Genome-wide association mapping for grain and forage quality traits in a subtropical oat germplasm collection adapted to highland regions of Eastern Africa

Oat ( Avena sativa L.) is a globally important cereal cultivated for both livestock feed and human nutrition. However, its productivity is increasingly constrained by both biotic and abiotic stresses, exacerbated by rapid climate change. To support the development of dual-usage, stress-resilient and high-yielding cultivars adapted to subtropical agroecologies, we evaluated the genetic structure and agronomic performance of a 169-member oat association panel. This panel was phenotyped for key vegetative, forage feed quality and grain related traits across three subtropical locations in Sub-Saharan Africa (SSA) over two growing seasons and genotyped using Genotyping-by-Sequencing (GBS). Diversity analysis, based on filtered SNPs, showed moderate genetic diversity (He = 0.39 and PIC = 0.3), and population structure analysis identified two main sub-groups with varying degrees of admixture, suggesting gene flow among different groups. Genome-wide association analysis uncovered 42 SNPs significantly associated with sixteen traits (false discovery rate, FDR, <0.05), along with 46 candidate genes located near these loci. Notably, candidate genes associated with seed traits included a homolog of rice OsAK3 , encoding adenylate kinase, and a UDP-glucosyltransferase homologous to rice GSA1 , both previously shown to regulate grain size. These genes were located near QTL linked to seed length, width, and thousand-grain weight. Another key candidate, encoding a subunit of the ESCRT-II complex (VPS25), was identified near a separate QTL and is implicated in intracellular trafficking, endosperm development, and overall seed quality. By illuminating the genetic architecture of economically important traits and identifying molecular markers linked to yield, quality and resilience, this study provides valuable genomic resources to support genomics-based breeding aimed at developing climate-resilient, productive oats varieties adapted to sub-tropical agro-ecologies.