Current status of genetic regulation in soybean seed size

Seed size is one of important agronomic traits for yield and appearance quality in soybean, which is one of the major objectives of breeding with great economic values.Soybean seed size is coordinately determined by the development of embryo, endosperm and seed coat.At least 309 QTL loci are related to seed size in soybean, however, most of their molecular functionals have not yet been identified.Among the 17 seed size- associated genes, most of them are predominantly controlled by the internal genetic information from maternal and zygotic tissues, and others are phytohormones signals, including 12 positive and 4 negative regulatory genes.The PP2C-1, Gm20OX, CYP78A and others are expected to be elite gene targets for molecular design breeding of soybean, which play key roles in regulating seed size during plant ontogeny without affecting seed qualities.In this review, we summarized the identified QTL related to seed size of soybean by linkage and association analysis, with particular emphasis on the genetic and molecular mechanisms of newly identified regulators in soybean.Future research and hot spots were also discussed in order to provide theoretical reference for the molecular regulation mechanism and the innovation of high-yield breeding technology in soybean.