Assessment of genetic diversity of Saraca asoca (Roxb.) De Wilde: a commercially important, but endangered, forest tree species in Western Ghats, India

Abstract

Abstract Background Saraca asoca (Roxb.) De Wilde is a valuable tree used in traditional medicine against a variety of ailments. Almost all parts of the tree are used for various commercial herbal preparations. Due to overexploitation, the species is rapidly disappearing from Western Ghats where it is native and grew extensively until recently. Conservation of this important medicinal plant is therefore an urgent need. To plan effective conservation strategies, a scientific assessment of the genetic diversity and distribution is needed. Methods Random Amplified Polymorphic DNA fingerprinting was employed and the population genetic structure of seven wild and three cultivated populations totalling 160 individuals of S. asoca in the Western Ghats region of Karnataka, Maharashtra and Goa for analysis. Results Variation of 89% was observed within populations while 11% was observed among the populations of S. asoca. Gene flow (Nm) of 2.01 was observed, and 0.19 was the degree of genetic differentiation recorded. Unweighted Pair Group Method with Arithmetic average (UPGMA) cluster analysis generated a dendrogram that showed an admixture of all genotypes but with two major clusters, which was also supported by a STRUCTURE-based Bayesian model. One wild population was well, but inexplicably, differentiated from the rest. Conclusions The study shows that there is still considerable genetic diversity existing in natural populations of S. asoca, suggesting good natural cross-pollination, giving encouraging indications that the gene pool is under no immediate threat. Any conservation strategy should utilise the observed genetic variation in the choice of planting stock for programmes of conservation, propagation and reforestation.

Keywords

• Genetic diversity
• Conservation
• RAPD
• Forest biology