Genetics of resistance to stem rust in five bread wheats

Five bread wheat cultivars, namely, HD 2643, HI 1077, HP 1731, UP 2338 and WH 147 were analysed against three pathotypes of Puccinia graminis f. sp. tritici i.e. 21(9G5), 40A(62G29) and 117-5(166G2- 2). The segregation pattern of seedlings in F2 derived from crosses with Agra Local as susceptible parent showed the presence of 2 dominant resistance genes in HD 2643 and WH 147, and 3 dominant resistance genes in HI 1077, HP 1731 and UP 2338 when analysed with pathotype 21(9G5). Reciprocal crosses of the cultivars also supported the above findings. Analysis of BC1 and BC2 with pathotype 40A (62G29) confirmed the presence of 2 dominant independent genes in HD 2643 and 1 dominant resistance gene each in HP 1731 and UP 2338 . The F2 seedlings of all the intercrosses of parents did not segregate for susceptibility to pathotype 21 (9G5). It appears that resistance genes are common in above cultivars. However, some of the diallele crosses showed segregation to pathotype 40A (62G29) and 117-5 (166G2-2) showing dissimilarity of resistance. Based on seedling resistance test (SRT) of the above wheats with 12 pathotypes Sr8 and Sr11 in HI 1077 and HP 1731, and Sr11 in WH 147 were postulated.