Genome-Wide Mapping of Adult Plant Resistance to Leaf Rust and Stripe Rust in CIMMYT Wheat Line Arableu#1

Abstract

Leaf (brown) rust (LR) and stripe (yellow) rust (YR), caused by <i>Puccinia triticina</i> and <i>P. striiformis</i> f. sp. <i>tritici</i>, respectively, significantly reduce wheat production worldwide. Disease-resistant wheat varieties offer farmers one of the most effective ways to manage these diseases. The common wheat (<i>Triticum aestivum</i> L.) Arableu#1, developed by the International Maize and Wheat Improvement Center and released as Deka in Ethiopia, shows susceptibility to both LR and YR at the seedling stage but a high level of adult plant resistance (APR) to the diseases in the field. We used 142 F₅ recombinant inbred lines (RILs) derived from Apav#1 × Arableu#1 to identify quantitative trait loci (QTLs) for APR to LR and YR. A total of 4,298 genotyping-by-sequencing markers were used to construct a genetic linkage map. The study identified four LR resistance QTLs and six YR resistance QTLs in the population. Among these, <i>QLr.cim-1BL.1/QYr.cim-1BL.1</i> was located in the same location as <i>Lr46/Yr29</i>, a known pleiotropic resistance gene. <i>QLr.cim-1BL.2</i> and <i>QYr.cim-1BL.2</i> were also located on wheat chromosome 1BL at 37 cM from <i>Lr46/Yr29</i> and may represent a new segment for pleiotropic resistance to both rusts. <i>QLr.cim-7BL</i> is likely <i>Lr68</i> given its association with the tightly linked molecular marker <i>cs7BLNLRR</i>. In addition, <i>QLr.cim-3DS</i>, <i>QYr.cim-2AL</i>, <i>QYr.cim-4BL</i>, <i>QYr.cim-5AL</i>, and <i>QYr.cim-7DS</i> are probably new resistance loci based on comparisons with published QTLs for resistance to LR and YR. Our results showed the diversity of minor resistance QTLs in Arableu#1 and their role in conferring near-immune levels of APR to both LR and YR, when combined with the pleiotropic APR gene <i>Lr46</i>/<i>Yr29</i>.