Study on genetic diversity and differentiation of Panax zingiberensis C. Y. Wu et K. W. Feng

Panax zingiberensis C. Y. Wu et K. W. Feng is a perennial herbaceous plant belonging to the genus Panax (Araliaceae). It is an endangered species mainly distributed in southeastern and southern Yunnan, China. Like other species of Panax, P. zingiberensis (otherwise known as "Yesanqi") has high medicinal value and is used as a substitute of P. notoginseng by local people. In this study, the genetic diversity and genetic differentiation of P. zingiberensis was analyzed using data obtained from five DNA fragments and 12 microsatellite (SSR) markers. Results showed that the total nucleotide diversity of P. zingiberensis was just 0.00068 at the species level based on the combined analyses of four chloroplast fragments (psbA-trnH, psbM-trnD, rps16, and trnL-trnF), whereas the nucleotide diversity of nuclear ITS (P_i=0.01011) was high. In the 12 polymorphic microsatellite loci, a total of 89 alleles were identified, and the average number of alleles per locus was 7.417. Compared to other Panax species, P. zingiberensis had a relatively high level of nucleotide diversity and number of alleles. At the population level, population JG had the highest nucleotide diversity and number of alleles, whereas population JC had the lowest. AMOVA indicated that genetic variation among populations (55.03%) in the cpDNA fragment was greater than that within populations (44.97%). However, for the ITS fragment and SSR locus, genetic variation among populations (30.23% and 35.90%, respectively) was much lower than that within populations (69.77% and 64.10%, respectively). This indicated that P. zingiberensis had a certain degree of genetic differentiation at the species level, but it was not significant (P=0.01 or 0.05). At the population level, based on genetic differentiation indices (F_st', G_st'(Nei), and Rho) inferred from SSR data, population JC exhibited high differentiation from the other four populations, whereas no differentiation was observed among these populations. Structure analysis showed that JC and other populations were clustered into different genetic groups, respectively. Combined with phenotypic characteristics of the samples, structure analysis also showed that those individuals with similar morphological characteristics were not clustered together, whereas individuals of the same population had more similar genetic components. This study should help in the conservation of wild resources of P. zingiberensis.