Abstract

Swertia chirayita is a highly valued but vulnerable medicinal plant species of Nepal. Its populations are declining in natural habitats due to over exploitation. Twenty-seven inter-simple sequence repeats (ISSR) primers were used to assess the genetic diversity and population genetic structure of 42 genotypes representing six natural populations of S. chirayita, from Nepal. Of the total 479 bands amplified by 27 ISSR primers, 473 (98.18%) were polymorphic, indicating very high level of genetic diversity at species level. Percentage polymorphism value for different primers ranged from 83.3 to 100% with an average of 98.18%. Polymorphism information content (PIC) value ranged from 0.88 to 0.93 with an average of 0.91. Cluster analysis performed with NTSYS pc statistical package using Jaccard’s similarity coefficients generated from ISSR binary data matrix showed that, all 27 ISSR primers separated 42 individuals into two major clusters and six sub clusters at the similarity level of 0.24. The average value of Nei’s genetic diversity (H) and Shannon’s information index (I) equaled 0.276 and 0.423, respectively at species level. The coefficient of genetic differentiation (G_ST) amongst populations of S. chirayita was found to be high (0.548) with restricted gene flow (N_m=0.4829). Analysis of molecular variance showed that genetic diversity within populations is slightly higher (50.9%) than among populations (47.6%). The present genetic diversity assessment of S. chirayita populations has been of immense importance to understand the cause of its vulnerability and has furnished valuable insights for its conservation and sustainable utilization.

Key words: Polymerase chain reaction, inter-simple sequence repeats (ISSR), genetic diversity, polymorphism, population genetics.