Genome-Wide Association Study of Genes Conferring Tiller Number in Rice Region of South-China

Rice tiller number is a key determinant of panicle number and yield, yet its genetic architecture is highly influenced by environmental variation. Identifying loci showing reproducible effects across multiple growing seasons at the same experimental site is important for improving the reliability of GWAS-based locus prioritization for breeding. In this study, 240 rice accessions from the Rice3K panel were evaluated for tiller number over three growing seasons (2021–2023) in Sanya, Hainan Province, representing the South China rice-growing region. Genome-wide association analyses using GLM and MLM, combined with BLUEs, identified reproducible genetic signals. Several previously reported tillering-related genes, such as NAL1, BON3, ANT1, MRG702, D27, WTG1, and VPE2, were detected across different analyses. Among them, NAL1 and ANT1 represented the most consistently associated loci across three growing seasons and statistical models. Gene-based association analysis identified the promoter variants Chr4:31203262 (C/T) in NAL1 and Chr7:7310528 (G/A) in ANT1 as the lead polymorphisms, with the favorable C and G alleles associated with increased tiller number, respectively. In addition, nine putative candidate loci showing suggestive associations across three growing seasons were identified as putative candidate breeding resources. These results highlight the importance of integrating multi-year phenotyping with GWAS to prioritize loci showing reproducible associations across three growing seasons and provide valuable candidate genetic resources for future molecular improvement of rice adapted to the South China rice-growing region.