Biosystematics of the Dioscorea species of western ghats using chemical and molecular tools

Abstract

The genus Dioscorea, a vital group in the evolution of monocotyledons, has a significant place in the systematic studies. The present study reports the biosystematics and phylogenetic relation among 15 Dioscorea species collected from south India; D. alata, D. belophylla, D. bulbifera, D. composita, D. esculenta, D. floribunda, D. hispida, D. kalkapershadii, D. oppositifolia, D. pentaphylla, D. pubera, D. rotundata, D. tomentosa, D. wallichii, D. wightii  based on the morphological, chemical and molecular studies. HPTLC chemical profile using standard marker compound diosgenin, groups the two exotic species D. composita and D. floribunda into one clad with D. rotundata and D. esculenta as allied species, while the true native species forms the second clad. The genetic diversity analysis of Dioscorea species were carried out using the universal DNA markers, matK and chloroplast spacer region rpl36-infA-rps8. The dendrograms obtained using ‘neighbour joining’ methods of the two sets of markers distinctly delimit the 15 species and placed them into 2 main clusters; the native species and the exotic species. The study revealed that the two exotic species, D. floribunda and D. composita were distinct in their chemical and molecular constitution compared to the Indian Dioscorea species, suggesting the correlation of phytogeography as well as evolutionary phenology to the secondary metabolite distribution and genetic constitution.