Genetic diversity and sampling strategy of Scutellaria baicalensis germplasm resources based on ISSR

Destruction in wild resource and decline in genetic diversity of Scutellaria baicalensis are becoming a big problem urgently needed be dealt in China. To help efficiently utilize and conserve this medicinal plant resources, ISSR analysis was employed to reveal genetic diversity of 107 S. baicalensis accessions consisting of 82 wild and 25 cultivated germplasm resources from 6 populations in two main producing provinces in China. Only eighteen ISSR primers that resulted in accuracy and credibility, high polymorphism, well stability PCR products were selected. The maximal and minimal bands resulted from an ISSR primer are 35 and 18 respectively with a total of 480 bands were resolved in the agarose gels with an average of two alleles per locus. As indicated by the index of genetic diversity (Na = 1.96, Ne = 1.39, He = 0.25, I = 0.39), there were richness of genetic diversity in the collected samples and that the S. baicalensis germplasm had a large representativeness as primary collection. Cluster analysis by UPGMA and STRUCTURE placed the 107-germplasm resources into three linkage clusters. The samples from all the collection locations were clustered together, but the populations from one province were not clustered together. Compared to the RS and SW strategies, the LDSS proved to be more representative for core collection construct of S. baicalensis and the best sampling ratio was 10.3 % of the total germplasms. Finally, we found that the mini core collection by LDSS was composed of 11 accessions with high genetic diversity (Na = 1.82, Ne = 1.40, He = 0.25, I = 0.39). To verify the reliability of sampling strategy, the t test was used to evaluate the representativeness between core collections (constructed by LDSS), primary and reserve collection. Our results showed that no significant difference was found in the two important genetic parameters He and I (P > 0.05), thus suggesting that the LDSS will provide a rational sampling strategy for constructing a core collection of S. baicalensis germplasm resources in the future.