HISTOCHEMICAL AND PHENOTYPIC STUDIES REVEALED THE DIVERSE NATURE OF WHEAT-YELLOW RUST INTERACTION

Abstract

Wheat stripe rust disease, produced by Puccinia striiformis f. sp. tritici (Pst), causes severe yield reduction worldwide. With the advent of modern wheat varieties, the sources of rust resistance are eroding. Hence a constant search for resistant genotypes is necessary. Thirty broad-based elite lines and landraces of wheat were characterized for their agronomic traits, assessed for the adult plant resistance against wheat stripe rust disease inside a trap nursery. Furthermore, the chemical response was assessed at cellular level. The landraces and elite lines displayed a diverse nature of host-pathogen interactions. The landrace LLR8 showed a hypersensitive response in the field. Seven genotypes were highly resistant while 07 were moderately resistant at the adult plant stage. The genotype RS1 showed maximum necrosis (2896 µm) indicating moderately resistant (10MR) under field conditions. Among resistant genotypes the number of hyphae at the infection site were less compared to the susceptible genotypes. The stripe rust fungal colonies were initially larger but with time the fungal colony size decreased, might be the result of the synchronized initiation of defense mechanism. The resistant genotypes also showed higher values for the hypersensitivity index. Multivariate discriminant analysis for agronomic traits divided the genotypes into low and high yielding groups, where nine genotypes were high yielding while twenty-one were low yielding under high yellow rust disease pressure. The genotypes like LLR8, Pirsabak-04 and RS4 displayed higher grain yield per plant and 1000-grain weight. The plant height and biological yield were good discriminators as they helped to discriminate between the 02 groups. The resistance sources such as LLR35, RS13, RS22, RS30, RS55, RS58, RS64, LLR5, LLR17, LLR33, RS1, RS10, RS43, and RS45 could be beneficial for the development of future cultivars with effective resistance. This genetic material should be utilized immediately for the disease management.