Mapping of Adult Plant Leaf Rust Resistance in Aus27506 and Validation of Underlying Loci by In-Planta Fungal Biomass Accumulation

• Main Authors: Pakeerathan Kandiah, Mumta Chhetri, Matthew Hayden, Michael Ayliffe, Harbans Bariana, Urmil Bansal
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Agronomy
• Subjects: wheat; leaf rust; QTL mapping
• Online Access: https://www.mdpi.com/2073-4395/10/7/943

Among the rust diseases, leaf rust of wheat caused by <i>Puccinia triticina</i>, is the most prevalent worldwide and causes significant yield losses. This study aimed to determine the genomic location of loci that control adult plant resistance (APR) to leaf rust in the pre-Green Revolution landrace accession, Aus27506, from the “Watkins Collection”. An Aus27506/Aus27229-derived F₇ recombinant inbred line (RIL) population was screened under field conditions across three cropping seasons and genotyped with the iSelect 90K Infinium SNP bead chip array. One quantitative trait loci (QTL) on each of the chromosomes 1BL, 2B and 2DL explained most of the leaf rust response variation in the RIL population, and these were named <i>QLr.sun-1BL</i>, <i>QLr.sun-2B</i> and <i>QLr.sun-2DL</i>, respectively. <i>QLr.sun-1BL</i> and <i>QLr.sun-2DL</i> were contributed by Aus27506. <i>QLr.sun-1BL</i> is likely <i>Lr46</i>, while <i>QLr.sun-2DL</i> appeared to be a new APR locus. The alternate parent, Aus27229, carried the putatively new APR locus <i>QLr.sun-2B.</i> The comparison of average severities among RILs carrying these QTL in different combinations indicated that <i>QLr.sun-2B</i> does not interact with either of the other two QTL; however, the combination of <i>QLr.sun-1BL</i> and <i>QLr.sun-2DL</i> reduced disease severity significantly. In planta fungal quantification assays validated these results. The RILs carrying <i>QLr.sun-1BL</i> and <i>QLr.sun-2DL</i> did not differ significantly from the parent Aus27506 in terms of resistance. Aus27506 can be used as a source of adult plant leaf rust resistance in breeding programs.