Molecular and Pathological Characterization of Slow Rusting Against Leaf Rust in Wheat (Triticum Aestivum L. em Thell)

Abstract

Rust diseases specifically leaf rust caused by Puccinia recondita. f. sp. tritic~ is globally important fungal of wheat (Triticum aestivum L. em. Theil) that is responsible for significant yield losses; up to 40% worldwide. Due to rapid change of pathogen races, single gene resistance is short lived in wheat cultivars. Alternatively, a more durable form of resistance is attributed to slow leaf rusting for which certain genotypes have been identified and characterized. Genetic studies indicate that slow rusting resistance is under polygenic control with moderately high heritability. Such resistance is controlled by a number of minor genes also referred to as adult plant resistance (APR) genes. Although I 0-12 slow rusting genes are known to be present in CIMMYT spring wheat, only two genes Lr34 and Lr46 have been characterized for slow rusting. Fifteen wheat genotypes including twelve CIMMYT entries, two elite Indian wheat cultivars i.e .. HUW 234 and HUW 468 and one known leaf rust susceptible cultivar i.e., Agra Local were included in the present study. These lines were first evaluated under field conditions for disease severity %, latent period and incubation period. Then, evaluated under controlled laboratory conditions where, a detached leaf assay techniques was employed with three virulent pathotypes. In the present study, we used 29R45 (12-5), 121 R63-1 (77- 5) and 21 R55 (I 04-2) pathotypes to screen all the fifteen wheat lines under controlled conditions as well as field conditions for characterizing the effect of different slow rusting genes /their combinations on leaf rust resistance. Genotypes, G-5, G-Il, G-12 and G-13 showed least disease severity, were very close to near immunity and showed comparatively a higher level of resistance against all the three pathotypes. In addition. ten tightly linked microsatellite markers were also used to characterize all the fifteen genotypes for the presence of different slow rusting/durable rust resistance genes. This was an indirect selection for desirable allele, to exploit the advantages of the durability of slow rusting and to develop a bener understanding about its mechanism that might be of much promising in the development of durable rust resistant cultivars.