Phenotypic diversity and genome-wide association mapping of earliness-related traits in cultivated tomato (Solanum lycopersicum L.)

摘要

Earliness is an economically important trait in tomato cultivars. Genetic mapping for earliness-related traits has been studied using segregating populations derived from interspecifc crosses. An association mapping study of the early ripening trait in tomato has yet to be published. Here, we studied a group of 191 tomato cultivars and measured the number of days to flowering (DTF), days to fruit ripening (DTR), days from flowering to ripening (DFR), and fruit weight (FW). Correlation analysis showed that FW was significantly and positively correlated with DTF, DTR, and DFR. Phenotypic comparisons between indeterminate and determinate tomato groups showed significant differences in all traits examined except for DFR. We used 273 molecular markers, including 120 SNPs, 128 InDels, and 25 SSRs, to genotype all 191 tomato accessions. Population structure and linkage disequilibrium (LD) were analyzed. We found that the accessions were structured into three main subpopulations corresponding to cherry, traditional, and contemporary accessions. LD analysis showed that LD decays over 6.9-15.4 cM in cultivated tomato, and InDel markers detected a higher level of LD than did SNPs. Genome-wide association mapping detected 23 associations for earliness-related traits; the number of associations per trait varied from four to seven, and more than half of the associations were co-localized with previously-identified QTLs or known genes. The results of our study confirm some previous QTLs and identified several potentially new loci that affect earliness in tomato.