Geographical Patterns of Variation in the USDA Soybean Germplasm Collection: I. Morphological Traits

In order to use, maintain, and increase germplasm collections efficiently and effectively, it is important to characterize the diversity of the collection. Our objective was to describe phenotypic diversity of a large sample (2250 accessions from 78 countries) of the USDA soybean [Glycine max (L.) Merr.] germplasm collection. Accessions were characterized for 17 morphological traits to determine variation within and among geographical regions. Phenotypic variation was found within all regions for most characters. The Shannon‐Weaver diversity index was relatively even across regions, bet varied widely among characters scored. Canonical discriminant analysis and clustering of the canonical means delineated four regional clusters: (i) India and Africa; (ii) China, Europe, New World, and Southeast Asia; (iii) Korea and Japan; and (iv) Southwest Central Asia. clusters containing the Korean and Chinese accessions were the most diverse. Based on the diversity and number of accessions, Africa, India, and Southeast Asia seem underrepresented in the collection.