Morphological and genetic diversity assessment of Rheum australe D. Don – A high value medicinal herb from the Himalaya, and implications for conservation strategies

Rheum australe D. Don [syn. Rheum emodi wall. ex Meissn] is an herbaceous medicinal plant used in traditional and modern systems of medicine. Due to increasing demand, the species is overexploited in their natural habitats, resulting in the loss of diversity. Therefore, conservation and sustainable utilization of this valuable species are needed. The present study assessed the morphological and genetic diversity of 120 individuals belonging to 13 distant populations of R. australe collected from west Himalaya. Significant variations (p < 0.05) were recorded in plant height, leaf width, stem diameter, and root diameter of the studied morphological parameters of the populations. A total of 120 genotypes from 13 natural populations of R. australe were investigated for genetic diversity and population structure using 20 inter-simple sequence repeats (ISSRs) primers. All primers generated 70 clear and reproducible fragments with 91.87 % polymorphism. Maximum genetic diversity (He = 0.462; Pp = 100 %) was found in the Maiktoli population, whereas it was minimum (He = 0.294; Pp = 78.57 %) in the Kuari Pass population. Analysis of molecular variance (AMOVA) exhibited high intrapopulation genetic variations (90 %) as compared to interpopulation (10 %) variations. The habitat-wise comparative assessment showed higher genetic diversity (He = 0.39; Pp = 93.81 %) in open, rocky, and grassy slope habitats. The population STRUCTURE analysis displayed that the best possible value of K was 3 for R. australe populations, as assessed by the ∆K statistics. The findings of the present study can be useful for developing conservation protocols, evolutionary genetics, genetic improvement, and management of this important medicinal species in the region.