Dissecting the genetic basis of grain weight and size in common oat by genome-wide association study

Abstract

Grain weight and size are critical traits that determine oat yield and quality yet our understanding of the genetic variability and molecular mechanisms underlying these characteristics in oat remains limited. To address this knowledge gap, we conducted an extensive study on 319 oat accessions, measuring four key grain size-related traits, including thousand grain weight (TGW), grain length (GL), grain width (GW), and grain perimeter (GP) across four field trials in Chengdu, Southwest China. Within in this panel, we uncovered highly heritable variation in the aforementioned grain trait. Modern cultivars displayed elevated mean values in TGW and GW, underscoring the impact of breeding on these traits. Hulless oats exhibited inferior grain characteristics compared to the de-hulled hulled oats. Genome-wide association study identified 18 loci that were significantly associated with these traits across multiple environments. Of them, three SNPs, S1A_17559296, S7D_305063624, and S1C_38047438 were associated with various traits. The superior alleles of these stable loci additively increased TGW and grain size, providing guidance for pyramiding breeding. Candidate genes associated with ubiquitin pathway, cell division and differentiation were identified for some of the associated SNPs. Further validation of these loci will help to understand their roles in the regulation of grain size.