Identification of novel QTL for tiller angle on chromosome 2H and 5H in barley

Tiller angle is a critical agronomic trait determining plant architecture, planting density, and grain yield in cereal crops. However, the genetic of tiller angle in barley remains largely unexplored, particularly regarding the underlying quantitative trait loci and their stability across different genetic backgrounds. In this study, we performed quantitative trait locus (QTL) mapping for tiller angle using a recombinant inbred line (RIL) population derived from a cross between cultivated barley Morex and wild barley AWCS276. Phenotypic evaluation was conducted across four trials, revealing continuous variation and high broad-sense heritability (0.93) for tiller angle. Three QTL for tiller angle were identified on chromosomes 2 H and 5 H. Among them, QTA.cdac-2 H.1 was consistently identified in all trials and best linear unbiased estimates (BLUE), explaining up to 20.1% of the phenotypic variance, while QTA.cdac-5 H was identified in three trials and BLUE, explaining up to 11.9% of the variance. Both QTL were validated in two validation populations using the linked markers Indel2H and KASP5H, confirming their stability across different genetic backgrounds. Leveraging the available genome assemblies of the two parental genotypes and gene annotation, eight candidate genes were identified for QTA.cdac-2 H.1 and QTA.cdac-5 H. These findings provide valuable molecular markers for marker-assisted selection and offer new insights into the genetic mechanisms underlying tiller angle determination in barley. The stable QTL and associated candidate genes lay a foundation for further functional characterization and breeding applications.