Genetic Diversity And Mating System Of Malania Oleifera,an Endangered Species With Extremely Small Population

Malania oleifera is an endangered tree species with high utilization value in the karst areas of southwest China.Its seeds are rich in oil and with the highest nervonic acid content that has been found.While having high ecological and economic value,M.oleifera resources are scarce.Therefore,scientific management and protection of the wild natural group resources is particularly important.However,the genetic diversity background of the M.oleifera population is still unclear.In this study,an efficient SSR molecular marker was developed based on the whole genome sequence of the M.oleifera,the typical extremely small population in the fragmented habitat was taken as the research object,carried out a survey of each tree,systematically evaluated its age structure and growth status,analyzed genetic diversity and mating system,and finally clarified the generation diversity of the extremely small population level,gamete contribution,mating pattern and other genetic characteristics,speculate on the endangered system,and provide reference for formulating effective M.oleifera germplasm resource protection and utilization strategies.The main results of this study are as follows:(1)Developed the high polymorphism SSR molecular marker.651,969 SSR sites were identified in the genome,and the SSR sequence is dominated by AT bases.Further experiment developed 15 nuclear SSR,3 chloroplast genome SSR,and 2 mitochondrial genome SSR with stable amplification and high polymorphism,which provide important research tools for subsequent genetic analysis.(2)The extremely small population of M.oleifera is seriously affected by human activities,and the age structure of the population is incomplete.The population is isolated,and the fruit is heavily eaten by animals.It is common for individuals close to adulthood to fall or die,lack of seedlings,and the number of adults is rare.(3)The genetic diversity of the population is low,and the genetic diversity of seedlings is slightly lower than that of adults.The average H_o is 0.0355,and the average I is 0.652.There is no genetic differentiation within the population,and the recent bottleneck effect has caused a large number of alleles to be lost.(4)The gamete contribution among adults is unbalanced,the gene exchange is weak,selfing exists and the degree of inbreeding is high.There is a big gap in the number of progeny of different adults.5seedlings did not match their parents in the population,and the average parental inbreeding coefficient was 0.176.Based on the above results,we believe that human activities have led to the fragmentation of the habitat and the contraction of population.The lack of adults with reproductive capacity leads to the increase of inbreeding or self-breeding rate,and the decrease of genetic diversity.The long-term inbreeding decline may eventually lead to the decrease of the adaptability which may be one of the reasons for the endangerment.Therefore,the genetic protection of M.oleifera must begin with increasing gene flow among populations.