Genetic insights into diversity and population structure of ashwagandha (Withania somnifera (L.) Dunal) using EST-SSR, ISSR and SSR markers: Implications for enhancing agricultural and industrial value

Abstract

Despite rising preference for herbal remedies over synthetic products, market demand for the crucial Ayurvedic herb Ashwagandha is unmet due to limited research on its genetic diversity. This study addresses this gap by utilizing 90 primers including Simple Sequence Repeats, Expressed Sequence Tags-SSRs and Inter Simple Sequence Repeats to assess the genetic diversity and population structure of 80 diverse Ashwagandha genotypes. The study confirmed the cross-transferability of 19 SSRs underscoring their future utility in diversity analysis. A total of 133 alleles were generated with an average of 5.32 alleles per primer. UBC 826 (0.89, 13.15) and EMS-12 (0.87, 10.88) were notable for their highest polymorphic information content and resolving power, respectively. These markers, characterized by the highest marker index, facilitated the identification of unique genetic profiles essential for selecting genetically diverse and superior breeding lines effectively. EMS-12, linked to isoprenoid biosynthesis, plays a crucial role in withanolide production. Thus, this primer can be incorporated into genetic maps of ashwagandha to help identify quantitative trait loci associated with secondary metabolite production. Remarkably, no studies have yet unraveled the genetic population dynamics of this powerful herb, prompting us to undertake this study to explore its implications further. Three subpopulations were identified in the current research, with Population 2 exhibiting the highest Shannon's Information Index, underscoring its genetic richness. The results of AMOVA revealed substantial intra-population diversity, with 94 % of the total genetic variance within groups. This diversity was further confirmed by observing genotypes from population 2 clustered into two distinct groups. Henceforth, dendrogram and principal component analyses confirmed the STRUCTURE results through consistent clustering patterns. This study uncovers genetic richness in Ashwagandha populations, offering a roadmap for selecting and breeding genotypes with optimal diversity and desirable traits to enhance cultivation. The findings hold significant potential for meeting industrial and pharmaceutical needs.