Study On The Preparation Of Bio-organic Fertilizer For Cucumber Wilt Disease And Its Control Effect

Cucumber Fusarium wilt is one of the most harmful soilborne diseases in cucumber cultivation.One of the main reasons for this disease is the deterioration of soil microbial community structure,the decrease of beneficial bacterial consortia,and the increase of pathogenic bacterial consortia caused by continuous cropping.Biological control is the most valuable and environmentally protected measure.The research shows that functional microorganisms and nutrients contained in bio-organic fertilizer can regulate soil physicochemical properties,and microbial community structure and control crop diseases and insect pests.This study aimed at the biological control of cucumber Fusarium wilt.Through the screening of functional strains,the development of bio-organic fertilizer,and field trials,the following main results were obtained:1.Over the years,the research group has isolated several Bacillus and Actinomycetes with good physiological activity from the saline-alkali soil of the Hexi corridor.We selected 4 strains with strong antagonism and growth-promoting effects,including strain 7-3-14（Bacillus endophyticus）and 4-2-1（Streptomyces leeuwenhoekii）can secrete indole acetic acid;strain PB2（Bacillus tequilensis）has the ability of phosphate and potassium solubilization;strain 17-2-1（Bacillus velezensis）has the ability of organophosphates solubilization.The four strains have good affinity and broad antibacterial spectrum,among which the inhibitory rate of strain 7-3-14 to Fusarium oxysporum f.sp.cucumerium,the pathogen of cucumber Fusarium wilt,reached 75.64%.2.Soil incubation experiments showed that bio-organic fertilizers with mushroom residue,sheep manure,and chicken manure as carriers can soil microbial community structure and increase soil fertility.Among them,the relative abundance of Firmicutes increased by 9.36%and Ascomycota decreased by 40.00%after the application of mushroom residue bio-organic fertilizer.Soil p H decreased by 0.58,available phosphorus,hydrolyzable nitrogen,electrical conductivity,and available potassium increased by 496.67μS·cm^-1,127.40 mg·kg^-1,40.03 mg·kg^-1 and 25.17 mg·kg^-1,respectively.Soil sucrase and urease activities increased.3.The effective number of viable bacteria in mushroom residue bio-organic fertilizer was 249 million·g^-1.Under the laboratory conditions,the inhibitory rate of F.oxysporum f.sp.cucumerium was 91.55%.In the field experiment,the application of mushroom residue bio-organic fertilizer can enrich the composition of the soil microbial community.At the phylum level,the relative abundance of Actinobacteria and Firmicutes increased,while the abundance of Ascomycetes decreased.At the genus level,Bacillus and Actinomyces’relative abundance increased,while Fusarium’s abundance decreased.It can significantly enhance soil fertility,in which available phosphorus,hydrolyzed nitrogen,and electrical conductivity increased by 45.38 mg·kg^-1,58.80 mg·kg^-1,and 52.66μS·cm^-1,respectively.Soil sucrase and urease activities increased.After the application of bio-organic fertilizer of mushroom residue,the incidence of cucumber Fusarium wilt decreased by 53.33%,and the control rate was61.54%,which significantly improved the relative chlorophyll content,plant height and yield of cucumber.4.Correlation analysis showed that the relative abundance of Actinomycetes was significantly correlated with soil conductivity and negatively correlated with Fusarium.The relative abundance of Fusarium was significantly negatively correlated with soil conductivity,catalase activity,and hydrolyzed nitrogen.The incidence rate was significantly negatively correlated with the hydrolyzed nitrogen and relative content of chlorophyll.The fungal diversity index was significantly positively correlated with the incidence rate and relative abundance of Fusarium.RDA analysis showed that soil urease and available phosphorus were positively correlated with the relative abundance of Bacillus and Actinomycetes.5.The KEGG database predicted the functional enzyme genes involved in nitrogen cycling,and the results showed that the absolute abundance of soil nitrogen cycling-related functional enzyme genes increased,among which the absolute abundance of genes for functional enzymes associated with nitrification amo A（K10944）,hao（K10535）and genes related to functional enzymes for nitrate assimilation nar B（K00367）,nas A（K00372）,nas B（K00360）and nir A（K00366）increased.The nitrate and nitrite anabolic reductase system（Nas）present in the cytoplasm is vigorous.In summary,four strains with excellent growth-promoting and antagonistic abilities were isolated from saline-alkali soil.Taking these four strains as the starting strains,it was found that mushroom residue was the best nutrient carrier through soil culture experiments.In the field experiment,mushroom residue bio-organic fertilizer has a good control effect on cucumber Fusarium wilt,which can effectively reduce the abundance of pathogenic bacterial consortia in soil,increase the abundance of beneficial bacterial consortia,adjust the soil physicochemical properties and microbial community structure of the soil,and improve the related physiological indexes of cucumber.