The Species Diversity And Ecological Function Of Dark Septate Endophytes In Two Ecosytems Of Guangxi

Dark septate endophytes(DSE)are a miscellaneous group of root-colonizing microfimgi characterized by melanized cell walls or microselerotia and broadly intracellular colonizing of healthy plants,with broadly distribution and having ecological function as mycorrihizal fungi.In this study,DSE fungi from Dashiwei Tiankengs and sugarcane rhizosphere in Guangxi were isolated and identified;their population,richness,distribution and diversity were investigated;the plant growth promoting and disease resistant enhancing isolates were screened.The results of this study enrich our country's DSE resource bank and provide theoretic basis to use DSE biotechnology for agroecological environment protection.1.DSE isolation and identification.One hundred and twenty-one soil samples were collected from virgin forest of Dashiwei Tiankengs Group and sugarcane rhizosphere of five main sugarcane producing areas in Guangxi.Total 2562 isolates were obtained by using eggplant and Chinese cabbage as baiting plant.Ninety-four symbiotic DSE isolates were screened by disease test and microscopic examination.The isolation rate was 2.8%.According to the morphology and the sequence analysis of ITS,SSU and LSU regions of rDNA,the DSE isolates were classified as 94 taxa including 72 Ascomycota.Thirty-eight spore production isolates in 43 identifiable taxa were identified as 32 species of 19 genus.Eight new species including Conlarium nanningense,Conlarium sacchari,Conlarium baiseense,Piriformospora sacchari,Tetracladium botryospora,Tetracladium vietus,Ochroconis septispora and Dematipyriforma sacchari were discovered in this study.2.Frequency,distribution and diversity of DSE.The dominant classes were Sordariomycetes,Eurotiomycetes and Dothideomycetes;the dominant orders were Chaetothyriale,Pleosporales,Sordariales and Atractosporales,and the dominant generas were Cladophialophora,Conlarium,Cladosporium,Schizothecium,Podospora and Exophiala.The dominant species were Conlarium sacchari(5.4%),Chloridium virescens(2.2%),Dematipyriforma aquilaria(2.2%)and Cladosporium sphaerospermum(2.2%).The isolation rate of Hechi and Nanning were significant higher than the other three regions.The isolation rate of sugarcane rhizosphere was significant higher than Tiankengs.The dominant fungi of DSE communities harbored were significant different in five regions at order and genera level.The most dominant genera in Nanning were Conlarium,in Chongzuo were Conlarium and Cladophialophora,in Baise were Podospora,and in Hechi and Liuzhou were Cladophialophora.The dominant fungi communities was not significantly different between harbored in sugarcane rhizosphere and Tiankengs at orders level,but significantly different at genera level.Podospora,Schizothecium and Exphiala were the common dominant fungi in both habitats.Cladosporium,Conlarium and Cladophialophora were the specific dominant fungi,Cladophialophora was the most dominant fungi in sugarcane rhizosphere.There were various and abundant DSE community harbored in both habitats(S,74;H',4.32;1-D,0.99).The change law of species richness,Shannon-Wiener and Simpson's Diversity was unanimous.The a-diversity of DSE harbored in Nangning,Baise and Liuzhou was significantly higher than Chongzuo and Hechi,and no significantly different between two ecosystems.3.Plant growth-promoting effect of DSE.A sugarcane growth-promoting strain 26R-5 was selected by petri dish screening,pot-test and field experiment.The fresh weight and tillering number of sugarcane were significantly increase(42.1%and 31.4%,respectively.)with sweetness unchanged compared to control in field conditions after 11 months inoculated by this isolate.All strains could symbiosis with Dendrobium candidum after six months inoculation.Compared to control,the stem diameter,fresh weight and dry weight of Dendrobium candidum treatmented by strain 24L-4(Devriesia lagerstroem)in pot test was significantly increased 104.0%,83.9%and 114.7%,respectively.4.Biocontrol effect of DSE.The strain L-14(Schizothecium sp.)was selected,with high control efficacy to banana Fusarium wilt disease in dish culture(72.4%)and pot culture(56.5%)experiment separately,and plant height and fresh weight were significant increasing.It improved the banana seedling resistant to Fusarium wilt disease of by increasing the enzymes activity of phenylalanine ammonialyase,peroxidase,polyphenol oxidase and superoxide dismutase.