Interspecific gene flow and the origin of semi‐wild soybean revealed by capturing the natural occurrence of introgression between wild and cultivated soybean populations

With 6 figures and 4 tables Abstract The cultivated soybean is domesticated from the wild soybean. Nevertheless, the origin of a semi‐wild‐type (Glycine gracilis) intermediate in morphology between the wild and cultivated species has not been very clearly established. The current hypothesis is that it is formed by hybridization between wild and cultivated soybeans. However, this theory is based on molecular data and lacks undisputed evidence, owing to no actual insight into the morphological behaviour of the occurrence of natural introgression. Phenotypic evidence is required in addition to molecular analyses. We investigated wild and cultivated soybean populations and captured the process of natural introgression between wild and cultivated soybeans as the direct and crucial evidence for the interspecific gene flow. Normal wild and cultivated soybean seeds from natural and cultivated populations generated G. gracilis‐type plants, which revealed the speciation of G. gracilis type. Our results demonstrated that the semi‐wild soybean type originated from reciprocal hybridizations between wild and cultivated soybeans. Phenotypically different cytoplasmic impacts between the wild and cultivated cytoplasmic genomes occurred in G. gracilis.