PHYSIOLOGICAL RACES AND VIRULENCE DIVERSITY OF PUCCINIA GRAMINIS PERS. F. SP. TRITICI ERIKS. & E. HENN. DURING 2011/2012 AND 2012/2013 GROWING SEASONS IN EGYPT

Document Type : Original Article

Authors

Wheat Dis. Res. Division, Plant Path. Res. Inst., ARC, Giza, Egypt.

Abstract

Stem rust of wheat caused by Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn., is the most destructive disease of wheat worldwide as well as in Egypt. It can causes high sever losses of wheat crops over wide areas during epidemic years. Hence, this study was carried out to detect the virulence dynamic and diversity of P. graminis f. sp. tritici in different locations and studying the efficacy of stem rust resistant genes in Egypt seedling stage. Stem rust collections were obtained from infected wheat stems throughout the survey of wheat fields and nurseries in three locations (Sids, El Sharkia and El Nubaria) during 2011/2012 growin g season. Whereas during 2012/2013 growing season the samples collected from six locations (Giza, Sids, Tag El Aiz, Sakha, El Sharkia and El Nubaria). Based on race analysis of stem rust populations, and race determination by inoculating stem rust differential hosts, the phenotypic characterization of P. graminis f. sp. tritici during 2011/2012 growing season resulted in identification of 86 races from 22 successful samples, all of them showed 1.16% frequency. Race BBBBC was a virulent on all the tested Sr genes, except Sr MCN, whereas race TTTTK was virulent on all the tested Sr except Sr 24. On the other hand, analysis during the next growing season revealed that, 123 races with a frequency ranged from 0.81% to 2.43% were identified.  Race groups BB---, LG---, BJ---and TT--- were common at the tested locations during the two growing seasons. Regarding stem rust resistant gene efficacy during the study Sr24, Sr38 and Sr31 exhibit the highest efficacy% (95.34, 91.86 and 87.21 respectively) during the two seasons. Thus, deployment of effective Sr genes such as Sr24, Sr38 and Sr31 in single cultivar through gene pyramiding has paramount importance as the additive effects of several genes gives the cultivar a wider base stem rust resistance along with periodic race survey.

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