Genetic Diversity of Rhododendron simsii Populations on Dabieshan at Different Life Stages Based on SSR Markers

Objective Microsatellite markers were used to compare the genetic diversity and genetic structure of Rhododendron simsii populations at four different life stages sampled from Huangshizhai of Dabieshan region to clarify the mechanism of genetic diversity among different age groups.

Method  The populations of R. simsii were divided into four age groups (old trees, adult, juvenile, and seedlings) according to their sizes of basal diameter and numbers of branches. Twelve SSR markers were used for PCR amplification, and the products were subjected to 6% polyacrylamide gel electrophoresis, which were further visualized through silver staining. The "0/1" matrix was constructed and POPGENE 32.0 software was used to analyze the genetic diversity. Based on Nei's genetic distance, UPGMA dendrogram was constructed with MEGA 5.0 software.

Result  Different genetic diversities were observed in the four R. simsii populations, the lowest genetic diversity was observed in seedlings population, followed by old trees population, while the highest genetic diversity was observed in juvenile population. The observed and effective number of alleles per locus ranged from 3 to 9 and 2.254 9-6.129 7, with the average of 5.08 and 3.460 5, respectively. Moreover, HO and HE were in the ranges of 0.676 4-0.881 2 and 0.607 7-0.690 7, respectively. The Shannon's information index (I) was the highest in juvenile population, followed by adult population, and lowest in seedling population. Fis and Fit ranged within-0.638 3-0.174 4 and-0.615 1-0.270 6, with the mean of-0.294 6 and-0.162 1, indicating the outcross took place frequently. In particular, the AMOVA analysis showed that 89.76% of genetic variation was maintained within age groups, while only 10.24% presented among age groups. Frequent gene flow was observed, as only one locus showed Nm less than 1.0.The genetic identify between adult and juvenile groups was the highest.

Conclusion High genetic diversity existed among R. simsii populations located on Huangshizhai. Moderate differentiation was observed, which was maintained between age groups.