Study On Dark Septate Endophytes Of Defferent Plants In The Desert Steppe Of Siziwang Banner

Dark Septate Endophytes were a group of ascomyceteous fungi that had dark septate hyphae,typical microsclerotia and widely exsited in the plant roots.DSE played a unique ecological role in the stress environment to promote the host plants to absorb carbon,nitrogen and phosphorus.Root and soil samples of five dominant plants were collected from Adege and Gegentala plots of the desert steppe of Siziwangqi banner in Inner Mongolia,including Stipa breviflora,Artemisia frigida,Allium temiissimum,Heteropappus altaicus and Convolvulus ammannii.In this study,the ecological heterogeneity of DSE were studied by describing morphological characteristics of the hyphae and microsclerotium.The DSE strains were isolated from the plant roots,and identified according to morphological and molecular biological methods.Some selected strains were cultured under different conditions.The drought-tolerance,the growth effect of plants and the culture conditions were studied.The characteristics of DSE community composition and species diversity in the desert grassland plants of Siziwang banner.It has great reference value to fully utilize DSE resources and promote ecological restoration and vegetation restoration in desert steppe.The main results as follows:1.The roots of five dominant plants were infected by DSE,and formed typical dark-colored septate hyphae and microsclerotia.The hyphae,microsclerotia and DSE infection of the roots of the different plants and different sample plots were significantly different.Correlation analysis indicated that hyphal infection was extremely significantly positive correlation with soil available N,quantity of soil bacteria,actinomycetes and total microorganisms,and was significantly positive correlation with soil fungi quantity.The intensity of DSE colonization in DSE parts of root fragments was significantly negative correlation with soil available K and organic matter.The intensity of the DSE colonization in the roots was only significantly positive correlation with soil fungi quantity.2.The soil microbial AWCD value,functional diversity and carbon source in five plants had spatial difference by the Biolog method,and soil fertility was significantly different.Correlation analysis indicated that the hyphal infection was significantly positive correlation with Soil microbial AWCD value,Shannon-wiener index and Simpson index.The hyphal infection was greatly affected by the metabolic function and structure of carbon source of soil microorganisms.3.The isolation rate and species diversity of DSE were significantly different,the isolation rates were 1.33%?8.00%.Shannon-wiener index and Simpson index of DSE were the highest in A.frigida roots,and the DSE species of A.frigida roots were the most.The 108 strains of DSE were isolated and identified in two sampling sites,including 67 strains in Adege and 41 strains in Gegentala.All strains were ultimately divided into 4 genera by using morphology and molecular biological methods,including Pleosporales sp.,Paraphoma sp.,Phoma sp.and Alternaria sp..4.The 8-zml(Phoma sp.) and 8-zm2(Paraphoma chrysanthemicola) were the dominant strains with high DSE isolation frequency from S.breviflora roots.The 8-yh1(Pleosporales sp.) was the dominant strain with high DSE isolation frequency from the roots of C.ammannii and A.tenuissimum.The 8-xxycl(Phoma sp.) was the dominant strain with high DSE isolation frequency from the roots of A.tenuissimum.Under different peg-6 000 concentration(simulated drought stress),the drought-resistant,utilization of glucose and phosphorus of four dominant strains were significantly different.The melanin content were the highest at Wpeg-6000=7%.In the growth-promoting effect of four strains DSE on Lolium perenne,the roots were infected by four dominant strains.The results showed the highest growth-promoting effect on plants aboveground part.5.The optimum culture medium and conditions of four dominant strains were identified.The optimum medium of 8-zml and 8-zm2 were cultured using PDA medium,adding 0.4% peptone and pH=6.0.8-xxycl were cultured using lactose instead of the glucose,adding 0.4% peptone and pH=6.0.8-yh1 were cultured using maltose instead of the glucose,adding 0.4% yeast powder and pH=8.0,25? and dark culture.By comparing the colony morphology,the colony morphology changed obviously after optimization.