INHERITANCE OF RESISTANCE TO BUNT, TILLETIA TRITICI, IN SHERMAN AND OR0 WHEAT HYBRIDS. FRED N. BRIGGS University of California, Davis, Calgornia

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1 ~ ~ IHERITACE OF RESISTACE TO BUT, TILLETIA TRITICI, I SHERMA AD OR0 WHEAT HYBRIDS FRED. BRIGGS University of California, Davis, Calgornia Received Marc 8, 19 ITRODUCTIO In previous publications, te ineritance of resistance to bunt, TiCZetia tritici (Bjerk) Wint., in ybrids wit eigt resistant varieties of weat, as been reported. Te resistance of Martin (BRIGGS 1926), Wite Odessa (BRIGGS 190b), Banner Berkeley (BRIGGS ), and Odessa (BRIGGS 1) weat varieties as been sown to result fro te sae doinant factor in eac case. Tis factor as been designated as te Martin factor (M). Hussar weat (BRIGGS 1926, 190a) depends on two factors for its resistance, te Martin and Hussar (R) factors. Tis second factor is not copletely doinant, as bunt occurs on a part of te eterozygous plants. Selections 1418 and 140 eac ave only te Hussar factor. Turkey 1558 and Turkey 055 (BRIGGS a) eac ave a single factor for resistance to tis disease wic as been designated as te Turkey factor (T). Tis factor is siilar to te Hussar factor in effect. Data are presented ere to sow te nuber of factors for resistance to bunt in Seran and Or0 weats. Te crosses necessary for identifying tese factors are available. METHODS AD MATERIALS Te parental varieties and ybrid populations were grown in te field at te University Far, Davis, California. Te etod of andling and te source of inoculu ave been described in a nuber of te publications referred to above. A single collection of bunt as been propagated and used continuously since TABLE 1 Annual percentages of bunt infection at Davis, California in te parent weal varieties during te years indicated. VARIETY Oro Seran Martin Turkey 055 Baart Wite Federation PERCETAGE OF BUTED PLATS AVERAGE _ o O GEETICS 19: 7 Ja 194

2 74 FRED. BRIGGS Seed of Seran and Oro were supplied in 1928 by Dr. K. S. QUISE- BERRY, Division of Cereal Crops and Diseases, UITED STATES DEPART- MET OF AGRICULTURE. Tese varieties were known by Dr. QUISEBERRY to be resistant to bunt. Te record of tese varieties at Davis ay be seen in table 1. Duplicate rod rows of Seran and Or0 were grown in 1929 and 190. Four rod rows of eac were grown in and 20 rod rows in. One plant of Seran and two of Or0 becae infected in. Copared wit tese resistant varieties, Baart and Wite Federation ay be considered copletely susceptible. Seran and Oro eac were crossed wit Baart to deterine te nuber of bunt-resistaqt factors in eac of tese two resistant varieties. Crosses also were ade wit Martin and Turkey 055 to test for te presence of te Martin and Turkey factor respectively. Te cross wit Selection 140, wic is te tester for te Hussar factor, was not obtained because of te difference in eading dates. As will be seen later, tis cross was not necessary for identifying te resistant factors in Oro and Seran weats. TABLE 2 Percentage of bunted plants in te parents and Fz of te crosses naed. Grown at Davis, Cdijornia. PARET OR CROSS YEAR OROW PLATS QROW UMBER UMBBR PLATS BUTED PERCET Seran Oro Turkey 055 Martin Baart SeranXBaart Seran X Turkey 055 MartinX Seran Oro X Baart OroxTurkey 055 MartinXOro o

3 BUT I WHEAT HYBRIDS 75 EXPERIMETAL RESULTS F1 seeds were not inoculated because of te sall nuber available. Were Fz plants were being grown as a source of seed to be inoculated in Fa, tey were kept free fro bunt. By doing tis, tere was no eliination of susceptible progeny by bunt in Fz. Fz data do not perit a satisfactory Mendelian analysis because soe susceptible plants usually escape infection, and resistant and eterozygous plants ay be infected occasionally. An Fz population was inoculated te year previous to growing te F and anoter population te sae year as te F. Tese data are of value because tey give soe indication of te nuber of factors by wic te resistant and susceptible varieties differ. Also tey indicate te percentage of bunt to expect in F rows of te sae genotype. Terefore, te Fz data are given in table 2. In, te percentages of bunt in te parent varieties, as well as in te Fz populations were only about alf tose secured in. In fact, te infection in was te lowest obtained during te 1 years tat records ave been available ere. Tat a nuber of susceptible Fz plants escaped infection in ay be seen fro te fact tat te Fz of SeranXBaart ad 14.4 percent of bunted plants tat year and 27.0 percent in. Siilar results were secured wit te oter crosses. Te classification of Fz plants on te basis of bunt obtained in F rows is uc ore satisfactory. F rows contained fro 0 to 70 plants, usually about 50. Tese data ay be seen in table. Te rows in te 0-5 percent class for bunt infection were subdivided into tose witout bunt and tose wit 1-5 percent because te forer group always is of interest. Te ybrids wit Seran ay be considered first. Te distribution of rows in te Seran X Baart cross is sown in figure 1. Tis curve resebles te Martin curves previously publised (BRIGGS 1926, 190b,, b). Te nuber of rows under te tree odes agrees satisfactorily wit te 1 :2: 1 ratio. Accepting 7.5 and 52.5 as inia, tere are 54.5 resistant, eterozygous and 70 susceptible rows were , 15.5, and were te nubers expected. Tis gives a value of P greater tan 0.1. Te eterozygous F rows, wic are of te sae genotype as te FZ population, averaged 24.2 percent of bunt copared wit 27.0 percent for te Fz grown in te sae nursery. Te susceptible rows ad 82.2 percent of diseased plants under te sae conditions tat Baart produced 87.0 percent. Te data ten indicate tat Seran differs fro Baart in one ajor factor for resistance to bunt. Tis factor is siilar to te Martin factor in effect. Te identity of te factor in Seran is establised by te cross wit

4 76 FRED. BRIGGS 4 - O O 00 - r- " *\o 0 w* - $: o\ vi a s r (.-( W a- - vir- *"

5 BUT I WHEAT HYBRIDS 77 Martin. Te fact tat tese ybrids did not segregate for bunt resistance sows tat Seran is identical wit Martin in its resistance to tis fungus. Te cross of Seran wit Turkey 055 ay be considered briefly even toug it did not appen to be necessary for establising te identityof te resistant factor in Seran. It was ade for tat purpose at te sae tie te oter crosses were ade. As would be expected in te ligt of te above data, tis cross gave a segregation typical of tose obtained previously wit two factors (BRIGGS 1926, 190a). In suc a cross, te susceptible rows are te only ones tat can be recognized readily. Tere were 4 FIGURE 1.-Distribution BU7 /F CiW@ur cud) of Fa rows of SeranXBaart into 5 percent classes for bunt infection. susceptible rows were 8.8 were expected, tus giving te value for P between 0.1 and 0.2. Considering now te crosses wit Oro it is interesting to copare tese wit te Seran crosses. As will be seen presently, tese two varieties depend on different genetic factors for teir resistance to bunt. Te OroX Baart ybrids gave a onoybrid ratio as sown by figure 2. Tere were 84.5 resistant, 148 eterozygous, and 64 susceptible F rows were 74.25, and respectively were te nubers expected, giving P a value greater tan 0.2. Te Fz of Or0 XBaart ad an average of 2. percent of bunt copared wit 1.4 percent for te eterozygous Ft rows. Tis is 7.2 percent ore tan found on te eterozygous rows of SeranX Baart, indicating tat soe eterozygous plants becoe infected.

6 78 FRED. BRIGGS Te susceptible rows of OroXBaart ad an average of 71.4 percent of bunt wic is lower tan produced by Baart. Tis does not appear to be 0 p tl 28 P6 24 P.? M /ff P T I 1 I I l l I I I FIGURE 2.-Distribution BUT /FECT/O fp& cenf l of F rows of OroXBaart into 5 percent classes for bunt infection PO p 18 & 16 s /I B $ /P P IO P OPY 75 /P5 175 PP P Z5 5P5 75 6P5 675 It P5 B BUM7 /f CT/O/Prr csnf/ FIGURE.-Distribution of Fa rows of MartinXOro (broken line) and SeranXTurkey 055 (solid line) into 5 percent classes for bunt infection.

7 BUT I WHEAT HYBRIDS 79 due to place effect in te nursery because te rows of Baart grown witin te sae area ad percentages of bunt about average for tat variety. Te reasons for te lower percentage of bunt for te F rows are not known. It ay be due in part at least to odifying factors. Te Oro XBaart curve is distinctly different fro te Seran XBaart curve wic is typical for te Martin factor. It is siilar, owever, to te curve resulting fro te Hussar factor (BRIGGS 190a) and te Turkey factor (BRIGGS a). Tat te Turkey factor, but not te Hussar factor, is responsible for te resistance of Or0 is sown by te Turkey 055 XOro cross. o susceptible rows were found in a population of 17 rows. Tis cross averaged 1. percent of bunt wic is sligtly ore tan te average of te parents. Oro was crossed wit Martin at te tie te oter crosses were ade. Tis was not a critical cross for identifying te bunt resistant factor in Oro. However, it is interesting to copare it wit te SeranXTurkey 055 cross because te sae two bunt resistant factors are involved in eac cross but contributed in eac case by different varieties. Tis coparison ay best be ade by referring to figure. Tese curves are very siilar considering te relatively sall nuber of rows grown fro eac cross. DISCUSSIO AD SUMMARY Data were presented to sow tat Seran and Oro differ fro te susceptible variety, Baart, in one ajor factor for resistance to bunt. Te factor in Seran was identified as te Martin factor and te one in Or0 as te Turkey factor. Tis akes ten varieties tat ave been studied. Te genetic constitution of tese as regards bunt resistance ay be seen in table 4. TABLE 4 Te genetic constitution of ten bunt resistant varieties of weat as deterined by te autor. VARIBTY Martin Wite Odessa Banner Berkeley Odessa Seran Hussar Selection 1418 and 140 Turkey 1558 Turkey 055 Oro RUT lusistaw7 FACTORB MM tt U U U 16 U U Li U U I< U (1 MM HH tt HH tt TT U U U LL U (1 Te first five varieties depend on te Martin factor, M, for teir resistance to bunt. Hussar as te Hussar factor, H, in addition to te M factor. Selections 1418 and 140 wic are fro HussarXHard Federation only

8 80 FRED. BRIGGS ave te H factor. Te last tree varieties, Turkey 1558, Turkey 055, and Or0 eac ave te Turkey factor, T, only. It is entirely possible tat in soe of tese varieties tere are oter factors for resistance to bunt wic are not apparent in te presence of te collection of bunt used in tese experients. If te M factor discovered in Martin, Wite Odessa, Banner Berkeley, Odessa, and Seran is te only factor for resistance to bunt in tese varieties, tey sould react te sae to eac collection of bunt. If soe oter resistant factor is present in one or ore, but not in all five varieties, a differential reaction sould be obtained wit soe collections. Furterore, Hussar sould be resistant to all collections to wic Martin is resistant but in addition sould be resistant to soe wic attack Martin, because of te presence of H. Finally, if te above analysis is correct, only tree differential osts are available in te above list of varieties. Oter resistant factors undoubtedly exist in oter varieties. Recently, CHURCHWARD (, ) as publised data to sow tat Florence differs fro susceptible varieties in a single recessive factor. Tis factor ust be different ten fro any of te tree listed above. Te predictions ade above ay be tested out in so far as dataare available. REED (1928), GAIES (1928), and BRESSMA () ave studied te reaction of soe of te above varieties to a nuber of collections of bunt. In general, teir results agree wit te genetic interpretation given in table 4. Considering REED S results first, coparisons are available for Martin, Odessa, and Hussar. He used two strains of Turkey wic were different fro eac oter. Since teir relation to te above strains of Turkey is not known, tey will not be considered. Tere is one outstanding difference in te infection of Martin and Odessa by one collection of bunt. Te collection of Tilletia tritici fro West Seneca, ew York, produced 54 percent of bunt on Odessa but only an average of 7 percent on Martin. Tis sae collection produced 8 percent on Hussar 527, and 2 percent on Hussar 814. Tis suggests te presence of a factor for resistance to bunt in Martin wic is not present in Odessa or peraps Hussar weats. In no oter case is Martin resistant to a collection wic readily infects Odessa or Hussar. As igt be expected, e found a case in wic Hussar was resistant but Martin and Odessa susceptible. Hussar s resistance ere ay be attributed to te H factor. GAIES (1928) reported one case were 2 percent of Wite Odessa plants were infected but only 1 percent of Martin and 1 percent of Hussar plants sowed te disease. Oterwise is data confor to tose of REED. BRESSMA () inoculated a nuber of resistant varieties wit various collections of bunt. He states: Wite Odessa, Martin, Banner Berkeley, and Regal gave results siilar to tose obtained wit Albit.

9 BUT I WHEAT HYBRIDS 81 Regal and Albit ave not been studied by te autor. However, Albit ay be assued to ave only te M factor for resistance because it is a selection fro Hybrid 128 XWite Odessa ade by GAIES at WASHIGTO STATE COLLEGE (CLARK, PARKER and WALDRO 1927). Hybrid 128 is very susceptible and probably contributed noting to te resistance of Albit. A few cases were found were soe one of tese varieties appeared to be susceptible wile te oters were resistant. For exaple, collection 7c produced 26 percent of bunt on Wite Odessa in 1928 and only percent on Martin and 1 percent on Banner Berkeley. Te following year at Corvallis tese varieties ad 0,, and 6 percent respectively, indicating tat Wite Odessa probably is resistant to tis collection. Oter siilar cases were encountered. Results at Corvallis in 1929 ade possible a coparison of Albit and Hussar in teir reaction to all 94 collections of bunt. In a nuber of cases, Hussar is resistant to collections but Albit is susceptible. Hussar s resistance again ay be attributed to te H factor. In every instance, wit te possible exception of collection 4, if Hussar is susceptible Albit also is susceptible. BRESSMA uses te results wit collection 4 at Corvallis 1929 as a type for is pysiologic for 11, presuably because Hussar produced 20 percent of bunt, wile Albit ad 6 percent, Ridit 4 percent, and Or0 percent. However, te year before, Albit ad 12.5 percent of bunt and Hussar ad 1.5 percent. If te assuption tat Albit as only te Martin factor for resistance is correct, ten tree of te four varieties finally cosen by BRESSMA as differential osts eac ave a different genetic constitution as seen in table 4. Albit, Hussar, Oro, and Ridit were te varieties used by i. Ridit is different fro te oter tree varieties in its reaction to tese collections of bunt. Te genetic constitution of Ridit is not known at present, but soeting is known about te genetics of its parents. Tis variety was selected by GAIES at WASHIGTO STATE COLLEGE fro a cross of Turkey wit Florence (CLARK, LOVE and PARKER, 1926). As pointed out earlier, CHURCHWARD (, ) believes tat te resistance of Florence is due to a single recessive factor. Te writer as sown tat te resistance of Turkey depends on te T factor. Ridit ten ay be assued to ave eiter one or bot of tese factors. In tis connection, a coparison of te reaction of Ridit to te various collections of bunt wit tat of Or0 is of interest. Oro is known to ave only te T factor. Forty-tree coparisons are available fro BRESSMA S data. Oro is resistant to 42 of tese collections, and Ridit is also resistant to tese sae collections. Tis ay be attributed to te T factor. However, Or0 is susceptible to collection 28, but Ridit is resistant to it. Ridit s resistance to tis collettion ay be

10 82 FRED. BRICGS attributed, for te purpose of tis discussion, to te factor inerited fro Florence. Recently, SMITH () as differentiated tree pysiologic races of bunt by te reaction of Martin. Martin was resistant to T1, gave 19 percent of bunted eads wit T2, and 71 percent wit T. Furterore, bunted eads resulting fro T2 ad very sall sut balls. BRESSMA () reported a few abnoralities wit soe of is collections. Te reaction of Martin to te above tree fors of bunt is not readily explained on te basis of a single factor. It is entirely possible tat te difference in reaction to T1 and T2 ay be due to a odifying factor. Fro te above discussion, it is apparent tat a genetic analysis of oter resistant varieties is desirable. Also ore data are needed on te pysiologic races of tis disease. Pure lines of te fungus are igly desirable in tis connection. BRESSMA () found tat soe of te collections of bunt received by i were a ixture of te two species of Tilletia. It sees equally certain tat soe of te collections ay ave been ixtures of pysiologic fors. Iproveents in te purity of te inoculu are being ade. LITERATURE CITED BRESSMA, E.., Varietal resistance, pysiologic specialization, and ineritance studies in bunt of weat Oregon Agric. Expt. Sta. Bull. 281: 44 p., illus. BRIGGS, FRED., 1926 Ineritance of resistance to bunt, Tilletia tritici (Bjerk) Winter, in weat. J. Agric. Res. 2: , illus. 190a Ineritance of te second Hussar factor for resistance to bunt, Tilletia tritici, in Hussar weat. J. Agric. Res. 40: , illus. 190b Ineritance of resistance to bunt, Tilletia tritici, in Wite Odessa weat. J. Agric. Res. 40: 5-59, illus. Ineritance of resistance to bunt, Tilletia tritici, in ybrids of Wite Federation and Banner Berkeley weats. J. Agric. Res. 42: 07-1, illus. a Ineritance of resistance to bunt, Tilletia tritici, in crosses of Wite Federation wit Turkey weats. J. Agric. Res, 44: , illus. b Ineritance of resistance to bunt, Tilletia tritici, in ybrids of Wite Federation and Odessa weat. J. Agric. Res. 45: , illus. CHURCHWARD, J. G., Studies in te ineritance of resistance to bunt in a cross between Florence and Hard Federation weats. Proc. Roy. Soc..S.W., 64: , illus. Ineritance of resistance to bunt, Tilletia tritici (Bjerk) Winter, and oter caracters in certain crosses of Florence weat. Proc. Linn. Soc..S.W., 57: 1-147, illus. CLARK, J. A., LOVE, H. H. and PARKER, J. H., 1926 Registration of iproved weat varieties. J. Aer. Soc. Agron. 18: CLARK, J. A., PARKER, J. H. and WALDRO, R. L., 1927 Registration of iproved weat varieties. J. Aer. Soc. Agron. 19: GAIES, E. F., 1928 ew pysiologic fors of Tilletia levis and T. tritici. Pytopatology 18: REED, G. M., 1928 Pysiologic races of bunt of weat. Aer. J. Bot. 15: SMITH, W. K., Reaction of Martin weat to tree pysiologic fors of Tilletia tritici. Pytopatology 22: , illus.