QTL mapping of adult-plant resistance to leaf rust based on SSR markers and SNP sequencing of Chinese wheat landrace Xu’ai (Triticum aestivum L.)

Abstract

Leaf rust (Puccinia recondite f. sp. Tritici) is the prevalent wheat (Triticum aestivum) disease in many areas of the world. The preferred method of control is to introduce resistance genes against this disease into elite wheat germplasm, an approach that is more environmentally friendly than applying fungicides and that has underpinned sustained wheat production to date. Identifying new adult-plant resistance (APR) genes and quantitative trait loci (QTL) for leaf rust resistance can expand the sources of disease resistance and contribute to breeding for durable resistance, allowing the pyramiding of multiple APR genes in elite wheat lines. In this study, simple sequence repeat (SSR) markers, together with the bulked segregant and single nucleotide polymorphism analyses (BSA and SNP), were used to identify QTL in F2:3 lines derived from Xu’ai and Zhengzhou 5389. Yield data for the population lines were used to detect QTL by inclusive composite interval mapping analysis. Six QTL were identified, namely, QLr.hebau-1BL, QLr.hebau-2AS, QLr.hebau-2BS, QLr.hebau-2BL, QLr.hebau-4B and QLr.hebau-6AL. Both QLr.hebau-2BS and QLr.hebau-4B were detected in five environments, explaining 23.1–37.5% and 7.6–18.3% of the phenotypic variation for resistance, respectively. After analysis, QLr.hebau-1BL and QLr.hebau-4B were identified as Lr46 and Lr12, respectively. QLr.hebau-2BS is very close to the temperature-sensitive gene LrZH22, but requires further detection. QLr.hebau-2AS, QLr.hebau-2BL and QLr.hebau-6AL constitute new resistance loci. These genes or QTL for reduced disease severity were derived from the resistant parent Xu’ai. The QTL identified and their flanking markers could be useful for fine mapping and marker-assisted selection (MAS).