Phylogenetic relationships of the mitochondrial genomes in the genus Glycine subgenus Soja

Abstract

Restriction fragment length polymorphisms (RFLPs) of mitochondrial DNA (mtDNA) of wild and cultivated soybeans were analyzed to study their phylogenetic relationships. The observed number of differences in hybridization profiles greatly varied (1 - 17 patterns) with both the mtDNA probes and the restriction enzymes that were used. A cladistic analysis was conducted based on the RFLP data. In the parsimonious tree, four distinct groups appeared among 20 accessions of the subgenus Soja representing 20 mitochondrial genome types. Common features with regard to geographic distributions in natural populations in East Asia were observed among the mitochondrial genome types of wild soybean that belonged to the same group: one clade consisted of genome types IIg and VIIg that are detected with very low frequencies; another clade consisted of genome types Ic, Id, Ie, and Ik whose distributions are highly biased mainly in Japan. The genome types that are widely distributed in East Asia such as IVa, IVb, and Va were not grouped into the same clade. The mitochondrial genome types IIIb, IVb, and IVc, in which two different chloroplast genome types exist, belonged to the same clade. Possible changes in mitochondrial genomes during the expansion of the distribution of wild soybeans in East Asia were discussed.