Isolation And Identification And Interaction Promotion Of Growth Research Of Mycorrhizal Fungi From Wild Lingonberry

Endophytic fungi are widely present in lingonberry tissues and have obvious colonization characteristics in the roots,which can form special Ericoid mycorrhizal fungi(Er MF)structures and contribute to plant growth and environmental stability,and are one of the important components of the lingonberry root microbial community.Therefore,it is important to explore the probiotic strains and screen the combination of beneficial strains for the growth and development of cash crops such as lingonberry.In this study,we isolated root endophytic fungi from lingonberry(Vaccinium vitis-idaea L.)fibrous roots,screened strains using plant growth-promoting characteristics,analyzed their growth-promoting potential and enzymeproducing ability;explored the interaction of strains and the effect of strain inoculation on plants in vitro culture,screened beneficial strain combinations suitable for lingonberry growth.The experimental results were as follows:(1)Using the lingonberry fibrous roots in the Greater Khingan Range region as the experimental material,58 root endophytic fungi with different colony morphology were isolated.The isolated strains were identified morphologically and molecularly and classified into 2 families and 25 genera,of which Oidiodendron,Phialocephala,Lachnum and Fusarium have a high frequency of isolation and are the dominant taxa.The mycelial colonization of isolated strains was mainly divided into four forms,among which strain Arachnopeziza aurata M9,strain Oidiodendron maius M20 and strain Pezicula ericae M25 were representative strains that formed a typical Er MF structure.(2)Four strains were screened for their potential in vitro plant growth-promoting properties based on nitrogen fixation,phosphorus solubilization,potassium solubilization and siderophores-producing: strain Lachnum pygmaeum M8,strain Arachnopeziza aurata M9,strain Oidiodendron maius M20 and strain Peniophora sp.M21.Among the screened strains,strain M20 had the strongest IAA production capacity,reaching 9.42±0.02 μg/m L;strain M21 had the strongest phosphorus solubilization and iron carrier production capacity,reaching180.02±1.16 μg/m L and 62.74%,respectively.All the screened strains could produce cellulase,xylanase,polygalacturonase,protease and laccase activities;strain M20 produced the highest cellulase and protease activities,reaching 104.32±3.79 U/L and 31.55±0.05 U/m L,respectively;strain M21 produced the highest xylanase and polygalacturonase activities,reaching910.89±8.95 U/L and 178.44±9.42 U/m L,respectively;strain M8 produced the highest laccase activity,reaching 43.13±0.72 U/m L.The GFP gene was transferred into the fungal genome by Agrobacterium-mediated method and finally expressed successfully in the genomes of strains M8 and M20.(3)In the process of exploring the isolated interactions between strains,it was found that mycelium could contact each other and there was inhibition of mycelial growth,but the rate of mycelial inhibition was not high.Except for the soluble metabolites of strain M8,the metabolites of the other three strains promoted the growth of mycelium of all strains except themselves.Laccase,polyphenol oxidase,lignin peroxidase and chitinase activities of the four strains were affected by adding strains of inactivated mycelium as substrates.The inactivated mycelium of strain M8 was the best substrate to induce laccase and lignin peroxidase in the strain,which significantly increased the ability of other strains to secrete laccase and lignin peroxidase,and the polyphenol oxidase and chitinase activities were mutually promoted and inhibited among the strains.(4)Using lingonberry seeds,model plant tobacco and the fermentation broth of the screened strains as experimental materials,it was found that the fermentation broth of strains M9 and M20 had positive effects on the germination of lingonberry seeds and the growth of the model plant tobacco,in which the fermentation broth of strain M9 diluted 50 times was the best strain and concentration to promote seed germination and plant growth,while plant hormones such as IAA and CTK were analyzed in the fermentation broth of strains M9 and M20.Inoculation with mycorrhizal fungi significantly promoted the growth of lingonberry,and the best combination was co-inoculation with M9+M20.After 4 weeks of inoculation,the inoculation treatment significantly increased the photosynthetic pigment content,soluble sugar content,SOD,POD and CAT activities of the leaves compared to the uninoculated treatment,and co-inoculation significantly decreased the MDA content of the leaves compared to the single inoculation treatment;the single inoculation treatment decreased the soluble protein content of the leaves while the co-inoculation treatment increased the soluble protein content of the leaves.