Classification of Soybean Cultivars Based on Mitochondrial DNA Restriction Fragment Length Polymorphisms

Abstract

Mitochondrial DNA restriction fragment length polymorphisms (RFLPs) are convenient markers for identifying cytoplasmic variation among plant cultivars. We have undertaken a systematic study to classify soybean [Glycine max (L.) Merr.] germplasm into cytoplasmic groups based on RFLPs for several mitochondrial genes. This analysis substantially increases the total number of cultivars that have been examined for cytoplasmic diversity and includes many of the maternal ancestors of currently grown cultivars. It also allows comparison with studies involving chloroplast diversity in soybean. The classification presented here is based on analyses by Southern hybridization using a cloned 2.3‐kilobase (kb) HindIII DNA probe earlier shown to differentiate those cultivars derived from ‘Lincoln’ as a maternal ancestor. We have extended these studies to include 138 cultivars and old domestic varieties and have revealed a total of four cytoplasmic groups. Probes from several other soybean genes, including genes for cytochrome oxidase and adenosine triphosphate (ATP) synthase subunits, as well as the small ribosomal RNA gene, have been used as markers to show that the diversity extends to other regions of the mitochondrial genome as well.