Genetic Diversity Estimates of <i>Santalum album</i> L. through Microsatellite Markers: Implications on Conservation

Abstract

Sandalwood ( Santalum album L.) is the second most expensive wood in the world. There are approximately 16 species of sandalwood ( S. album , S. spicatum , S. austrocaledonicum , S. yasi , S. lanceolatum , S. ellipticum , S. macgregorii , S. insulare ) occurring naturally throughout Australia, India, Indonesia, Papua New Guinea and the islands of the South Pacific. In India , S. album is found all over the country, with over 90% of the area in Karnataka, Tamil Nadu, Kerala, Andhra Pradesh and Telangana state. It is highly economic tropical tree species because of its scented heartwood and heartwood oil. Several causes have been attributed to the depletion of sandalwood population mainly amongst which theft is causing negative effect on the quality of species by constant removal of superior clones. The aim of this study was to determine the genetic diversity of S . album . For this, 177 genotypes of S. album from 14 populations of three states (Karnataka, Telangana state and Kerala) in southern India were selected. The genetic diversity and genetic structure were characterized through 25 SSR markers developed by cross amplification of different species of Sandalwood. Under this study , following genetic diver sity parameters were estimated at individual level and population level; Number of alleles (Na) 9.107, Effective number of alleles (Ne) 7.56, Observed heterozygosity (Ho) 0.187, Expected heterozygosity (He) 0.861, Shannon information index (I) 2.03, F statistics 0.89, Polymorphic information content (PIC) 0.87 and Gene flow (Nm) 4.98. The estimates of gene flow among the populations of Kodada Telangana (Nm = 15.109); IWST Karnataka (Nm = 13.62) than across other geographical populations (Nm = 9.40). Analysis of molecular variance (AMOVA) revealed that 3% of the total variation was due to differences among populations and 97% due to differences within the populations. The genetic differentiation among populations (F ST ) 0.012 at p < 0.001 was significant. Structure clustering at Ks = 3 highlighted three distinct groups with the inferred clusters i. 0.369, ii. 0.304, iii. 0.327. Structure analysis revealed that genetic structure of Kerala and Karnataka and Telangana populations were admixtures and classified in three groups. In addition, all the accessions were clearly divided into three major clusters by UPGMA dendrogram which could be further divided into five sub groups. Principal component analysis (PCA) results showed the combined variation 82.2% of these markers. This study highlights the knowledge of genetic variation in sandalwood across the herd population of sandalwood in India. The highest range of polymorphism was detected with SSR markers developed from Osyris lanceolata compared to Santalum. austrocaledonicum , Santalum. insulare and Santalum. spicatum. This study would help in conservation of the Sandal wood populations with high profile of genetic diversity and selection of clones for genetic improvement program.