Genetic Structure and Diversity of Glycyrrhiza Populations Based on Transcriptome SSR Markers

Abstract

Glycyrrhiza is a widely used traditional Chinese herb with medicinal value. Recently, however, Glycyrrhiza biodiversity has faced an unprecedented threat due to its increasing demand and sharp reduction in number and population. Therefore, we have studied Glycyrrhiza’s genetic diversity to reveal its distribution pattern and evolutionary mechanism. Towards this end, a total of 736 samples from 43 populations of four Glycyrrhiza species (G. uralensis Fisch., G. inflata Bat., G. glabra L., and G. pallidiflora Maxim.) were collected, with nine simple sequence repeat (SSR) markers developed in order to evaluate the genetic structure of populations. Results show that G. uralensis has the highest genetic diversity while G. inflata has the lowest. Moreover, the overall genetic diversity of all four species is higher than that of each individual species, revealing that Glycyrrhiza is genetically diverse. In terms of interspecies differentiation, the average observed heterozygosity is lower than the expected heterozygosity, implying a heterozygote deficiency in more homozygous populations. UPGMA and PCA indicate high genetic distance, with the furthest distance found between G. pallidiflora and G. inflata. Furthermore, AMOVA results show that genetic variation between species is more significant than genetic difference between geographical regions, indicating a high gene flow. Likewise, genetic variation within populations is significantly higher than between populations or among species, indicating a strong natural selection within populations. In sum, our study provides a scientific basis for the rational development, protection, and sustainable utilization of germplasm resources.