Species Diversity And Drought Resistance Of Dark Septate Endophytes In The Rhizospheres Of Different Plants In Anxi Extreme Arid Desert

Dark septate endophytes in the rhizospheres of five typical desert vegetations in Anxi Extreme Arid Desert of the National Nature Reserve,Gansu Province were chosen in our study,which included Ephedra przewalskii,Reaumuria soongorica,Sympegma regelii,Nitraria sphaerocarpa and Salsola passerine.Soil and root samples were randomly collected from the rhizospheres of the five target plants in July 2015 and 2016.Researches of species diversity and drought resistance of dark septate endophytes in the rhizospheres of different plants were conducted and their correlations with edaphic variables were discussed.This study provided a basis for further understanding the ecological functions of DSE and their roles in the promotion of vegetation restoration in extreme arid ecosystems.The main results were listed as follows:1.A total of 19 species of DSE belonging to 10 genera were isolated and identified in 2015 and 2016,and 6 of them were spore-producing species.The genera were listed as Alternaria,Aporospora,Embellisia,Thielavia,Darksidea,Paraphoma,Sarocladium,Podospora,Curvularia,Leptosphaeria.Darksidea zeta,Aporospora terricola,Alternaria alternata,Embellisia astragali,and Sarocladium implicatum were reported as DSE for the first time in the desert ecosystem.2.The Bray-Curtis similarity coefficients of DSE composition among the five target plants varied significantly.Except for that of S.passerine and S.regelii,the similarity of DSE composition among other plants was relatively low or even showed no similarity.Most of DSE strains showed host preference rather than specificity in the symbiotic relationship with their host plants.3.Principal component analysis showed that urease,ammonia nitrogen,total phosphorus and soil pH were main factors indicating soil nutritional status in Anxi Extreme Arid Desert of the National Nature Reserve.4.The isolation rate and diversity indexes of DSE from different plants were significantly different.The variation trend descended in the following order: S.passerine > E.przewalskii > S.regelii > N.sphaerocarpa > R.soongorica.Correlation analysis showed that Shannon-Wiener index was positively correlated with Simpson index and Pielou index,and all of them were positively correlated with ammonia nitrogen,urease,Olsen P while negatively correlated with acid phosphatase.5.Redundancy analysis showed that Aporospora and Paraphoma abundance were positively correlated with total nitrogen and total phosphorus respectively.Thielavia and Embellisia abundance were positively and significantly correlated with acid phosphatase and urease respectively.Alternaria abundance were positively correlated with soil organic matter.6.Curvularia lunata,Alternaria alternata,Pleosporales sp.,Sarocladium implicatum,Curvularia spicifera and Alternaria burnsii were predominat DSE strains with drought-resistant abilities in extreme arid desert.Melanin,SOD and CAT were main indicators reflecting drought-resistant abilities of DSE against arid enrironments.