Assessment of genetic diversity among different population of five Swertia species by using molecular and phytochemical markers

The genus Swertia (Gentianaceae) is one of the most potent and traded herbs in Asian countries that has been described in the Indian, British and American pharmacopoeias as tinctures and infusions, and has also been reported in Ayurveda, Unani and Siddha traditional systems of medicines. Several Swertia species are declared as critically endangered in line with its increasing demand in therapeutic industries, and as a consequence, a gap is continuously increasing between the commercial demand and supply of Swertia herb. The present study aims to assess the molecular and phytochemical diversity among 48 accessions of five Swertia species collected from Western Himalayas, India. Using 16 inter sequence simple repeats (ISSR) and 18 random amplified polymorphic DNA (RAPD) markers, total 202 and 291 polymorphic bands were documented, respectively. Percentage of polymorphism ranged from 89% to 100%, and 75% to 95%, with an average of 94.8%, and 89.8%, respectively with the ISSR and RAPD primers. Overall, high level of intra-specific genetic diversity (Gst: 0.40; h: 0.20; I: 0.30) was observed among S. paniculata accessions whereas S. chirata accessions (Gst: 0.16; h: 0.08; I: 0.18) showed least genetic diversity. Moreover, among all the Swertia accessions, maximum yield of amarogentin (0.75 ± 0.20%), and swertiamarin (6.68 ± 0.10%) was found in the S. chirata collected from Chakrata-Deoban (Uttarakhand), followed by S. paniculata accessions collected from Triund-Trek Mountains (Himachal Pradesh) that displayed 0.66 ± 0.10% amarogentin and 5.76 ± 0.03% swertiamarin contents. Densitogram based on the complete linkage, Euclidean distance and similarity level also revealed highest phytochemical diversity among S. paniculata accessions. In the present study, both molecular and phytochemical markers visibly categorize different Swertia species and thus these approaches can be used as significant tools for the assessment of genetic diversity among genotypes of Swertia. In this study, the potent S. chirata displays a low degree of genetic diversity and gene flow, and therefore there is a major risk of extinction of this significant species. The results of the present study would be useful to identify the promising genotype and to develop conservation strategies for the elite Swertia species.