. 2009. DNA methylation polymorphism in annual wild soybean (Glycine soja Sieb. et Zucc.) and cultivated soybean (G. max L. Merr.). Can. J. Plant Sci. 89: 851Á863. To study DNA methylation polymorphism in soybean, 20 and 27 lines of annual wild and cultivated soybeans, respectively, were selected from previously established "Soybean Core Collections in China", and subjected to methylation-sensitive amplified polymorphism (MSAP) analysis. Twenty-seven primer pairs generated 984 CG/CNG methylation sites across the 47 lines, and the data were dissected into methylation-sensitive (MS) and methylation-insensitive(MIS) polymorphisms. The calculated MSP vs. MISP for wild soybeans were 34.65 vs. 34.76%, while corresponding results for the cultivated soybeans were 47.05 vs. 47.15%, indicating higher levels of MSP and MISP in cultivated than in wild soybeans. These results were incongruent with the amplified fragment length polymorphism (AFLP) analysis of the same soybean lines, and suggested enhanced DNA methylation polymorphism due to human selection. All three markers, MSP, MISP and AFLP, enabled clustering of the soybean lines into two distinct groups each predominantly containing wild or cultivated ones. Homology search indicated that 12 out of 24 sequenced MSPs had significant similarities to known-function or predicated genes, suggesting possible functional relevance of the methylation polymorphism. No significant association between MSP and MISP or MSP and AFLP was detected. Our results suggest that DNA methylation polymorphism in soybean has been under both natural and human selections, implicating possible roles of this epigenetic modification in genome evolution and domestication.

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The extent and pattern of genetic differentiation between two naturally occurring phenotypes, grey–green leaf (GGL) and yellow–green leaf (YGL), of Leymus chinensis (Trin.) Tzvel., which colonize distinct habitats in the Songnen Prairie in northeast China, were investigated by amplified fragment length polymorphism (AFLP) analysis. Twelve selected AFLP primer pairs amplified 593 reproducible bands, of which 148 (24.96%) were polymorphic among 69 individuals taken from three populations: two natural ones (YGL and GGL1) and one transplanted (GGL2). Cluster analysis based on the AFLP data categorized the plants into distinct groups that are in line with their phenotypes and population origins, thus denoting clear genetic differentiation between the two phenotypes. This, together with their adaptation to contrasting natural habitats, suggests that the two phenotypes probably represent stabilized ecotypes. The grouping was supported by multiple statistical analyses including Mantel’s test, principal coordinate analysis (PCOORDA), and analysis of molecular variance (AMOVA). The GGL phenotype harbors a higher level of within-population genetic diversity than YGL, possibly reflecting selection by habitat heterogeneity. Although GGL2 is largely similar to its original population (GGL1), further diversification since transplantation was evident. Sequence analysis of a subset of phenotype-specific or phenotype-enriched AFLP bands implicated diverse biological functions being involved in ecological adaptation and formation of the two phenotypes.