Exploring wild genetic resources of Musa acuminata Colla distributed in the humid forests of southern Western Ghats of peninsular India using ISSR markers

Abstract

Musa acuminata ssp. burmannica, one of the wild progenitors contributing 'A genome' to the present-day dessert bananas, has a long evolutionary history intervened by human activities. In this study, ISSR markers were used to analyze the pattern of genetic variation and differentiation in 32 individuals along with two reference samples (viz., Musa acuminata ssp. burmannicoides, var. Calcutta 4 and Musa balbisiana) of wild Musa, which corresponded to three populations across the biodiversity-rich hot spot of southern Western Ghats of India. High levels of genetic diversity were revealed both at the species and population levels, using Nei's diversity indices. The hierarchical analysis of molecular variance showed pronounced genetic differentiation, as 96% of the total variance was fixed within population and only 4% among populations. Nei's genetic differentiation coefficient (GST=0.1823) and low gene flow (Nm=1.18) further confirmed this. The positive correlation (Mantel test) between geographic distance and genetic distance (r=0.338 P<0.001) indicates geographic isolation as one of the key factors in shaping the population genetic structure. Grouping of individuals was largely in conformity with their spatial distribution, which was confirmed by UPGMA cluster analysis and PCA scatter plot clustering all 32 individuals into three major groups along a geographical gradient. The discontinuous distribution and dwindling population due to habitat fragmentation are serious threats to prevailing genetic diversity in this species. Conservation measures based on diversity pattern are suggested for long-term preservation and sustainable utilization of this precious genetic resource. A diverse germplasm of Musa acuminata ssp. burmannica exists in southern Western Ghats as a possible repository of useful resistant traits, which can be effectively utilized for crop improvement.