QTL Mapping of Adult-Plant Resistance to Leaf and Stripe Rust in Wheat Cross SW 8588/Thatcher using the Wheat 55K SNP Array

Abstract

Wheat leaf rust (caused by <i>Puccinia triticina</i>) and stripe rust (caused by <i>Puccinia striiformis</i> f. sp. <i>tritici</i>) cause large production losses in many regions of the world. The objective of this study was to identify quantitative trait loci (QTL) for resistance to leaf rust and stripe rust in a recombinant inbred line population derived from a cross between wheat cultivars SW 8588 and Thatcher. The population and parents were genotyped with the Wheat 55K SNP Array and SSR markers and phenotyped for leaf rust severity at Zhoukou in Henan Province and Baoding in Hebei Province. Stripe rust responses were also evaluated at Chengdu in Sichuan Province, and at Baoding. Seven and six QTL were detected for resistance to leaf rust and stripe rust, respectively. Four QTL on chromosomes 1BL, 2AS, 5AL, and 7BL conferred resistance to both rusts. The QTL on 1BL and 2AS were identified as <i>Lr46</i>/<i>Yr29</i> and <i>Lr37</i>/<i>Yr17</i>, respectively. <i>QLr.hebau-2DS</i> from Thatcher, identified as <i>Lr22b</i> that was previously thought to be ineffective in China, contributed a large effect for leaf rust resistance. <i>QLr</i>.<i>hebau-5AL</i>/<i>QYr.hebau-5AL</i>, <i>QLr.hebau-3BL</i>, <i>QLr.hebau-6DS</i>, <i>QYr.hebau-4BS</i>, and <i>QYr.hebau-6DS</i> are likely to be new QTL, but require further validation. Kompetitive allele-specific PCR (KASP) markers for <i>QLr.hebau-2DS</i> and <i>QLr.hebau-5AL</i>/<i>QYr.hebau-5AL</i> were successfully developed and validated in a diverse wheat panel from Sichuan Province, indicating their usefulness under different genetic backgrounds. These QTL and their closely linked SNP and SSR markers will be useful for fine mapping, candidate gene discovery, and marker-assisted selection in breeding for durable resistance to both leaf and stripe rusts.