Morpho-genetic divergence and population structure in Indian Santalum album L

KEY MESSAGE: Morpho-genetic divergence study on Santalum album suggested maximum divergence is present in the south Indian populations with propagation throughout the rest of India from the south. Santalum album L. is highly valuable among Indian forest tree species and considered as the second most expensive wood in the world. Sandalwood oil present in the heartwood of the tree is used in perfumery, aromatherapy, and pharmaceuticals. Due to its high value heartwood oil, sandalwood trees are being harvested unsustainably from natural populations, resulting in a substantial decline in populations which has led to its inclusion in the vulnerable category of the IUCN Red List. Management of this important tree species in its natural area needs critical attention, because it may face a loss of genetic diversity due to exhaustive exploitation. The present study is the first of its kind that aimed to evaluate morphological and genetic variation as well as population structure of S. album using different markers assay from geographically widespread populations of India. A total of 37 primers (15 RAPD and 22 ISSR) were used to characterize total genetic diversity in S. album. RAPD markers detected 69.94% polymorphism, while ISSR markers were able to detect 72.92% polymorphism in the species. Based on the polymorphic information content, marker index, and resolving power, RAPD markers were found to be slightly superior to the ISSR markers. The UPGMA dendrogram based on cumulative RAPD and ISSR data grouped the accessions in two main clusters, which was also supported by the principal component analysis. AMOVA analysis suggested that maximum genetic variation was present within populations (RAPD 86.59%; ISSR 85.40%), with less variation among populations (RAPD 13.41%; ISSR 14.60%). Furthermore, maximal morpho-variations were found to be present in the south Indian populations. Morphological and genetic data did not show correlation, but both the markers showed a goodness-of-fit correlation (r = 0.44: p < 0.0001). The study revealed the presence of low genetic variability in S. album, which mandates immediate attention towards its sustainable utilization, propagation, and long term conservation.