III. DETAILED REPORT. It is well known that the greatest obstac.le to oat production in Colombia and in general throughout the Andean zone ls .stem rust caused by Puccinia graminis avenae. These studies have given a better understanding of the pathogen and its behavior under local conditions. Adequate solutions have not yet been devised to increase oat grain production, but it is now possible to produce forage with hlgh yields. Experirnents. have shown that oats can be grown at different elevations. These findings open Che possibility of producing oats for hurnan consurnption. 1. Results:. A. Greenhouse Experirnents. 1) Identification of races of Puecinia graminis avenae In 1960 under greenhouse conditions 148 coflections of P. V ,. avenae.

(8) -4from oats and various grasses were studies. Eight races and 30 sub-races were identified (Table 1). Races 4, 6, 13, and 3 constituted 97 percent of the races. With the exception of sub-races 4A, 6A and 13A, the other races were new or had never been previously described. English ryegrass (Lollium perenne L.) and orchard grass (Dactylis glomerata L.) were shown to be important hosts of the most common sub-races (4A, 6A and 13B) of P. avenae at Tibaitat. The most important races in 1961 were: 13, 6 and 12 (Table 2). In. 1962, from 1550 single pustule isolates coliections 7 races arid 33 sub-races were identified. Of the collections studied 25 percent were taken from wild oats (Avena fatua Le) orchard grass (Dactylis glomerata L.) and ballico (Lollium temulentum L.) (Table 3)e From the 33 sub-races identified, 21 have been described previously and 12 appeared for the first time, but none of them was more pathogenic than those previously described. Race 6 was the most prevalent, followed by races 7 and 13. Races 3, 7 and 12 . had also numerous sub-races..

(9) Table 1. - PATE OGENIC RACES OF PUCCINIA GRAMINIS AVEANE IDENTIFIED FROM SIÑGLE PUSTULE COLLECTIONS AT COLOMBIA (cuwnwcÁ AD BOYACÁ) DTJRING 1960. FRECUENCIES OF PACES Mil' SUBRACES. 3 BCD. 7 ABCD. 12 KBC. 4 A B C D. 91 22 5. 61 36 5 7. T O T A L. 6. A.BCD. 13. ABCD. Iso-. lates. Percen-. tages. Subraces:. Collectlons Percentages. 5 38 31. 12 11 22. 5. 0,71 14,11.3 1,71 3,15 5,11.3. 1,57 0 71. 9 11.0 145. 13 0,71 8,71 0,71 1,29 3,15. 5,15. 118. 109. 1,0. 6. 6,43. 5,71 0,86. 11 191 41. 6. 700. 1,57 6,14. cn. 27,60 o,86. ioo. Races:. Collections. 74. Percentages. 10,57. 50 7,111.. 16,86. 15,57. 100 114,29. 2149 35,57. 700 100.

(10) T&ole. 2.-. PATHOGEN1C RACES OF 1JCCIWtA GRAMINIS AVENE iDKTTIFIED FOM SINGLE PUSIULE C0LLECtONS. AT. TIBAITATA. DURING 1961. ...-...-.. .-. . . . -. . FRECtJENCIE. OF. 3. RACES. 12. AND. 7. SUBRACL3. __. TOTAL. BCD. A B C. ABCD ABCD. 6 Ac. 31 15 30. 25 77 26. 10 16. 1:571592. A. B. 13 C D. IsoPercenlates tages. Sub-races: Collectjons Pere entages. 4,4. 11,5 2,2. 11, 3 1,5 3,7. 3,8. 22. 2. 3,2 1.. 0,3. 30 33 9. L.. 11,14 1,3 11,9 0,6. 2,2. 8,7. 10,5 0,3. 8152537. RE. 1,2 0,7 22,14 5,5. 100. Races: lCollectiona. 76. Percentages. 11,2. 128. 18,8. 50. 7,4. 76 11,2. 147 21,7. 202. 29,8 .....,. 679 100. ........... ..

(11) Table. 3.-. PATHOGEIIC RAES OF RJCCINIA GRAI vaNIS AVENAE IDTIFIED FROM SINGLE RJSTULE COLLECTIONS AT TIBAITATA, DURING. 1962. TOTAL. FRECUENCIES OF RACES AJD SUBRACES. 3___. BCDEFG. ABCD. 6. 7. ABCEJ:\.BCDEFGH. A. B. 12 C. D. E. F. 13 A. Iso- PercenBCDeses. Sub-races:. 2)4)430 11 5 30)4293 79 311 39 1 9927)4)4207)4812 3)465161920 )41259161 1469 11 2,8 2,6 o,6 1,8 14,1 0,1 2,3 0,3 0,6 2,0 0,6 5,4 0,2 0,4 0,1 17,6 0,1 3,2 0,2 0,4 10,9 1,30 0 21,1 0,1 o,6 2,0 1,0 2,9 0,2. Collections Percentages. Races: Collections Percentages. 56 4,1. 74 5,7. 1130 29,2. 347 23,6. 235 15,8. 317 21,6. ioo. i469 100.

(12) -8-. The 6 races identified from the collections from Avena sativa L., were also found on the grasses mentioned abo y e in addition to the races 2 and 5 (avirulent on the differential variety Minrus). These facts illustrate the importance of grasses as hosts for P. . avenae0 In 1963 the number of sub-races decreased to 23, consisting of 7 races arnong which race 6 was the most prevalent (32.1%) and race 12 displaced races 13 and 7. Sorne collections were made in the State of Antioquia and were identified as sub-races 6B, 3G, 7C and 7E. These sub-races were of minor importance during the proceeding year and did not appear in 1963 (Table 4). In 1964 the collections for identification were reduced to a single pustule per day and only 6 races and 15 sub-races were identified Sub-race 2B appeared only once and the sub-race 7E* twice as shown in Table S. The 7E* sub-race presented a reaction type 4 on Minrus, and O; 1 on ICA-BACATA. In 1965 the rnost irnportant discovery was the appearance of a new subrace highly virulent on the ICA-BACATA variety. This race was initially.

(13) Table 4. - PATHOGENIC RACES OF PIJCCINIA GRAMINIS AVENAE IDENTIFIED FROM SINGLE PUSTULE COLLECTIONS AT TIBAITATA DURING 1963. T O T A L. FRECUENCIES OF RACES AND SUBRACES. 2. C. 3 D E. G. A. 4 B. C. AB -. 6. C. 7 F. EE*. 12 D E F. A. C. 5. 9 33 102 9 43 12 113 3 18. A. C. PerIso-cenA B C lates tages. Sub-races: Collections 12 3 10 13 26 67 20 2 79 237 1 LO. Percentages 1.2 0.3. 2.7 1.3. 2.0 0.2. 6.9. 0.9. 0.1. 8.1 23,9. .5. 4.4. 10.4 3.4. 0,9. 1.8. 11,5 1.2. 49 117 1. 0.3. 984. 11,9 5,0. 100. 0,1. Races: Collections 12. 52. 89. 317. 158. 189. 167. Percentages 1.2. 5.5. 9.1. 32.1. 16.1. 19.2. 17.0. * Infection tipe 4 on Minrus. 984 100.

(14) Table 5 PATHOGENIO RACES OP PTJCCINIA GRANINIS AVENAB IDENTIFIED FROM 3ILE PtJSIULE COLLECTIONS AT TIBAITATA DURING. 1964. T O T A L. FRECtJENCIES OF RACES AND STJBRACES. 3. CDG. 4. 6. 7. AB. AB. CEE*. 35 22. 33 34. 3 15 2. - 12. 13. ADF. AB. Iso lates. 3 8 2. 6 12. 200. Percen tages. Sub.races: Collections. ?7. Percentages. 3,5. 10. 11,0. 5,2. 17,0 16,. 17,5. 1,5. 7,5 1,0. 1,5. 6,0. 1,0 4. H lOO. 3,0. Races: Coilectjons. 25. 57. 67. 20. Percentages. 123,5. 28,5. 33,5. 10. 13 6,5. 18 9,0. 200 100.

(15) - 11 identified as sub-raee 3D* and later as 3D-2. The 31)* sub-race showed a reaction type 4 on Minrus, and ICA-BACATA This sub-race was later denominated 3D-2. (Fig. 1, 2, and 3). This sub-race became one of the most prevalent because of the large acreages of ICA-BACATA grown at Tibaitatá. This made race 3 the most cornmon race displacing races 4 and 6. Race 13 diminished considerably as wefl as races 7 and 12, (Table 6). The predominance of race 3 increased in 1966 with the appearance of a new sub-race (30-2) that with three other sub-races (7A-2, 7F-2 and 7H-2) attacked ICA-BACATA severely as did sub-race 3D-2. (Table 7). In this year only 4 races and 16 sub-races were identified. Races 13 and 12, which were comrnon in previous years, dissapeared. The changes of sorne races in the population have forced to use other sources of resistance to atternpt a solution to the stem rust problem. 2) Tests of varieties and/or unes to sub-race 6C of Puccinia graminis avenae •. As sub-race of P. 1. avenae is the most pathogenic race in Colombia, all the material produced by the oat breeding program has been tested with.

(16) - 12 -. /. 2 3 4 5 6 7. 8. fc2 5ca/Q. Figure 1. Subrace 3D* collected on variety ICA—BACATA.

(17) -1. -. ;.. Figure 2 Varity ICA—BACAT\ in a comrnercial ]ot atinckd by subrce 3D* of Puecirua gramini s nvenav.

(18) 14 -. !. ki1 tu. Figure 3. Deveopment of oat stem rust on variety ICJ\—BACATA.

(19) Tab1 6.- PATHOGENIC RACES OF JCCINIA GRAMINIS AVENAE IDTIFIED FRO SINGLE HJSJLE COLLECTIONS AT TIBAIITA DURIN& 1965. FRECUENCIES OF RACES AND SUBRACES. TOTAL. 6 712 A B C E ACEE*-F DF. 3 DD-2EG. 14 AB. 77 1 1 36 14,3 0,2 7,7. 1213. 725711. 0,6. 1,1 2,11. 13. Iso-. AB. lates. 107. 4614. Percentages. Sub-races: Collectjons Percentages. 2. 16,6 0,2. 26,1. 15,5 1,5. 18 It 13 16 32 436 0,9 3,14 0,9 3,9 2,8. 6,9. 1,3. 2,2. 1-'. 1,5. 100. Races: Collectjons Percentages. 135 29,1. 1214 26,7. 95 20,5. 83 17,9. 10 2,1. 17 3,7. 4614 100.

(20) Tabla 7.- PATHOGEI'IC RACES OF PUCCINIA GRAMINIS AVENAE IDENTIFIED OF SINGLE PUSTULE COLLECTIONS AT TIBAITPTA DTJPING 1966. FRECtUENCIES OF RACES AND SUBRACES. 3. 14. 6. TOTAL. 7. D D-2 E G G-2. A C. A B C. A-2 E E* F F-2 H-2. 2 91 1 23 614. 23 1. 114 3 7. 11 2 2 31 23 5. Iso-. Tes. Per centages. Sub-races: Collect jons Perc ent ages. 0,6. 0,3 30,0. 0,3. 21,0. 7,9. 1,0 4,6 2,3. 7,9. 14,0. 0,6. 0,6 10,2. 303. 7,9 ioo. 1,6. Races: Collections Percentages. 181 59,7. 214 7,9. 214 7,9. 74 214,142. 303. 100. o'.

(21) - 17 this race in different stages of plant developrnent. Initially 50 unes were tested in 1962, of which 35 were completely suceptible and 15 showed a moderate resistance. Later the yields of these moderately resistant unes were compared, The Unes were artificially inoculated with P. avenae. with appropriate checks. It was shown that moderately resistant lineE showed very little difference in production ±.n relation to non-inoculated plants; but that unes ciassified as very susceptible had very low yields in comparison with the non-inoculated plants. Likewise 510 varieties froni the International Oats Rust Nursery and from the world collection were tested; only 8% cf this material was moderately suceptible. In 1963, 89 unes selected by the oat breeding prograrn in Tibaitat were tested. Twenty of thern were highly susceptible and 69 had moderate resistance to moderate susceptibility. Sorne unes from Iowa which were crossed with CI 3030 showed the best resistance to race 6C (infection type 2-2) at a temperature of 64.40F. Sorne of thern ga y e a susceptible reaction at 82.4 0 F in the growth cabinet.

(22) - 18 and a few gay e reactions between 2 and 3.. En 1964, 256 Colombian unes and a few German oat unes were tested in the greenhouse; 8% had an infection type of 2 to 3 and 84% had a type 4. At the same time, selections from the Yugoslavian varieties Kyto and Osmo were tested and found to have a high degree of resistance to the sub-race. 6C in seedling stage It was later found that they were moderately sus-. ceptible in the intermediate stages of plant growth and resistant in the adult stage. Ninety-two F 2 unes and F 3 unes, that had as recurrent parents CI 6969 (CK-Fla/L) and ICA-BACATA, were also tested with race 6C in the greenhouse. Sorne had sufficient resistance to be included in the crossing block.. Of 312 local unes tested in 1965, 67% presented an infection type which varied from 3 to 4. The remaining unes ga y e a clear type 4 although with reduced number of pustules.. In this same period 271 varieties of Arizona were tested. The une PI 285080 gay e a type 2+ a 3- in addition to type 4- to 4+. The rernaining varieties, gay e an infection type 4+..

(23) - 19 -. Of 25 Ecuadorian unes tested under hig'n and low light intensities, 14 were completely susceptible under both conditions, and 11 were moderately susceptible.. Finaily, four irradiated varieties from Iowa showed different reactions to sub-race 6C and a few plants ga y e a type 2+ and the remainder gay e a type 3+ to 4. When grown in the field they were highly susceptible to other races prevalent in Tbaitat.. The most common reacticrL of nearly 1200 unes selected from the. segregating material in the field, was 3+ to 4; only 14 unes ga y e type 2+ to 3 in the seedling stages, and of these only 5 were moderately. resistant to moderately susceptible in the adult piant stage. The same unes were inoculated subsequently with the sub-race 3D-2. A large percentage of them were resistant or moderately resistant, especially those lines from the cross (SAC-HJ x CK/5919 - S/Mo. 811) xB, All the res istant or moderately res istant material in the greenhouse was also checked in the field. In increasing plots of ICA-BACATA, 28 plants were selected for resistance. These lines were harvested and.

(24) - 20 grown in the greenhouses for further testing Nine of the 28 had a high degree of resistance to the sub-race 3D-2 This material is being used. by the oat breeding programa The same material was tested with sub-race 6C and ga y e essentially. the same results obtained with ICA-BACATA, Le., a reaction of 2+ to 3 Most of the plants from the 28 Unes when tested in the adult stage, showed resistance. A similar situation occurred when 21 F 1 plants selected in the field were testech Approximately 507, resulted resistant or moderately resistant in the seedling stage and 35% were moderately resistant to moderately susceptible in the adult stage In 1966, on1y the seeetions Kyto and Osmo from the IORN showed resistance. The rest of the varieties were susceptible or moderately susceptible to the sub-race 6C in the seedling stage as well as in the. adult stage A few varieties of the IORN were resistant to the sub-race 3D-2.. Two varieties from Puerto Rico and two from Germany were completely susceptible to both sub-races in the various stages of plant development..

(25) - 21 -. 3). Influence of environmental conditions.. An experiment was made for two consecutive years to determine the influ-. ence of environmental conditions in the development of the oat stem rust.. Inoculated plants were exposed to natural conditions for different periods of time (7 AM to 5 PM and from 5 PM to 7AM); controls were placed directly in moist chambers after inoculation Check plants showed more infection then the exposed plants.. Plants exposed during the night were more heavily. infected than those exposed during the day0 Great differences in infection were observed from one month to another. The lowest amount of infection. occurred in February probably de to the lower outside temperatures; in general, during months with high humidity and rain the infection was higher. indicating the influence of these factors on germination and penetration of. the spores of the fungus. 4). The effect of the jg]' light intensity on the reaction of oat stem rust. In 1963 the differential variety Minrus showed an infection type 2+.. This reaction in Colombia was observed during rainy and cloudy days, but.

(26) - 22 -. during sunny and bright days Minrus ga y e type 3 reaction. On the basis of variability to light shown by the differential Minrus, sorne experiments were planned to dernonstrate the sensitivity of sorne oat varieties with gene D to light intensity. Sorne differences were noted when the seedlings were exposed to 1000 ft.c., 3500 ft.c. and 10,000 ft.c. in the greenhouse and in the field, (Fig.4). Exposition at first two 10w lurninjc intensities gay e an infection type 2+, but this type changed to 3,3++ under high light intensity. This variation was more notable in the field, due probably to higher amounts of radiation from the sun. This gene sensitivity to light could be explained by the iriteraction of host-parasite and environment. Further tests, in greenhouses with temperature controlled partially by "Floral Breeze" showed that the varieties with gene "D' t sueh as Minrus, Ag 313 and Burnett, were light sensitive. In this same test Saia was very unstable in its reactions; it showed infection type 0,1 at low intensity and X at high light intensity; Jostrain (gene E) did also. The differentials Richland (gene A), Rodney (gene B) and N. Garry (gene AB) did nót show any effect due to light intensity..

(27) - 23 -. -. 00o 9c. j,. 3,5QOf.c - Loc14LJ7r.. Figure 4. Reactiones of Minrus to Puccinia graniinis avenae Culture No. 3645 at light intensíties of about 1,000 and 3,500 footcandles at an ambient temperature of 20 0C. in 2 phytotons. fle plants received ]Jght for 14 hours per day for 16 days..

(28) - 24 Due to the influence of iight on gene "D I', it was important to know the most critical period during the infection development and also the time necessary to break resistance at different light intensities. In this experiment Che varieties Minrs, Ada and Burnett were exposed at two light intensities (1000 and 4000 ft.c.) for 14 hours daily. Sorne plants rernained permanently at 1000 ftc., and other were transferred for different periods to 4,000 f.c. Plants exposed to high light intensity after the eighth day changed the infection type from 2+ to 3-3+, 4-. This reaction was constant until the 12 day when it decreased from 4 to 2+. Varieties Kherson sel.22, Eagle 2 x C.I. 4023, and Eagle 2 x C.I. 7438 with gene F showed small differences at Che two intensities. These unes were considered to be light sensitive. The previous results were confirmed with the same varieties in 1965. (Fig. 5 and 6). Saia changed from 0;,1 to X when passed frorn 1000 ft.c. Co 3,500 ft.c..

(29) 1 3 5 7 9 11 x z1s z w 1. 23 25 27 12345. 67. S 9 1011 12 13 14 15. DAYS AFTER INOCULAT ION Figo Ltt eposition of oot seedtings aft.r inocuLation with Puccinio 9L!ifl i OVeflas. Cantiriuous lino indicates the Ught stpostion to 3,500 f. c. of contiriuous Light asid the dotted Lino zpositlon to 1,000 f.c. 14 hours por day..

(30) 1.•. •. 4.,.. ,•,. ,/. e. _ .. 26. g. 3+ Ui. 3z o u IIz. '1 p.i lo 4,190 L c. ter tws dele -. -. 1. -. o. 1. 2 3 4. 5. 6 7 e. 9. -. -. f.sr ••ala-. 10 11 12 13 14 15 16. DAYS AFTER INOCULATON. 9g.O Incre ose in the infections type according to the exposition days to Light. Alt material (gene D ) was kept at the ¡ame t.n.roture (70 9 F.). The figures on the circLes correspond to ths treotment number..

(31) 28. t-. similar conditions; from these, 18 showed a MR-MS reaction and the rest were discarded.. Later 320 unes selected in the greenhouse in 1962 and 1963 and 350 unes from Iowa were included. This material showed a reaction of moderate. resistance; sorne varieties such as: Sae HJ 94-91-10-1 (CL-6531), CL2 ARK x D69/B-HJ/Vi (C.I. 7144), C.I. 3031 x Brt (554-255) were included in the crossing block.. In 1964, unes of F 2 , F 39 F4 , and F 5 generations selected in 1961, and F1 , F 2 and F3 unes selected in 1963 in the greenhouse were tested for resistance in the field. Only 10% of the F5 material was selected for resistance, and 14 out of the 15 F 4 lines, previously tested in the greenhouse to the subrace 6C, were selected on the basis of its TT MR_MS IT reaction, The majority of the unes harvested in 1961 were susceptible and presented a high percentage of lodging; on the contrary, unes from the greenhouse which had a ' I R to MS" reaction gay e a R-MR reaction and did nct lodge0 At this time many Unes with a "resistant to moderately resistant" reaction were eliminated due to undesirable agronomic characteristics,.

(32) - 29 In 1965, 95 F 6 unes and 64 F 5 unes were discarded due to their susceptibility to stem rust; but 670 resistant plants were selected from 446 F 4 and 520 from 300 F 3 Unes. The selected material belonged to the foliowing crosses: (Sac-HJ x CK/5919 - S/Mo 811) x Sac/HJ x 6969; Sae HJ - 6969 x KH; (Sae HJ x CK/5919 - S/Mo 811) x BT/SF-6969; (Sac-HJ x CK/5919 - S/Mo 811) x LMHJ-A; Bct x Bt/SF-6969; (Wg-Srg x Vgn2 - B/Flg) Srg x R; Bct x S; and Bct x 6969 From 22 F 2 unes, 31 plants were selected in the field. Outstanding crosses in this generation were: LMHJ - CL x Bct2; Huil x Bct 2 ; and 2 Un x Bct..

(33) - 30 Five out of 25 promising varieties, tested in the fieid at Tibaitat and Surbat, showed good agronomic characters and moderate resistance; they were: (Lee/V - Fw x CL 2 x SF) x SL/L - LMHJ 98 - 4t - 3t (Sae - HJ x CK/5919 - S/Mo 811) 45 - 5b - 3t - 3t; (Sae - HJ x CK/5919 - S/Mo 811) 45 - 2b - it - it; R x (Sac - HJ x CK/5919 - S INo 811) 1372 - 2t - 4t; and Sac/HJ - 6969 x Huil 1406 - 3t - it. From these, two were discarded; the others are being tested at the present time in smali plots at Tibaitatá and Surbat. In 1966, from 671 F 5 unes, 2068 plants were selected; 908 from 517 F 4 unes, and 148 from 31 F3 unes. From the crossing block, 34 eariy.

(34) - 31 •. unes were selected and 44 discarded,. •. 2. Shade experiments.. In an experiment where light intensity was decreased to 20%, 507. and 80% using saran material, it was observed that the most light sensitive. variety was Sala; the rest of the varieties including Minrus and Burnett,. did not show any significant differences. In later experiments, the same results were obtained,. 3. Evaluation of fungicides. Initially, the fungicides Maneb and Maneb plus nickel sulphate were used. The applications were started 60 days after seeding and were repeated every 10 days, The results showed significant differences between treated plots and untreated plots.. Repeated tests using several treatrnents (timing and number of appiications) again ga y e highly significant differences between treatments, particularly in grain yield; sorne varieties yielded 307. higher. Better rust control and higher yield with any of the fungicides were obtained when spraying 60 days after seeding than at 70 or 90 days after seeding -. (Table 8)..

(35) Table 8.- CONTROL OF RUST BY USE OF FJNGICIDES AT TIBAITATA. F U N G I CIDES. OF THE APLICATIONS. MAI'EB + NICKEL SULFATE. M A N E B. INITIATION. --. ATTACK OF P. GRAMINIS AVENAE. PRODUCTION OF GRAIN KILOGRANS/HECTARE. IC.A BACATA Cl 6969. ICA BACATA ci 6969 ICA BACATA CI 6969. ATTACK OF P. GRAMINIS AVENAE. PRODUCTON OF GRAIN KILOGRANS/HECTABE. IÇA BACATA CI 6969. 60 days. 45S. 50S. 14192. 3307. 145s. 80s. 4192. 28146. 75 days. 6os. 8s. 3961. 2692. 6s. 90S. 3192. 2538. 90 days. 65S. 75S. 3269. 23146. 70S. 90S. 3038. 2115. Check. 80s. 90S. 2730. 2076. 80s. 90S. 2730. 2076. I\).

(36) - 33 Further tests including more fungicides and other locality ga y e also significant differences between sprayed and unsprayed plots. Yield was increased three times with sorne fungicides. (Table 9). 4. Small plots Sorne rust resistant unes or varieties showed high grain yield, such as: 1.. Sac-HJ x 6969, 46-5t-2t-5t-(24t)............. 5183 Kgs/Ha,. 2. Sac-HJ x 6969 46-5t-2t--5t(2t). ,... 4802 Kgs/Ha.. 3. Sac-HJ x 6969 46-5t-2t-4t(41t). ..,..... 4234 Kgs/Ha.. The aboy e three selections have shown resistance to subrace 3D-2 and moderate resistance to 6C under greenhouse conditions. The selections R-Sac HJ x CK/5919-S/Mo 811 and Sac-HJ x 6969 were outstanding at Surbat. The last one behaved as the best in Narif'io,.

(37) - 34 Table 9.- CONTROL OF RUST BY USE OF FUNGICIDES AT TIBAITATA AND "LA SELVA". Prod, Kgs/Ha.. Fungicides. % Infect.. La Selva. Tibaitatá. 2170. 4330. 52. Trifenil Acetato. 1836. 3511. 58. Trifenil Tinhidroxide, 20WP. 2012. 3010. 51. Tetrachloroisaphthalonitrile. 2819. 3626. 50. Maneb. 2125. 3534. 53. Maneb + Nickel sulfate. 2436. 3163. 65. 987. 910. 77. Tibaitatá. Maneb. -4-. Zinc. Testigo. Besides small plots, yield experiments were also conducted. S. International Oat Rus-L. Nursery At Tibaitatá most of the IORN material was highly susceptible to oat stem rust; only few varieties showed moderate susceptibility. 6. Regional Experiments These tests were conducted in the States of Cundinamarca, Boyacá and Nariño using 6 varieties and four replications. Diverse altitude and ecological conditions prevailed in these states. Sae HJ x 6969.

(38) - 35 -. cross had showed good results in Cundinamarca and Nariño, and ICA-Bacatá. in Boyacá.. Especial Experiments Sorne especial experiments concerning stem rust attack, fertility. with phcsphorus at leveis of 75, 150 and 300 Kls/ha as well as with gibberellic acid were made. The results indicated that none of these. factors had a high influence on the stem rust attack of the CI 6969. -. variety. Sorne experirnents were made in cooperation with the forage program to compare the seed and forage production of six varieties or unes selected as good silage varieties as ICA-BACATA. The results ga y e a negative correlation between silage production and grain production. ICA-BACATA, for exarnple, gay e the lowest production of silage, but the yield of grain was the highest. On the other hand, the variety Sheffor, had a good silage yield but a poor grain yield. Plants were harvested at the rnilk. •. stage in order to evaluate silage production. The results are shown in. (Table 10)..

(39) - 36 Table 10.- PRODUCTION OF GRAIN AND FORAGE IN TONS PER HECTARE OF SEVEN OAT VARIETIES ON LINES AT TIBAITATA, 194. Production of Forage (Ton./Ha.) Varieties or unes. 1 CA-Bacat. Creen. Production of Seed (Ton/Ha.). 48.63. 9.84. 2.61. 84.85. 18.50. 1.52. 104.92. 18.70. 0.34. 75.56. 18.82. 1,25. 108.63. 19.78. 0.31. 68,52. 13.86. LiS. 101.48. 18.36. 1.09. II-36-lt-lt-3t (P.c.1)+ C1-L x C1/L-RB II-36-lt-lt-2t (P.c.9) SF/C1 3 -LMHJ x C1-U II-1-7t-3b-5t (P.c.14) C1-L x C1/L-R/B II-36-lt-2t-4t (P.C.15) Sheffor C.I. 6941 (P.c.16) A - LxS II-5-2t-lt-4t-4t (P.c. 17) Put x LMHJ-A C.I. 7531 (P.C;18). + P.C. means "Parcela Chica" (small plot).

(40) - 37 -. Studies in Nariño, Antioguia and Puerto Rico A survey of the rust races and the influence of the presence of berberis in Nariño was made to compare the oat stem rust situation in relation with that of the Sabana of Bogotá. There are two different species of berberis in Nariño. One of them is similar to Berberis lehmanii,it varying only in certain details. The Andean species have not been studied carefully and therefore new species may be found in the future. Sorne of the berberis species are apparently resistant to the present races in Nariño. In the susceptible species, at least two different species of the genus Puccinia have been found. One of the two was morphologically similar to Puccinia graminis and the other one was different. The latter presented two different types of spores both spheric but one was unicellulate and orange colored and the other had two cells and red coffee color. When sorne of the collections of rust of berberis from Nariño were inoculated on wheat, barley, oat, orchard grass, and ryegrass an abundant.

(41) - 38 quantity of rust resulted only on oats. Only traces of rust were present in the rest of the plants. These results are difficult to understand because of the presence of many fields of wheat and barley in Nariño but not oats. The identification of races from Nariño was made using collections from wild and cultivated oats found between Pasto and Ipiales. The deterrninations showed the presence of 3 races and 6 subraces of rust (Table 11). All these subraces are virulent on Minrus and the type of infection was 4-1-a The best improved varieties of the breeding prograrn of Tibaitatá have been planted at "La Selva" in Antioquia. These varieties were selected prirnarily for resistance to P. coronata. Sorne of the highly resistant varieties at Tibaitatá such as the Sa-HJ x C.I. 6969 mentioned before were cornpletely susceptible to the prevalent races of P. coronata in that area. Sorne varieties were given to the Forage Prograrn to evaluate thern for their forage production. Such varieties were: Minhafer (C.I. 6913); V-HB x Colo (C.I. 6608), HJ Fw-Lee/V (C,I. 7401) and Putnarn x L M H J A (C.I. 7531). Minhafer, a late variety, ga y e the best production. The best varieties and unes of the prograrn were taken to Puerto Rico.

(42) Table 11. - PATHOGENIC RACES OF PUCCINIA GRAMINIS AVENAE IDENTIFIED FROM SINGLE PUSTULES COLLECTIONS AT NARIÑO ( COLOMBIA ). FRECUENCIES OF RACES AND SUB-RACES TOTAL. A. Isolates Percentages. 3 C. A. 7 B. 1. C. 12 C. 1. 5. Sub-races: Collections. 24. 2. 28. Percentages. 39,4. 3,3. 45,9 1,6 1,6. 8,2. o,. 61 100. Races: Collections. 26. 30. 5. Percentages. 42,7. 49,1. 8,2. 61 100.

(43) ts in 1964. From 800 varieties or tested unes, only 21 were resistant or moderately resistant. From the 21 selected, 6 were Colombian unes, The reaction of certain varieties was different, for instance, [CA-BACATA, moderately resistant in Colombia, was susceptible in Puerto Rico and P.I. 258731 resistant to the most virulent races from North Anerica was cornpletely susceptible in Colombia (Fig. 7).. DISCUSSION Sorne of the Colombian oat stem rust races are able to attack ah sources of resistance. Seven races and 38 subraces have been identified in Colombia; 4,6 and 13 are the most prevalent and virulent race groups. Subrace 6C, which is similar to the North American 8A under certain conditions, is the rnost Colombian pathogeaic race. All varieties from the world collection were susceptible to this race under Colombian conditions. Most of the material of the Colombian breeding program has been suceptible. Race 13 has become less prevalent in the past ears in the Savannah of Bogot. In the year 1960 it comprised 385Y<> of the total isolations,.

(44) Figure 7. Ficid reactions to oit st!rn rust in Colombia of fue oat selections P.C. (C1-L x CL-L-R/B) (left) and P.1 258735 (right)..

(45) - 42 -. 37. in 1965, and none in 1966. A similar situation has been observed for race 4. At the present time races 3 and 7 are the most prevalent; they are not as aggressive as 6 and 13, but they are quite severe on ICA-BACATA and similar genetic lines. The subraces 3D-2 and 7F-2 constitute a serious threat to the oats at the present time, because most of the material was selected for resistance to 6C. These selections, including ICA-BACATA, has the gene D as a common source of resistance, but different. genotypes. Sorne of these were found resistant to 3D-2 and 7F-2. The use of fungicides may play an important role in the production of. oat seed in Colombia, mainly applied on moderately resistant varieties.. Several products tested at Tiba-Ltatá hawshown prornised results. The results showed that light intensity has a strong influence on the syrnptom expression. Therefore, a variety with gene D or F, that presents a resistant reaction under low light intensity, is susceptible at high light intensity. The use cf uncontrolled conditions in the identification of races of P. . avenae may be a misleading factor. Thus light.

(46) - 43 -. intensity as well as temperature must be controlled in a correct procedure of race identification.. Regional tests should be emphazised to obtain more information about. the behavior of the future varieties under different ecological conditions. for the plant and the pathogen Past tests have shown that oats thrives well at low and high altitudes making possible seed production.. CONCLtJS IONS. The most striking findings during the development of this project could be summarized as foliows:. 1. Seven races and 38 subraces have been identified so far in Colombia. 2, Race 13 was the rnost abundant at the beginning of these studies. Now it has the tendency to dissappear. Race 4 and 6 have the same pattern. 3.. The most virulent races have been found from collections made on wild oats and sorne grasses.. 4.. Races 3 and 7 with infection type 4 on Minrus are the mt prevalent at the present time. The improved variety ICA-BACATA is susceptible to them..

(47) S. Most of the varieties and introduced unes have been susceptible to. many of the present races. The virulence and prevalence of sorne of them have made difficult to find good resistance 6.. Grain production could be improved with the use of fungicides. 7.. Studies on light intensity showed that determination of races has to be done under controlled conditions. Varieties with gene D and F are resistant at low light intensity and viceversa.. 8.. An improved variety, ICA-BACATA, was given to the farmers as a forage variety.. 9.. A good correlation of greenhouse and field results was found.. 5) Needs for Additional tnvestigations At the present time there is enough inforination about race popuLation. of Puccinia graminis avenae. We also know that until the present time we have been unable to make any permanent solution in order to eliminate the main problem in the cultivation of oat stem rust. The importance of finding a possible control of rust using chemicals has been meütioned. It is necessary to continue these experiments to.

(48) - 45 -. evaluate the economical aspects of rust control. Cooperative work with the breeding program should be continued to test. the resistance of new unes under different ecological conditions. The host-parasite interaction and the relationship to the environment. should be further studied. Studies about field resistance, and the behavior of wild oats in the. epidemiology of the disease are necessary. In addition, the role played. by other wild and cultivated hosts should be elucidated. There are other problems in oats besides the ones concerning the damage caused by both rusts. These problems are the presence of the diseases known as "enanismo", a virus disease, and mildew caused by Erysiphe graminis. In spite of their importance it is very little known about them making more difficult the study of the oat stem rust..

(49) PtJBLICATIONS 1.. Browning, J. A., E. Bustamante, J. Orjuela and H. D.Thurston. 1965, Efecto de la intensidad lutnnica sobre la reaccion de plantula de Avena a Puccinia, grarninis avenae. Agrie. Trop. (Bogotá) 21:47_48.. 2.. Browning, J. A., E. Bustamante, J. Orjuela and H. D. Thurston. 1964, Effects of light intensity in the reaction of oat seedlings to Puccinia graniinis avenae. Agronomy Abstracts p.62.. 3.. Browning, J. A., E. Bustamante, J. Orjuela and H. D. Thurston. 1967. The senaitivity to intense light of certain stem rust-oat seediing intereactions. Phytopathology (In preparation).. ti. Bustamante, E., C. F. Krull y R. Reyes. 1965. ICA-BACATA, una nueva variedad forrajera de avena. Agrie. Trop. (Bogota)21:271-274. 5.. Bustamante, E., Jr . Orjuela, J. A. Browning, H. D. Thurston and O. F. Krull. 1967. Pathogenic specializat.ion of oat stem rust in Colombia. (In preparation).. 6.. Krull, C.F., J. Orjuela and R. Reyes. 1963. Problemas en el mejoramiento de la avena en la región andina de Colombia. Agrie. Trop. (Bogotá, 19:,15-25.. 7.. Kruli, C.F., R. Reyes, J. Orjuela, and E. Bustamante. 1965. Importance of the 'small-uredja" reaction as an index of partial resistanee to oat stern rust in Colombia. Crop. Se¡. 5: 494-497.. 8.. Orjuela, J., H. D. Thurston and C. F. Krull. 1962. Physiologic specialization of Puccinia graminis avenae in Colombia. Plant Dis. Rptr. 46: 866-871. -. 9.. Orjuela, J., H. D. Thurston and C. F. Krull. 1963. Estabilidad y patogenia de la subraza 6C de Puccinia graminis avenae. Agrie. Trop. (Bogota)19: 123-133.. 10. Ramírez, H., J. Orjuela y P. Buritic.. 1967. Nuevas razas de Puccinia graminis avenae. Agrie. Trop. (Bogotá) (En preparación)..

(50)