Glycine gracilis Genome sequencing

Semi-wild soybean (Glycine gracilis) is a unique type of soybean retaining both wild and domesticated characteristics and provides an intermediate type as well as an important node for Glycine population structure investigation to understand the process of soybean domestication. In this study, a semi-wild soybean (Maliaodou) and a wild soybean (Lanxi 1) collected from the lower Yangtze regions were deep sequenced while the other 9 semi-wild lines were sequenced to 4-fold genome coverage. Sequence analyses revealed that (1) ten semi-wild soybean lines mainly fell into the group with wild lines instead of grouping an independent phylogenetic branch; (2) a mixed population structure of three domestication-related Glycine species (G. max, G. soja and G. gracilis) and highly progression among them were observed; (3) over putative 100 selective loci by artificial selection were identified by selective sweep analysis, including those related to development of seed size. Our results suggested the hybridization origin for semi-wild soybean. The genetic introgression via hybridization may play an important role in soybean domestication, which made a complex Glycine population structure.