Phylogenetic relationships among three species of the mangrove genus Avicennia found in Indian Sundarban, as revealed by RAPD analysis

Random amplified polymorphic DNA (RAPD) markers were successfully used to identify and differentiate all the three species of Avicennia found in Indian Sundarban, to assess the pattern of interspecific genetic diversity among them and to reveal their molecular phylogeny. Ten primers amplified a total number of 221 bands under 100 loci across three genotypes with an average of 10 loci / primer. Of the total 100 loci scored, 50 were polymorphic. Thus the average percentage of polymorphism was 50. Different primers yielded a total of 7 unique bands for A. alba, 14 for A. marina and 8 for A. officinalis. The distinct RAPD bands could be cloned and used as markers for species identification. The dendrogram reveals that A. alba and A. officinalis have closer relationship between them and share a common node in the dendrogram at a 73.3% level of similarity. In comparison to other species, A. marina showed most genetic variability, suggesting utilization of this species over others in breeding programmes. Genetic distance was less between A. marina and A. alba than between A. marina and A. officinalis. Phylogenetic tree shows that A. marina is more closely related to A. alba than to A. officinalis. Extent of polymorphism and uniqueness reveals lowest genetic diversity in A. alba and therefore, demands priority of this species in conservation programme to prevent extinction.

Author(s): Surya Shekhar Das, Swati Das (Sur) and Parthadeb Ghosh*

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