Abstract: 【Objective】Grape berry size is one of important factors affecting grape appearance and the final productivity. It is a complex quantitative trait regulated by multiple genes. Mining the key genetic regulatory loci and the underlying genes for berry size related traits will help to improve grape yield. 【Method】In this study, 150 diverse grapevine varieties were selected as materials. The berry weight, seed number per berry, and seed weight were measured in 2019 and 2020, respectively. Based on high-density genotype data obtained by resequencing, the genome-wide association studies (GWAS) were carried out to detect significantly associated SNPs and predict important candidate genes.【Result】The three measured traits exhibited extensive phenotypic variation with 39.55%-68.89% of phenotypic variation coefficients; The phenotypic distribution of the observed three traits in the population showed continuous quantitative genetic characteristics; A significant positive correlation between each trait were observed in two years; Based on the phenotypic data collected in two years, a total of 150 significant SNPs were detected for berry weight. In 2019, 99 SNPs were detected, each of which contributed the phenotypic variation from 14.48% to 25.59%; In 2020, 73 SNPs were detected, explaining 16.08%-26.83% of phenotypic variation; Among these SNPs, 24 were detected repeatedly in both two years, mainly located on chromosome 1, 5, 11 and 16. Compared with the trait of berry weight, less SNPs significantly associated with the seed number were detected. A significant SNP was detected in 2019, and the phenotypic explanation value was 24.29%; In 2020, 17 significant SNPs were detected, which all located on chromosome 18; 1 and 2 SNPs located on chromosome 18 significantly associated with seed weight were detected respectively in 2019 and 2020, accounting for 23.59%-48.29% of phenotypic variation. Within the genomic region of SNPs detected repeatedly for two years, 11 candidate genes that may be related to berry weight were screened out based on the functional annotation, including ethylene signal pathway genes (VIT_05s0049g00490, VIT_05s0049g00500, VIT_05s0049g00510 and VIT_16s0100g00400), gibberellin signal pathway genes (VIT_11s0016g04630 and VIT_16s0022g02310), auxin responsive protein gene (VIT_11s0016g05640) and some important transcription factor genes (VIT_05s0049g00460, VIT_11s0016g05660 and VIT_16s0022g02330). A candidate gene VIT_18s0041g01880 (encoding a MADS box protein VviAGL11) associated with seed content was identified on chromosome 18, and different SNP genotype on this gene significantly affected the grape berry seed number and weight. 【Conclusion】A total of 150 SNPs significantly associated with berry weight were detected in two years, mainly located on chromosomes 1, 5, 11 and 16; A total of 19 significant SNPs associated with seed content were detected, mainly located on chromosome 18. Based on the results of gene annotation and genotype analysis, 11 candidate genes that may be involved in the regulation of grape berry weight including VIT_11s0016g04630 and VIT_16s0022g02310 were selected; the candidate gene VIT_18s0041g01880 was determined significantly correlated with seed content.

Key words: grape, berry size; genome-wide association studies; candidate gene