Genetic relationships and variation in the tropical mimosoid legume Desmanthus assessed by random amplified polymorphic DNA

A number of Desmanthus spp. are being evaluated for forage potential on clay soils in the tropics and subtropics and three cultivars have already been released in Australia. These accessions have been chosen from the large number of Desmanthus accessions collected from the Americas over the last 40 years. The utilization of this genetic resource is dependent on understanding the diversity within and between species. Hence 284 accessions, representing 11 species, were analysed using RAPD markers. There was considerable polymorphism in D. virgatus, D. leptophyllus and D. pernambucanus but this was not always uniform across the geographical range of these species. There was little polymorphism in D. pubescens. Few accessions of D. acuminatus, D. paspalaceus and D. tatuhyensis were represented in the collection, but these species, which have an almost sympatric distribution in Paraguay/Uruguay/Argentina/Brazil, showed affinities to D. leptophyllus and to each other. D. pernambucanus was the only species with representatives from regions other than the Americas, suggesting that this species in particular has the capacity to colonize new regions. The analysis indicated that the non-American D. pernambucanus germplasm probably originated from Brazil.