Efficiency of ISSR and RAPD markers in genetic divergence analysis and conservation management of Justicia adhatoda L., a medicinal plant

Genetic variation within and among population is the basis for survival of the population both in short and long term. Thus, studying the plant genetic diversity is essential for any conservation program. Indigenous medicinal plants like Justicia adhatoda L. which are facing high rate of depletion from the wild population need immediate attention. DNA-based dominant molecular marker techniques, random amplification of polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) were used to unravel the genetic variability and relationships across thirty-two wild accessions of J. adhatoda L., a valuable medicinal shrub widespread throughout the tropical regions of Southeast Asia. Amplification of genomic DNA using 38 primers (18 RAPD and 20 ISSR) yielded 434 products, of which 404 products were polymorphic revealing 93.11 % polymorphism. The average polymorphic information content value obtained with RAPD and ISSR markers was 0.25 and 0.24, respectively. Marker index (RAPD = 3.94; ISSR = 3.53) and resolving power (RAPD = 4.24; ISSR = 3.94) indicate that the RAPD markers were relatively more efficient than the ISSR assay revealing the genetic diversity of J. adhatoda. The Shannon diversity index obtained with RAPD and ISSR markers was 0.40 and 0.38, respectively. The similarity coefficient ranged from 0.26 to 0.89, 0.33 to 0.93 and 0.31 to 0.90 with RAPD, ISSR and combined UPGMA dendrogram, respectively. PCA derived on the basis of pooled data of both the markers illustrated that the first three principal coordinate components accounted 79.27 % of the genetic similarity variance. The mantel test between two Jaccard's similarity matrices gave r = 0.901, showing the fit correlation between ISSR- and RAPD-based similarities. Based on the results, ex-situ methods may be the most suitable and efficient measure for long-term conservation.