Identification of stable QTL for yield-related traits in a durum wheat Svevo × Zavitan RIL population

Yield-component QTL mapping in a Svevo × Zavitan durum wheat RIL population identifies 11 stable loci across four environments and prioritizes 67 and 88 high-confidence candidate genes linked to grain development and regulatory pathways, providing markers and targets for yield improvement. Wheat is a cornerstone of global food security. Durum wheat (Triticum turgidum ssp. durum), domesticated from wild emmer wheat (Triticum turgidum ssp. dicoccoides), represents a valuable genetic reservoir for improvement. To decipher the genetic architecture of yield components, a population of 135 recombinant inbred lines (RILs) derived from a cross between the elite durum wheat cultivar Svevo (female) and wild emmer wheat accession Zavitan (male) was evaluated for grain length (GL), grain width (GW), grain length-width ratio (LWR), and thousand-grain weight (TGW) across four environments. Genotyping was performed using the wheat 90 K single nucleotide polymorphism (SNP) array and subsequent quantitative trait locus (QTL) analysis revealed 11 stable QTL, with physical intervals ranging from 0.7 to 15.6 Mb in the durum wheat reference genome. Among these, three QTL for GL (QGLsv.swust-5AL, QGLsv.swust-5BL, and QGLsv.swust-7AL), two for GW (QGWsv.swust-4AL and QGWsv.swust-5AL), and two for TGW (QTGWsv.swust-2BL and QTGWsv.swust-5BL) carried positive alleles from the cultivated parent Svevo. Conversely, all four QTL for LWR (QLWRzv.swust-2BS, QLWRzv.swust-4AL, QLWRzv.swust-4BL, and QLWRzv.swust-6AS) were contributed by the wild parent Zavitan. Collectively, these QTL explained 9.22% to 19.22% of the phenotypic variation. Projection of the QTL intervals onto the Chinese Spring, Svevo, and Zavitan reference genomes identified 67, 88, and 70 high-confidence candidate genes, respectively. Functional annotation associated these genes with seed development, transcription regulation, hormone signaling, ubiquitin-mediated proteolysis, and carbohydrate metabolism. This study highlight the complementary genetic contributions from both cultivated and wild gene pools. The identified QTL and candidate genes provide a direct resource for marker-assisted breeding, demonstrating the utility of interspecific crosses to enrich the genetic basis for yield enhancement in durum wheat.