Genetic diversity analysis of sorghum grain traits and development of KASP markers for grain width genes SbTGW3 and SbGS5.

A thorough assessment of phenotypic and genetic diversity in sorghum germplasm is essential for uncovering key genes and advancing crop breeding. In this study, 340 sorghum accessions were evaluated over two years in field trials, with six grain yield-related traits systematically measured. Analyses of genetic parameters, correlations, and principal components indicated that grain width (GW) exhibits high heritability and is strongly positively correlated with 1000-grain weight (TGW), while the grain length-width ratio (LWR) negatively correlates with both traits. These results highlight the importance of GW in yield enhancement and imply that increasing grain length (GL) may not benefit yield performance. Using principal component and cluster analyses, we selected 11 germplasm accessions showing high yield potential. Through haplotype-based association analysis of eight key grain size regulatory genes, we identified ten superior haplotypes significantly associated with GW and TGW. Notably, two particularly promising haplotypes, SbTGW3-hap5 and SbGS5-hap6, which have been rarely utilized in breeding, increased TGW by 27.69% and 17.85%, and GW by 8.50% and 5.70%, respectively, compared to the population mean. We developed highly efficient kompetitive allele-specific PCR (KASP) markers for these two haplotypes, which achieved 100% target genotype selection accuracy in a test of 178 materials. This study not only deepens the theoretical understanding of the genetic architecture of grain traits in sorghum but also provides critical phenotypic targets, clearly defined molecular markers, and effective KASP genotyping tools for high-yield breeding programs. Collectively, these findings establish a robust foundation for sorghum genetic improvement and molecular design breeding.