QTL mapping for leaf rust resistance in bread wheat using PBW343/W8627 RIL population

Leaf rust, caused by Puccinia triticina, inflicts 10-50% yield losses in bread wheat, with newly emerging virulent pathotypes overcoming major Lr genes and rendering the cultivars susceptible. The identification of genetic loci conferring resistance to wheat leaf rust, coupled with the development of molecular markers and the incorporation of resistant alleles into breeding programs, represents the most sustainable and cost-effective strategy for disease management.

The present study, employed a recombinant inbred line population derived from (PBW343/W8627) was utilized to map QTLs for leaf rust resistance at seedling and adult plant stages. The RIL population along with its parents was evaluated at seedling and adult plant stages against most prevalent and virulent pathotypes at seedling and adult plant stages for the two crop seasons (2021-22 and 2022-23).

Analysis of variance revealed significant differences among the RILs across years. For QTL mapping, genotyping was conducted using 3.9K DArT SNPs leading to the identification of two QTLs: QLr.iiwbr.2B.1 (2B) explaining phenotypic variance of 13.26% with a LOD score 8 and QLr.iiwbr.5B.1 (5B) explaining 14.91% with LOD score 3.91 for all stage resistance (ASR) as well as one QTL for adult plant resistance (APR), QLr.iiwbr.6B.1 (PVE 14.21%). Further, in silico analysis revealed a putative candidate gene encoding for Annexin (TraesCS5B02G201700) which plays an important role in disease resistance in wheat.

The study identified new QTLs associated with leaf rust resistance, providing valuable sources to accelerate the development of durable rust resistant sources. Further, characterization of these QTLs will strengthen their utility in rust resistance breeding.