Molecular mapping of QTLs for stripe rust resistance in bread wheat (Triticum aestivum L.)

Stripe rust, caused by Puccinia striiformis f. sp. tritici, poses a major threat to global wheat production, adversely impacting grain yield, quality, and nutritional value. Identifying quantitative trait loci (QTLs) associated with resistance is essential for wheat breeders aiming to develop rust-resistant varieties through molecular breeding strategies. To unravel the genetic basis of resistance, a mapping population of 212 recombinant inbred lines (F₈), derived from a cross between resistant parent (W8627) and the susceptible parent (PBW343), was evaluated against the most prevalent and virulent pathotypes at both the seedling and adult plant stages over two consecutive years (2021-22 and 2022-23). The area under the disease progression curve (AUDPC) and analysis of variance revealed high variability among the RILs across both years. For QTL mapping, genotyping was conducted using a comprehensive approach that combined a 3.9 K Diversity Arrays Technology (DArT) array with SSR markers. This effort resulted in the identification of 602 DArT markers and 23 SSR markers, which were used to construct a robust integrated linkage map comprising 21 linkage groups which led to the identification of two seedling resistance QTLs, QYr.iiwbr.3BS.1 (3B) and QYr.iiwbr.6DS.1 (6D), as well as two consistent QTLs; QYr.iiwbr.2BL.1 (2B) showing the phenotypic variance of 9.67% with a LOD score 4.51 and QYr.iiwbr.6DS.2 (6D) explaining 7.33% phenotypic variance with LOD score 3.61 for adult plant resistance. Further, in silico analysis revealed putative candidate genes, including those encoding Inositol transporter-1 and protein transport protein sec16, which hold promise for future functional validation and deployment in rust resistance breeding.