Ribosomal DNA variation and phylogenetic relationships among Cajanus cajan(L.) Millsp and its wild relatives

Genomic DNA from eight species of Cajanus and six accessions and varieties of Cajanus cajan were digested with 10 restriction enzymes and probed with full length ribosomal gene (pTA71) from wheat and rDNA intergenic spacer re gion (IGS) flanked by 25S and 18S rDNA gene of Vicia faba. The length of th e rDNA repeat units in Cajanus flanked by EcoRV sites was between 10.9 kb a nd 11.9 kb, Three rDNA repeat unit length classes were identified among the eight species. Restriction fragment length polymerphisms (RFLPs) between t he species were readily detected in all the enzyme-probe combinations, howe ver, RFLPs could not be detected between the accessions and varieties of C. cajan, The inter-specific RFLPs were used to construct a dendrogram for an alysing the genome relationships. The dendrogram revealed a close relations hip between the cultivated species C. cajan and the wild species C. scaraba eoides, Our data did not support the view that C. cajan could have evolved from a hybridization between C. scarabaeoides and C. lineatus. The Australi an species C. scarabaeoides and C. reticulatus were closely related to the Indian species C. cajan and C. platycarpus, respectively. Therefore, the ob servation generalizing that Australian species of Cajanus are less closely related to the Indian species could not be favoured. Among the species stud ied, C. goensis and C. lineatus were distantly related to the cultivated sp ecies and other wild relatives.