Identification of adult plant rust resistance genes in some pre and post-green revolution Indian bread-wheat varieties

Achieving durable resistance against wheat rust diseases is a primary goal of many wheat breeding programmes. This study aimed to characterize adult plant rust resistance in some old and new Indian bread-wheat varieties. Sixty-four bread wheat genotypes were evaluated to identify adult plant resistance (APR) to stripe rust and leaf rust during 2016-17 and 2017-18 under controlled environment. In these genotypes, APR was characterized using final disease score (FDS), average coefficient of infection (ACI), and area under disease progress curve (AUDPC). Majority of the genotypes were susceptible to moderately susceptible to stripe rust and moderately resistant to moderately susceptible to leaf rust. Leaf tip necrosis ( LTN ) and pseudo black chaff ( PBC ) were present in 41 and 33 genotypes, respectively. The three linked diagnostic molecular markers for APR genes, viz. Yr18/Lr34 , Yr46/Lr67 and Lr68 were used to characterize the test genotypes and interestingly, 39 genotypes possessed at least one of the three resistance genes. None of the genotypes carried all the three genes. Lr68 was present in the highest frequency. Pre-green revolution tall Indian bread-wheat varieties, viz. NP101, NP836, NP850, NP856, NP876, and NP880 showed the presence of both Yr46/Lr67 and Lr68 , whereas Yr18/Lr34 and Sr2/Yr30 were absent. Post-green revolution semi-dwarf wheats showed new combinations of APR with decreased frequency of Yr46/Lr67 and Lr68 genes. The results of this investigation suggest that the APR genes Yr46/Lr67 and Lr68 do not function additively.