Genetic Diversity and RAPD-Based DNA Fingerprinting of Some Members of the Cucurbitaceae in Nigeria

The genetic variability and relatedness of 14 species from 12 genera of the Cucurbitaceae, an important horticultural family were examined using Random Amplified Polymorphic DNA (RAPD). The taxa (Luffa aegyptiaca, Luffa acutangula, Cucumis melo, Cucumis sativus, Telfairia occidentalis, Trichosanthes cucumerina, Cucurbita moschata, Lagenaria breviflora, Cucumeropsis mannii, Zehneria scabra, Melothria scabra, Momordica charantia, Citrullus lanatus and Coccinia barteri) collected randomly from the southern part of Nigeria were genotyped and their systematic interrelationships compared. DNA extracted from silica dried leaves of the species using DNeasy Plant Mini Kit (QIAGEN, Amsterdam, Netherlands) was amplified with fifteen Random Amplified Polymorphic DNA primers. The genetic similarities for the 14 species were estimated from banding profiles as a basis for dendrogram construction via the neighbour joining method conducted under parsimony criteria using DARWin 6 and NTSYS-PC. The RAPDs amplified 317 bands ranging from 120 to 2531bp producing monomorphic and polymorphic bands indicating considerable genetic differences among the studied cucurbit species. The genetic tree revealed circumscription of three major clusters. The first, a heterogeneous cluster comprising two groups with Telfairia occidentalis, Trichosanthes cucumerina and Luffa forming one group, and Cucurbita moschata, Lagenaria breviflora and Cucumeropsis mannii forming a second group. The second cluster consists of three groups; Group I comprised Zehneria scabra and Melothria scabra that clustered separately from Momordica charantia. Group II comprised closely related species Cucumis sativus and Cucumis melo. Group III comprised separately clustered Citrullus lanatus. The third cluster consisted of a group which comprised Coccinia barteri. The genetic diversity ranged between 40 to 99.9 %. The results were indicative that RAPD markers are useful in assessing genetic diversity of the Cucurbitaceae, providing an invaluable new tool for biological research and will be essential in expediting the process of breeding new and better adapted cucurbit species.