Abstract: Malus sieversii is one of the national second-class protective plants and an important wild fruit germplasm resources.In this study, the M.sieversii population in Xinyuan County, Xinjiang was selected to research the genetic difference between the death and alive individuals of M.sieversii suffering from the serious diseases and insect pests than other populations, the effect of death individuals on the genetic diversity of M.sieversii was evaluated, and the genotypes of death and alive individuals were marked using the microsatellite markers.The results are as follows: ① There was no significant genetic divergence between the death and alive individuals, which indicated that the death of M.sieversii was random and out of genetic correlation;② Genetic structure of M.sieversii population in Xinyuan was not significantly influenced by tree death.The level of genetic diversity decreased slightly after the tree death, but a lot of low frequency alleles were lost;③ During the future monitoring and evaluation of the change of M.sieversii genetic resources, the number of alleles (N_a) was more suitable for effectively reflecting the variation of genetic resources than the indexes of genetic diversity.

Key words: Malus sieversii, germplasm resources, tree death, genetic diversity, SSR, diseases and insect pests, Xinyuan County, Xinjiang