Mapping and Validation of a Novel Major QTL for Adult-Plant Stage Resistance to Stripe Rust in a Wheat Landrace ‘Xuxumai’

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a globally devastating wheat disease. The identification of novel loci for durable resistance is crucial for sustainable control of the disease. Chinese wheat landrace Xuxumai (XXM) has exhibited consistent high-level adult-plant resistance to stripe rust in China. To elucidate the genetic basis of its resistance, a recombinant inbred line (RIL) population was developed from a cross between XXM and susceptible cultivar Taichung 29. Disease severity (DS) of the parents and 149 RILs was evaluated across multiple field seasons. High-density SNP genotyping facilitated the construction of a genetic linkage map, which was used for quantitative trait locus (QTL) mapping. Three stable QTL, designated QYr.XXM-1AL, QYr.TC29-1BL, and QYr.TC29-2BS, were identified on chromosomes 1A, 1B, and 2B, respectively. Collectively, they explained up to 20.86% of the phenotypic variance. Comparative analysis indicated that QYr.XXM-1AL and QYr.TC29-1BL are likely novel loci, while QYr.TC29-2BS coincides with a known gene-rich region. RILs possessing all three QTL showed significantly lower DS (mean reduction of 50%) compared to those with 0 to 2 QTL. Furthermore, Kompetitive allele-specific PCR (KASP) markers closely linked to QYr.XXM-1A were developed and validated. This study reveals novel genetic resources for stripe rust resistance in XXM. The major QTL QYr.XXM-1A and its associated KASP markers hold substantial promise for enhancing the efficiency of marker-assisted selection in wheat breeding programs.