Screening,Identification And Biological Activities Of Soybean Endophytic Fungi

Plant endophytic fungi are fungi that are parasitic in healthy plant tissues or organs.They not only complete almost all life cycles in the special environment within the host without causing disease,but also in the growth,development,metabolism,and evolution of the host.In the process,it co-evolved with it and played an important role.Glycine soja(Glycine soja)is a closely related species with many advantages such as strong reproduction,strong stress resistance,wide adaptability and high protein content.Endophytic fungi isolated from wild soybean generally have the characteristics of their host growth.Adapt to specific genes and metabolic pathways and products,and have a certain impact on the host.Isolation and screening of wild soybean endophytic fungi and analysis of their active effects are of great significance for the further development of wild soybean endophytic fungi resources with potential application value.In this study,the endophytic fungi of wild soybean were isolated by tissue separation method,identified by morphological characteristics and molecular biological identification methods;the strains with excellent resistance and growth promoting effect were screened by hydroponics test and subjected to single factor experiments and Orthogonal test was used to determine the optimal culture conditions.The components of probiotics and their effects on the cultivated soybeans were analyzed by means of ultrasonic crushing,rotary evaporation and extraction.The main results were as follows: 1.Separation and purification of wild soybean endophytic fungi.Forty-one strains of endophytic fungi were isolated from healthy wild soybean plants.24 strains,12 strains and 5 strains were obtained from roots,stems and leaves.25 strains were identified by molecular biology,10 of which were from stems.,13 species are from leaves,2 species are from roots and belong to Alternaria,Bipolaris sorokiniana,Chaetomium globosum,Pezizomycotina.2.Screening of active strains.The hydroponic method was used to screen the multifunctional active strains through the effect of the endophytic fungi fermentation broth of wild soybean on the growth and stress resistance of soybean seedlings.YD-09 strain is one of the more active strains;the growth of soybean seedlings treated with YD-09 strain fermentation liquid has a significant increase compared with the control group(P<0.05),and makes the soybean seedlings have significant Resistance to salt stress,cadmium stress and drought stress(P<0.05).3.Characteristics of YD-09 strain and optimization of fermentation conditions.The YD-09 strain is an Alternaria Nees filamentous fungus.The optimum fermentation conditions were as follows: PDA medium without carbon source as basic medium,lactose 4%,sodium chloride 1%,p H 7,temperature 28°C,liquid volume 50%,and fermentation at 120 rpm for 132 hours.4.The active ingredient of YD-09 strain.The active components of YD-09 strain were isolated by ultrasonic disruption,extraction,and rotary evaporation,and their activity was confirmed by hydroponics.The results showed that the extracellular macromolecule product had the ability to resist salt stress,and the intracellular small molecule product had Promote growth effect.5.Effect of Fermentation Liquid of YD-09 Strain on the Growth of Wheat Seedlings.The soluble protein content and SOD,POD and CAT activities of wheat seedlings treated with YD-09 strain fermentation liquid were significantly higher than those of the control group(P<0.05),and the contents of soluble sugar and MDA were lower than those of the control group(P<0.05).