Detached leaf assay for evaluating resistance to leaf rust <em>Pst.</em> 104-2 in wheat (<em>Triticum aestivum</em> L.)

Abstract

Leaf rust (Brown rust) of wheat caused by <em>Puccinia triticina </em> Eriks. inflicts 30-50 % yield loss annually. This can be effectively curtailed by cultivating resistant varieties. In the process of resistance breeding, host resistance is evaluated by applying techniques of whole seedling assay done in glasshouse (WSAG) and/or whole plant assay in field (WPAF) which is labour intensive and vulnerable to environmental fluctuations. Here, we propose a simpler new technique of detached leaf assay (DLA) accomplished under controlled environment and standardized which could be used as an alternative method of evaluating wheat for rust resistance. Incubation and latent period which are components of partial disease resistance (PDR) imparting long lasting field life to the cultivars were enumerated after applying the WPAF, WSAG and DLA. There was close similarity of infection types obtained in DLA, WSAG and WPAF in the seven cultivars. Among the components of PDR, incubation period recorded under DLA was correlated with incubation period in WSAG and WPAF (r= 0.99 and 0.73, respectively). The latent period in DLA also showed a stronger association with latent period in WSAG and WPAF (r= 0.98 and 0.99, respectively) indicating the reliable potential of the detached leaf assay as an effective alternative or supplementary technique to the other two conventional methods in evaluating host resistance. DLA also obviates the cumbersomeness of WSAG and WPAF.