Gene Flow and Genetic Structure of Wild Soybean (Glycine soja) in Japan

Abstract

In many parts of Japan cultivated soybean and wild soybean are sympatric. The objective of this study was to measure gene movement from cultivated soybean to wild soybean and within wild soybean in natural populations in Japan. Seven microsatellite markers that were found to have particularly high ability to discriminate components of the soybean complex in Japan were used to measure the extent of pollen and seed dispersal within and between populations of G. soja at seven localities (14 populations) in northern, central, and southern regions of Japan (1334 seeds/168 individuals) were measured. Each G. soja site consisted of two neighboring populations (100 m–2 km apart), which were adjacent to ( <5 m), or isolated from ( >50 m), cultivated soybean fields. Gene flow from G. max to G. soja was not detected. However, in populations of G. soja, the outcrossing rate ranged from 0–6.3% (average 2.2%), and the dispersal distance of pollen ranged from 5–25 m (average 10.5 m). In addition, 13 individuals of G. soja (7.7%) collected in four populations were assigned to neighboring populations (100–400 m). The results suggest the occurrence of long‐distance seed dispersal in G. soja Spatial autocorrelation analysis revealed a clear isolation by distance model, and a strong positive genetic correlation among individuals was observed within a range of 400 m (r = 0.168–0.551). Gene flow by hybridization among G. soja individuals occurs more frequently than the rare hybridization events between G. max and G. soja in Japan.