Genetic Structure Analyses of Ectomycorrhizal Fungus, Rhizopogon roseolus by SSR Markers in Three Spatial Scales

Abstract

We investigated the genetics structure of Rhizopogon roseolus by using microsatellite markers (SSR, Simple sequence repeat) in three geographical scales: fine-scale, local scale and national scale. Fine-scale genetic structure analyses revealed genet size of R. roseolus is small (Avg. 0.6 m, ≦1.6 m) and genet turnover is frequent (95.8％ within 1 year), indicating R. roseolus depends on frequent sexual reproduction. Spatial autocorrelation analyses detected significantly positive genetic structure in the shortest distance class (0‒4 m), within which dense spore mass is directly dispersed into soil from melted sporocarps after maturity. Local scale analyses in Tottori Prefecture revealed that R. roseolus populations in the Tottori sand dune had higher genetic diversity than those of outside, and gene flow between the outside and inside of the dune was restricted in this spatial scale (e.g. F_ST＝0.243 for 32.2 km). STRUCTURE analyses were conducted in R. roseolus strains from 21 regions in Japan and found 4 genetic clusters corresponding to the geographical origins of the strains. Our results indicate that restricted gene flow of R. roseolus causes genetic differentiation between regional populations. Unique genetic variations among differentiated populations could be useful resources for R. roseolus breeding.