Molecular marker-based characterization in candidate plus trees of Pongamia pinnata, a potential biodiesel legume

BACKGROUND AND AIMS Pongamia pinnata, a legume tree, has many traditional uses and is a potential biodiesel plant. Despite its importance and the availability of appropriate molecular genetic tools, the full potential of Pongamia is yet to be realized. The objective of this study was to assess genetic diversity among 10 systematically characterized candidate plus trees (CPTs) of P. pinnata from North Guwahati. METHODOLOGY The application and informativeness of polymerase chain reaction-based molecular markers [random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP)] to assess the genetic variability and relatedness among 10 CPTs of P. pinnata were investigated. PRINCIPAL RESULTS Polymorphism rates of 10.48, 10.08 and 100 % were achieved using 18 RAPD, 12 ISSR and 4 AFLP primer combinations, respectively. Polymorphic information content (PIC) varied in the range 0.33-0.49, 0.18-0.49 and 0.26-0.34 for RAPD, ISSR and AFLP markers, respectively, whereas the corresponding average marker index (MI) values for the above markers were 7.48, 6.69 and 30.75. Based on Nei's gene diversity and Shannon's information index, inter-population diversity (h(sp)) was highest when compared with intra-population diversity (h(pop)) and the gene flow (N(m)) ranged from a moderate value of 0.607 to a high value of 6.287 for the three DNA markers. Clustering of individuals was not similar when RAPD- and ISSR-derived dendrogram analyses were compared with that of AFLP. The Mantel test cophenetic correlation coefficient was higher for AFLP (r = 0.98) than for ISSR (r = 0.73) and RAPD (r = 0.84). Molecular markers discriminated the individuals efficiently and generated a high similarity in dendrogram topologies derived using unweighted pair-group arithmetic average, although some differences were observed. The three-dimensional scaling by principal coordinate analysis supported the result of clustering. CONCLUSIONS Comparing the results obtained with the three DNA markers, AFLP indicated higher efficiency for estimating the levels of genetic diversity and proved to be reliable for fingerprinting, mapping and diversity studies in Pongamia in view of their suitability for energy production purposes.