Assessment and genetic characterisation of stripe rust resistance at seedling and adult plant stages in bread wheat germplasm

Stripe rust or yellow rust caused by Puccinia striiformis f. sp. tritici of wheat is a major biotic stress with rapid epidemics. Host-plant resistance is one of major breeding strategies in development of resistant cultivars, wheat germplasm showing great genetic diversity for resistance was screened for identifying potential resources for major and minor resistance genes. Forty-seven germplasms of advanced breeding materials were selected and seedling reaction test was conducted on germplasm to know potential race specific resistance against Pst stripe rust races. Relative susceptibility index assessed based on seedling infection type and their numerical response values. Adult plant screening under natural epiphytotic conditions recorded different quantitative disease parameter values viz., area under the disease progress curve (AUDPC), average coefficient of infection (ACI) and relative resistance index (RRI) which helps in categorising germplasm into durable non-specific ones. The phenotypic assessment of germplasm which was categorised as resistant germplasm, was validated through simple sequence repeat (SSR) markers for Yr race specific genes such as Yr5, YR10 and Yr15 using different SSR markers viz., Xgmw501, Brac349, Xpsp300, Xgmw273 and Gms413. The gene Yr5 was postulated in 14 germplasm lines, Yr15 in 14 germplasm lines and Yr10 in 11 germplasm lines. Four germplasm postulated with Yr5+Yr15, six germplasm postulated with Yr15+Yr10 and Yr5+Yr10 postulated in three germplasm and two germplasm showed immune response with other race specific resistance.