Mycobiota Composition Of Root Endosphere And Effects On Seed Germination And Plantlets Growth Of Bletilla Striata

Bletilla striata is a Orchid widely distributed in our country with high ornamental value,economic value and medicinal value.Due to the uncontrolled excavated and ecological environment damaged severely,the amount of wild resources has been reduced year by year.At present,Bletilla striata can be cultivated artificially,but it lacks symbiotic fungus,the transplanted seedlings have low survival rate and growth slowly,which restricted the industry development of Bletilla striata.Therefore,it is necessary to isolate root endosphere and screen out the isolates with germinating and growth promoting effects through symbiosis experiments,so as to realize industrial production of Bletilla striata.The section isolation method was applied to isolate root endosphere from the root of Bletilla striat.After blasting the ITS sequences of isolated fungi in NCBI database,the annotation of the closest matched sequences were used to analyse root endosphere mycobiota composition and ecological function.The fungi with symbiotic troph mode were utilized for further symbiotic germination experiments to select the fungal isolates with promoting effect on seed germination and tissue culture seedling growth of Bletilla striata.And microscope observation was conducted to confirm whether the isolates were mycorrhizal fungi.Main results are as follows:(1)Consequently,246 fungal isolates were isolated,including 62 OTUs,belonging to 3 phyla,6 classes and 16 orders,10,5 and 1 of which affiliated to ascomycetes,basidiomycetes and Zoopagomycota.62 OTUs could be assigned to 3 trophic types including symbiotroph,saprotroph and pathotroph,respectively;and 9 guilds,including ectomycorrhizal,undefined saprotroph,plant pathogen,lichen parasite,endophyte,wood saprotroph,dung saprotroph,soil saprotroph and plant saprotroph,respectively.(2)9 fungal isoltes had significant promoting effect on seed germination compared to the control,and 7 of those,including 3 Sebacina,3 Serendipita,and 1 Tulasnella isolate,respectively,were mycorrhizal fungi colonizing protocorms in the form of pelotons;2 of those,including 1 Acremonium and 1 Chaetomium isolate,respectviely,were non-mycorrhizal fungi with no pelotons in protocorms.Sebacina isolate WN18-2-18 had the most significant promoting effect on seed germination.(3)The isolates with seed promoting effect were co-cultured with tissue culture plantlets of Bletilla striata,and the symbiotic culture medium for Bletilla striata tissue culture plantlet was peat medium,and the inoculation modes was liquid strains to promote whitening and seedling growth was better.The isolates with promoting effect on Bletilla striata tissue culture plantlet growth were WN18-4-26,WN18-2-18,WN18-4-25 and WN18-3-9,which belonged to Cladosporium sp.? Sebacina sp.?Tulasnella sp.?Acremonium sp.,respectively.