The Resource Survey, Genetic Diversity And The Conservation Strategies Of Cycas Szechuanensis

Cycas szechuanensis W.C. Zheng&L.K. Fu, a new species published in1975according to a herbarium which was collected from a cultivated plant in Fuhu temple,Mt. Emei, Sichuan. It is one of the cycads that cultivated widely and has a longcultivation history in China. This species is listed by the IUCN Red List of ThreatenedPlants as category CE(Critically endangered), and it is included in the CITESAppendix II, and regarded as a category I protected species in China.In order to protect the precious living fossil plant effectively,investigations were carried out in Sichuan,Fujian, Guangdong and Guangxiprovinces to explore the exact resource and growing status.60samples wereselected for the SSR experiment to test the genetic variation, and made acomparison with other cycas. The main results are as follows:About the investigation: It is covered12locations, and we found176individuals (Add with other places, there are about350C. szechuanensisindividuals in total in China). They are in a good growing condition, and manyof them have female cones, but none of the ovules develope to seeds.About the molecular experiment: The SSR loci are from the plastid and nucleargenomes.Two of the three cpSSR loci have the polymorphic bands, the percentage of polymorphic Loci is66.67%. They can be divided into6chloroplast haplotypes, theDiversity (Ho) is0.231, the Unbiased Diversity (He) is0.247, and the Shannon indexis0.111. For the mtSSR, only one of the three loci exist three polymorphic bands,which form3mitochondria haplotypes. The Ex-situ Conservation Center of cycas atthe Fairylake Botanical Garden has the highest chloroplast haplotype diversity. Andthe individuals in Mt. Emei and Chengdu are the important resources in Sichuan. TheShaxian and Yongtai individuals should be the precious resource in Fujian province.In nuclear genome,11primers were selected from65published SSR primers incycas to do the SSR genotyping. But only the A8primer has5polymorphic bands.The Expected Heterozygosity (He) is0.605, the Shannon’s Information Index(I) is0.496, and the Fixation Index(F) is-0.695.The11primers showed the meanHe=0.337, I=0.496, F=-0.799.While for the C. fairylakea, which is rather closed toC. szechuanensis, eight of the eleven primers have the polymorphic Loci. The meanHe=0.634, I=1.242, F=-0.472. Ten of the eleven SSR primers show nodifference among individuals is because the genetic diversity of C. szechuanensisis really low.After the analysis of Structure software, all the individuals of C.szechuanensis are from the same origin. There is no mixture within the species.From the SSR analysis, all the C. szechuanensis individuals may come from thesame colon. Little variation is accumulated during the long cultivated history.So, according to the above studies, it is better to promote threatened status of thespecies as category EW(extinct wild). And effective conservation strategies should betaken. Not only do the best to protect the existing individuals but also the Ex-situConservation of cycas should make a sustainable and scientific project to do thehybridization and the back-cross.