Phenotyping slow leaf rusting components and validation of adult plant resistance genes in exotic wheat germplasm

‘Slow rusting’ adult plant resistance (APR) genes can provide non-specific durable resistance to leaf rust in wheat. In this study, we phenotyped 120 exotic wheat accessions for slow rusting components and investigated the presence of known APR genes. The tightly linked STS/SSR molecular markers csLV34 , Xwmc44 , Xcfd71 and csGS respectively for APR genes viz., Lr34, Lr46, Lr67 and Lr68 were used to characterize the wheat accessions. Lr46 was the most frequent (62.5%) followed by Lr67 (43.3%), Lr68 (26.6%) and Lr34 (21.6%). Wheat accessions carrying known APR genes showed a range of disease severity responses, but the severities were significantly lower (R to 60MS) than those of the susceptible checks (80S to 100S), with the exception of some lines carrying Lr46 and Lr67 alone or in combination showed disease severity up to 100S. Accessions such as EC-603897, EC-693258, EC-693262, EC-693285 and EC-693306 carried four known APR genes viz., Lr34, Lr46, Lr67 and Lr68 and provided high levels of resistance with area under disease progress curve (AUDPC) value ranging from 0 to 149.3. These genotypes will serve as useful donors for resistance breeding efforts seeking to develop wheat varieties with durable leaf rust resistance.