High levels of gene flow constraints population structure in Mucuna pruriens L. (DC.) of northeast India

Medicinal legume Mucuna pruriens L. (DC.) is an ecologically and economically important species known world-wide for anti-Parkinson's drug L-Dopa. The plant is native to eastern India which includes parts of northeast India where it has long history of cultivation. Recently, with the discovery of novel medicinal properties and agronomic benefits, the prospects for its large-scale cultivation in the region is growing necessitating development of improved cultivars. However, little data is available on genetic diversity and population structure from its native range to use as resource base for future molecular breeding works and conservation planning. Here we describe first empirical study on genetic diversity and gene flow of M.pruriens from northeast India based on AFLP markers. The high estimates of Jaccard's coefficient and Shannon's index reveal good genetic diversity supporting centre of origin theory. However, pair-wise estimates of genetic differentiation (FST, Nei's D) were low and AMOVA revealed no evidence for genetic structuring suggesting high levels of gene flow and absence of genetic drift or bottleneck events. Clustering based on UPGMA and STRUCTURE analyses were in conformity with these findings, but point to existence of two independent gene pools representing perhaps Assam plains and eastern Himalayas – the two disparate components of geographically diverse northeast India. The mechanisms underlying such variation besides implications on genetic diversity along with scope for future investigations are discussed.