Spatiotemporal Distribution And Drought Promotion Of Dark Septate Endophytes Fungi In Lycium Ruthenicum In Northwest China

Lycium ruthenicum Murr is a perennial thorny shrub of Solanaceae,with strong biological characteristics of cold,drought,salt and alkali,is a natural wild medicinal plant and a pioneer shrub for water and soil conservation.Dark septate endophyte(DSE)is a kind of fungi that colonize root epidermis,cortex and vascular tissue.It has a wide range of host and ecological distribution characteristics and plays an important role in promoting plant growth and enhancing the stress resistance of host plant.In this study,the symbiotic relationship between DSE fungi and desert plant was taken as the entry point.Root and soil samples were collected from 0-30 cm of L.ruthenicum roots in 2019 and 2020,to systematically study the colonization structure,ecological distribution,species diversity and the relationship between DSE and soil factors.DSE fungi resources were isolated and conserved,excellent stressresistant DSE strains were screened,and DSE strains were inoculated to study the response of plant growth and drought resistance,so as to provide a basis for the growth of symbiotic fungi in L.ruthenicum and the restoration of desert vegetation and ecological restoration.The main results showed as follows:1.The root of L.ruthenicum can be highly infected by DSE fungi,forming typical dark septate hyphae and microsclerotia structures,and the colonization rate of hyphae was higher than that of microsclerotia.In different months of wild L.ruthenicum in 2019,the average total DSE colonization rate was July(70.00 %)> December(65.56 %)> September(44.08 %).In different sites,the total DSE colonization rate of Anxi plot was the highest(86.67 %),which was significantly higher than that of Shapotou(66.67 %),Dengkou(53.75 %)and Minqin plot(53.33 %).The seasonal variation of cultivated L.ruthenicum of DSE colonization was the same as that wild L.ruthenicum,average total colonization rate of DSE in July(68.89 %)> December(61.67 %)> September(40.00 %).2.The ecological distribution of DSE was significantly affected by different months and sites,and was closely related to soil factors.SEM structural equation showed that the colonization of hyphae was directly affected by sampling sites,and the colonization of microbacteria was directly affected by months.The colonization rate of hyphae was significantly negatively affected by soil p H and alkaline phosphatase(P < 0.001);The colonization rate of microsclerotia colonization was significantly positively with organic carbon(P < 0.001),and negatively correlated with alkali-hydrolyzed nitrogen(P < 0.001).3.The isolation rate and species diversity of DSE fungi of L.ruthenicum have temporal and spatial heterogeneity.In different months of wild L.ruthenicum in 2019,the isolation rate of DSE strains was as follows: July(24.00 %)> December(17.00 %)> September(16.00 %),the highest DSE Shannon Wiener index and Simpson index in July,and the highest DSE evenness index in December.In different sites,the isolation rate of DSE strains was as follows: Anxi(17.00 %)> Shapotou(9.00 %)> Minqin(7.00 %)> Dengkou(5.00 %),and Anxi plot had the most DSE species and Shannon Wiener index was the highest.The seasonal variation of species diversity of cultivated L.ruthenicum was different from that of wild L.ruthenicum,and the Shannon Wiener index and Simpson index were the highest in September.4.A total of 23 species of DSE belonging to 17 genera were isolated and identified in L.ruthenicum,all of which belonged to Ascomyces.The dominant species were Alternaria chlamydospore and Microascus alveolaris,with the separation frequency of 25.37 % and11.19 %,respectively.Neocamarosporium phragmitis,Papulaspora equi,Cyphellophora olivacea,Slopeiomyces cylindrosporus and Thermomyces verrucosus were reported here in desert ecosystems for the first time.5.In vitro Culture found that different strains of DSE of drought-resistance in different.Under solid stress culture,with the increase of stress degree,the diameter of DSE colonies decreased,and the space between hyphae became shorter or appeared a chlamydospore like structure.With the increase of MMN liquid stress,DSE strain showed the phenomenon of low osmotic potential promoting,high osmotic potential inhibiting,promoting or unchanged.6.The DSE fungi were successfully colonized in the root system of L.ruthenicum.Seedling growth was significantly affected by different DSE species,different water content and different environment.Inoculation N.phragmitis,A.chlamydospora and M.alveolaris all increased plant height,leaf number and total root volume.Inoculation A.chlamydospora only significantly increased aboveground biomass under drought stress,and inoculation N.phragmitis and M.alveolaris only significantly increased underground biomass under aseptic environment.7.Under drought stress,inoculation of DSE fungi can increase GSH content,SOD activity,proline and soluble protein content.Inoculation DSE can effectively alleviate the adverse effects of drought stress on plants.Inoculation A.chlamydospora increased GSH content,inoculation M.alveolaris increased malondialdehyde content,inoculation N.phragmitis and M.alveolaris increased auxin and chlorophyll content in aseptic environment.In this study,the colonization structure,ecological distribution and the relationship between soil factors of DSE fungi of L.ruthenicum were investigated by combining field sampling and laboratory experiments.PEG-6000 was used to simulate drought stress to screen excellent DSE strains,and to study the growth and drought resistance response of host plants in different pot experiments,so as to provide basis for breeding and cultivation of symbiotic fungi in L.ruthenicum and vegetation restoration and ecological reconstruction in northwest desert area.