Geographic differentiation and phylogeographic relationships among world soybean populations

Abstract

A fast-growing protein and oil crop, soybean was domesticated in ancient China and disseminated early in Asia and afterwards to other continents, in particular the Americas in recent centuries. After adaptation, locally developed landraces and cultivars formed a diversity of geographic-populations. In an investigation of their phylogeographic features, marker-derived traits were combined with geography-related photo- and temperature-sensitive traits to study 13 geographic-populations comprising 371 accessions. Extreme differentiation among geographic-populations was observed for flowering date (33–94 days), maturity date (79–181 days), and main stem node number (6–25 nodes). Restriction-site associated DNA sequencing revealed strong genetic differentiation among these geographic-populations, including genetic richness (alleles, 35,242–44,986) and specific-present alleles (SPAs, 0–67). More SPAs (28–67) emerged in some secondary and tertiary centers than in centers of origin (8–11). Phenotypic and genotypic clustering divided 11 of the 13 geographic-populations into the same five sets of sensitivity-similar geographic-populations and grouped the populations of northeast China and northern North America rather than center-of-origin populations as secondary centers, indicating the importance of geography-related traits in determining genetic differences among geographic-populations. A model of four soybean dissemination paths is presented: from the center of origin to the north, east, and south in Asia and from northeast China to Europe and the Americas. These findings provide a detailed phylogeographic understanding of worldwide soybeans.