Quantitative trait loci analysis for rice seed vigor during the germination stage

Seed vigor is an important characteristic of seed quality, and rice cultivars with strong seed vigor are desirable in direct-sowing rice production for optimum stand establishment. In the present study, the quantitative trait loci （QTLs） of three traits for rice seed vigor during the germination stage, including germination rate, final germination percentage, and germination index, were investigated using one recombinant inbred line （RIL） population derived from a cross between japonica Daguandao and indica IR28, and using the multiple interval mapping （MIM） approach. The results show that indica rice presented stronger seed vigor during the germination stage than japonica rice. A total of ten QTLs, and at least five novel alleles, were detected to control rice seed vigor, and the amount of variation （R2） explained by an individual QTL ranged from 7.5% to 68.5%, with three major QTLs with R2〉20%. Most of the QTLs detected here are likely to coincide with QTLs for seed weight, seed size, or seed dormancy, suggesting that the rice seed vigor might be correlated with seed weight, seed size, and seed dormancy. At least five QTLs are novel alleles with no previous reports of seed vigor genes in rice, and those major or minor QTLs could be used to significantly improve the seed vigor by marker-assisted selection （MAS） in rice.