Genetic Diversity Analysis Of Reaumuria Soongorica Maxim. In Alxa Desert Area

The Alxa Desert Area is a typical desert region with a large scale in China.As an extremely xerophytic salt-tolerant undershrub,Reaumuria soongorica Maxim.is one of the most widely distributed plant species in the desert.Under the long-term effects of harsh environment,Reaumuria soongorica Maxim.has evolved many forms of adaptation in terms of morphologicalstructure,physiological functions and genetic characteristics.In this study,the genetic characteristics were considered to understand the adaptation mechanism of plants to the environment under long-term harsh conditions.The genetic diversity and differentiation of 10Reaumuria soongorica Maxim.populations in different habitats in Alxa desert area were analyzed by SSR?Simple Sequence Repeat?molecular marker technology to explore the effects of climate and soil factors on their morphological and genetic characteristics.The main conclusions are as follows:1)The correlation analysis between morphological characteristics and environmental factors showed that there was a significant difference between the two morphological indices?P<0.001?,and the two morphological indices of Reaumuria soongorica Maxim.populations living in harsh habitats showed a low level.Soil organic matter was significantly correlated with the height of Reaumuria soongorica Maxim.?P<0.05?;There was a significant correlation?P<0.05?between Reaumuria soongorica Maxim.and other factors including relative humidity,effective accumulated temperature,soil available phosphorus and soil organic matter in 20 cm-30 cm soil layer.In addition,soil pH values in all plots were greater than 7 and less than 10,showing weak alkalinity.2)SSR genetic diversity analysis indicates that the genetic diversity of Reaumuria soongorica Maxim.was abundant.The percentage of polymorphic bands?PPB?was as high as 96.26%.Furthermore,at species level,the Nei's gene diversity index was 0.2185 and the Shannon's information index is 0.3451.The genetic differentiation coefficient(G_ST)was 0.7202,the genetic differentiation was at a high level and most of the genetic variation?72.02%?existed between the populations.The variations of inter-population and intra-population were extremely significant?P<0.001?.The gene flow was at a low level?Nm=0.1943<1?,which suggested that less gene exchange occurred among populations.At the population level,the trend of Nei's gene diversity index was basically consistent with Shannon's information index.The highest value of the Reaumuria soongorica Maxim.population was in YinGen?0.0820;0.1315?,while the lowest value was in LuanJingtan?0.0421;0.0794?.Thus,the Reaumuria soongorica Maxim.population in the YinGen has the most abundant genetic diversity;The genetic differentiation degree of the 10Reaumuria soongorica Maxim.populations were high,which proved that the Reaumuria soongorica Maxim.in the research area has a good adaptability to the habitat.3)Cluster analysis results showed that:the populations could be clearly distinguished from each other,the populations with high genetic similarity were clustered together,and all the Reaumuria soongorica Maxim.populations were clustered into two categories.The YinGen?No.7?population,far from other populations,was divided into one group alone,and the rest were gradually clustered into another group.Mantel test results show that there was no significant correlation between genetic distance and geographic distance.4)Analysis of correlation between genetic diversity and ecological factors:there was a significant difference correlations?P<0.05?between the annual mean temperature and the number of alleles?Na?,the relative humidity,the Nei's gene diversity index,the Shannon diversity index,the effective accumulated temperature,the polymorphic locis and percentage of polymorphic bands.The results of stepwise regression analysis showed that the annual average temperature,relative humidity,and effective accumulated temperature had a significant effect on the genetic characteristics.5)The results showed that the Reaumuria soongorica Maxim.in Alxa desert area has abundant genetic diversity,and the genetic differentiation was at a high level.Therefore,the Reaumuria soongorica Maxim.has good adaptability to different habitats,and its genetic characteristics are affected by the hydrothermal conditions of the habitats.