Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2004
Publication Date: 1/15/2005
Citation: Chen, Y., Nelson, R.L. 2005. Genetic variation and relationships among cultivated, wild, and semi-wild soybean. Crop Science. 14:103-144. Interpretive Summary: The closest relative of the soybean is the wild species that is the progenitor of the soybean. There are plants that are intermediate in appearance between the wild and domesticated soybean. Some people recognize this type of plants as a distinct species but in the U.S. and Europe they have been included in the same species as soybean since the 1960's. In the USDA Soybean Germplasm Collection, these types are identified as semi-wild. Our objective in this research was to use both morphological and DNA data to quantify the variation within soybean, semiwild soybean and wild soybean and to examine the relationships among these three types. Grouping plant types based on variation in the DNA was very consistent with how we had previously classified these plants based on appearance. Based on the DNA data, wild soybean has the greatest genetic diversity and semi-wild types have the least diversity. Soybean and semiwild types are more closely related to each other than to wild soybean. This information will be useful for curators of soybean germplasm collections and for breeders and geneticists who use soybean germplasm for breeding or research.
Technical Abstract: Some annual Glycine accessions are intermediate between the standard phenotypes of Glycine max [L.] Merr. and Glycine soja Sieb. & Zucc.and have been labeled semi-wild. Few studies have examined both the genetic and phenotypic relationships among G. soja, G. max, and semi-wild types by combining morphological traits and DNA markers. The objectives of this research were to quantify genetic variation within G. soja, G. max, and semi-wild accessions; to investigate the relationships among the G. soja, G. max, and semi-wild accessions; and to examine the relationships among phenotypes based on morphological traits and genotypes based on DNA markers. Ninety-two semi-wild, G. soja, and G. max accessions from the USDA Soybean Germplasm Collection were evaluated for 20 phenotypic traits and with 137 RAPD markers. Mahalanobis distances and a Jaccard genetic similarity matrix were calculated for phenotypic traits and DNA data, respectively. Nonhierarchical and hierarchical clustering as well as multidimensional scaling (MDS) were used to evaluate relationships among semi-wild, G. soja, and G. max accessions. Principal component analysis was applied to identify the morphological traits that were most significant in separating the three groups. For the accessions examined, unique RAPD markers were found for each taxonomic type. Three clusters defined by either phenotypic or DNA data are highly consistent and strongly corresponded to G. soja, G. max, and semi-wild classifications. Based on the analysis of RAPD data, G. soja accessions have the greatest genetic diversity and semi-wild accessions the least. G. max and semi-wild accessions are more closely related to each other than to G. soja accessions. This data will be useful in helping to define a core collection of annual Glycine.