Species Diversity,Promotion Of Growth And Drought Resistance Of Dark Septate Endophytes In Arternisia Ordosica

Artemisia ordosica Krasch,is an excellent sand fixing and semi shrub,adapted to arid and semi-arid conditions of northwest China,which plays an important role in the restoration and reconstruction of desert ecosystem.Dark septate endophyte(DSE)is a kind of endophyte that colonizes the root of host plant without causing any disease.It has similar ecological function as mycorrhizal fungi,that plays an important role in promoting plant growth and enhancing the stress resistance of host plant.In this study,soil samples and root samples in the 0-30 cm soil layers were collected from the rhizosphere of A.ordosica along the sampling sites of northwest China in 2018 and 2019.The aims of this study were to observe the temporal and spatial distribution colonization status of DSE,and its correlation with soil factors;to isolate fungi from the roots of A.ordosica and assess the species diversity of DSE fungi;the isolated DSE fungi were studied for drought stress,and the superior DSE resources were selected for inoculation experimen.In order to make full use of DSE fungi resources and provide theoretical basis for promoting desert vegetation restorations.The main results were as follows:1.The root of A.ordosica can be highly infected by DSE,forming a typical dark septate mycelium and microsclerotia structure.The average total DSE colonization rate of A.ordosica was increasing in different years,51.67%(2018)and 54.58%(2019)respectively.The colonization rates of Shapotou and Alxa were higher than that of Minqin and Dengkou.Except for Dengkou in 2019,there was no significant difference in DSE colonization between 0-10 cm and 20-30 cm from the plant.2.Spearman correlation analysis showed that the hyphae colonization rate was negatively correlated with soil alkaline phosphatase.The microsclerotia colonization rate was negatively correlated with soil organic carbon,alkaline phosphatase and available phosphorus.The total colonization rate was negatively correlated with soil organic carbon and alkaline phosphatase.The intensity of colonization was negatively correlated with soil available phosphorus.The results of variance analysis showed that soil factors and spatial distribution explained DSE colonization.3.A total of 16 species of DSE belonging to 11 genera were isolated and identified in A.ordosica,including Paraphoma sp.,Alternaria sp.,Cladosporium sp.,Chaetomium sp.,Fusarium sp.,Pleosporales sp.,Preussia sp.,Acrocalymma sp.,Periconia sp.,Trematosphaeria sp.and Trematosphaeriaceae sp..The dominant species were Paraphoma chrysanthemicola?Alternaria chartarum and Acrocalymma vagum,with the separation frequency of 52.48 %,9.93 % and 9.93%,respectively.4.The non metric multidimensional scale(NMDS)analysis of DSE community composition showed that there were significant differences in DSE community composition among different sampling sites,among which Dengkou had the most species of DSE fungi,followed by Alxa,Shapotou and Minqin.5.Different gradient PEG concentrations were set to simulate drought stress to explore the drought resistance mechanism of different DSE.Under the condition of solid stress,the hyphae showed darker color,shorter interval and wider hyphae,the color of some strains became white under high concentration.Superoxide dismutase(SOD),soluble protein,malondialdehyde(MDA),melanin content and biomass were determined under different drought stress liquid culture.With the increase of PEG concentrations,it showed that low osmotic potential promoted,high osmotic potential inhibited,promoted or unchanged,which indicated that different DSE strains had different ability to adapt to the drought.6.Three DSEs(A.chartarum,P.chrysanthemichola and A.vagum)isolated from A.ordosica were successfully inoculated to the host plant A.ordosica.It was found that DSE could colonize the root of A.ordosica and the plants could grow healthily.Under drought stress,DSE inoculation improved plant height,root length and biomass to a certain extent.DSE inoculation could reduce the content of proline and MDA,effectively alleviate the stress on plants,improve the ability of resistance to stress,which is of great significance to the restoration of desert vegetation.