Genetic relationships among species of the genus Diplotaxis (Brassicaceae)using inter-simple sequence repeat markers

Inter-simple sequence repeat (ISSR) amplification was evaluated for its app licability as a genetic marker system to establish relationships among ten Diplotaxis species. ISSR amplification generated multiple banding profiles with the 12 primers from all DNA samples, with an average of 41.2 fragments per primer This average was clearly higher for the 5' triple-anchored prim ers than for other primers. The banding profiles were highly repeatable acr oss separate PCR runs. DNA mixing procedures were found to be appropriate s trategies to generate banding patterns representative of each species studi ed. Similarity values were calculated considering 494 ISSR bands, and a den drogram was constructed based on the similarity matrix. The ten Diplotaxis species were clustered into two major groups. The first group consists of f ive species, Diplotaxis tenuifolia and Diplotaxis cretacea, and Diplotaxis muralis with their putative parents (D. tenuifolia and Diplotn;ris viminea) . In the second group three species are clustered that are closely related (Diplotaxis virgata, Diplotaxis catholica and Diplotaxis siettiana), in add ition to Diplotaxis harra, and Diplotaxis erucoides, which has lowest simil arity values with the rest of the species studied. The two groups defined i n the present work may be concordant with the idea suggested by several aut hors of a biphyletic origin for Diplotaxis. The genetic relationships among the ten Diplotaxis species estimated by the polymorphism of ISSR markers a re in agreement with those previously inferred by other morphological, bioc hemical and molecular data, indicating the reliability of the ISSR approach for this purpose.