GENETIC DIVERSITY AND GENETIC STRUCTURE OF THE RARE AND ENDANGERED RELICT PLANT CYCAS SHIWANDASHANICA

. Understanding the genetic diversity and structure of the rare and endangered relict plant Cycas shiwandashanica is the basis and prerequisite for formulating effective conservation and management strategies. In this study, the genetic diversity and genetic structure of 103 individuals from five populations of C. shiwandashanica were analyzed based on 6 pairs of SSR primers with good polymorphism and stable amplification. The results showed that at the population level, the Shannon information diversity index (I) was 0.709. The mean value of Ho was 0.453. The results indicated that C. shiwandashanica had high genetic diversity. There were significant differences among all populations. The total mean value of Wright fixed index F of the polymorphic loci of each population was -0.147, indicating that there was an excess of heterozygotes in each population. The analysis of molecular variance showed that 21% of the genetic variation existed in the population level and 79% in the individual level. The individual variation was the main source of the total variation of C. shiwandashanica . The results indicated that C. shiwandashanica had abundant genetic variation and high evolutionary potential. The maximum genetic distance between the five populations was 0.268423 (SY1/ZWS1) and the minimum was 0.049418 (SY1/MZT1). MZT1 and SY1 get together, then PFA1, and finally WWL1; This is consistent with the distribution location and distance of the wild population of C. shiwandashanica . Considering the current situation of the wild population of this species, it is suggested to establish a protection plot, carry out in situ protection, and strengthen the ex-situ protection measures such as introduction and artificial breeding. This study can provide theoretical support for the conservation of plant resources of C. shiwandashanica and has important theoretical and practical significance.