GENETIC DISSECTION OF ROOT TRAITS IN BARLEY (H. VULGARE L.) IDENTIFIES MAJOR QTLS AND DOMESTICATION SIGNATURE

Root system architecture (RSA) plays a critical role in a plant’s ability to anchor in soil and efficiently uptake water and nutrients, directly influencing its productivity and stress resilience. In this study, we examined phenotypic variation in seven root traits at the seedling stage, conducted a genome-wide association study (GWAS), and identified novel quantitative trait loci (QTLs) and candidate genes using a globally diverse barley germplasm collection. Trait heritability estimates ranged from 0.70 to 0.88. Clear domestication and breeding trends were observed, particularly in seminal root number (SRN), which increased from 4.2 in wild accessions to 5.9 in landraces and 6.3 in modern cultivars. Similarly, root growth angle (RGA) expanded from 42.9° in wild types to 60.3° in cultivars. Both lateral root density and length increased through domestication, whereas average seminal root length (ARL) decreased. The GWAS identified 106 QTLs, accounting for 25% to 61% of phenotypic variation across traits. Candidate genes associated with GWAS peaks included ARABIDILLO-, WD-40-, exocyst complex component-, and serine protease-related genes for SRN; UDP-glycosyltransferase genes for RGA; and jasmonate receptor and F-box-related genes for ARL. These findings offer valuable resources for molecular biologists and breeders aiming to develop root architecture ideotypes that enhance crop adaptability to challenging environments.