Natural Variation in Contributes to Grain Size and Chalkiness in Rice.

Rice ( L.) is an important staple food crop for more than half of the world's population. Enhancing the grain quality and yield of rice to meet growing demand remains a major challenge. Here, we show that encode a MAP kinase kinase that controls grain size and chalkiness by affecting cell proliferation in spikelet hulls. We showed that , , and have a substantial effect on the -regulated grain size pathway. has experienced strong directional selection in and . Wild rice accessions contained four haplotypes, suggesting that the haplotypes present in cultivated rice likely originated from different wild rice accessions during rice domestication. -Hap1, , and were polymerized to enhance the grain length. Polymerization of beneficial alleles, such as -Hap1, , , , , , and , also improved the quality of hybrid rice. Overall, the results indicated that beneficial alleles could be used for genomic-assisted breeding for rice cultivar improvement and be polymerized with other beneficial alleles.