Speciation of genus glycine and origin of cultivated soybean

Cytogenetic, morphological, and seed protein studies suggest that G. soja is the wild ancestor of the cultivated soybean. Linguistic, geographical and historical evidences pinpoint the eastern half of north China as the area from which soybean emerged as a domesticate during the 11 century B.C. and then spread to other southeast Asian countries. Perhaps Manchuria should be designated as a secondary gene center and the eastern half of north China should be the primary center. Due to the fact that soybeans are day-length sensitive, they spread much easier between east and west than between north and south. The soybeans grown in Korea are derived populations from the northeast China and north China, and those grown in Japan are derived from southern Korea and central China. The number of USA soybean collections is quite small when compared with that of cereal crops which are two to five times larger. Nowadays there is considerable genetic erosion in the world. So most of genetic diversity will have disappeared soon without any systematic conservation effort.