Soybean cultivars which occupy a majority of the U.S. acreage trace to only a few maternal parents. According to a recent report (1972) by the National Academy of Sciences, the maternal ancestors and their combined frequency of occurrence in the parentage among Northern and Southern varieties are: 'Mandarin' 51 %, 'Illini' 23%, 'Tokyo' 11 %, 'Dunfield' 8%, 'Mukden' 4%, and 'Roanoke' 4%. Four of these parents are introductions from Manchuria, one from Japan, and one is of unknown origin.