Study On The Difference Of Rhizosphere Soil Microorganisms And Their Antagonism Against Fusarium Oxysporum Of Cucumber Varieties

Cucumber(Cucumis sativus L.)is a widely cultivated vegetable cash crop.With the increase of cucumber planting scale and continuous cropping in recent years,soil-borne diseases have become increasingly serious,especially cucumber Fusarium wilt.There is a certain relationship between the difference of rhizosphere soil microorganisms of different crop varieties and the disease resistance of crops.In this study,rhizosphere soil microorganisms of different cucumber varieties planted in different soils were isolated and identified,and their microbial community diversity was compared and analyzed by high-throughput sequencing technology.The antagonistic effect of isolated and cultured rhizosphere soil microorganisms against Fusarium oxysporum f.sp.cucumerinum(FOC)was evaluated by plate confrontation method,and the growth-promoting ability of these microorganisms was determined,and the rhizosphere soil microorganisms with better antagonistic and growth-promoting effect were obtained.The effects of these antagonistic rhizosphere soil microorganisms on cucumber growth and control of cucumber Fusarium wilt were evaluated by indoor pot experiment.The specific research results are as follows:There are obvious differences in rhizosphere soil microbial community structure among different varieties and soils,but the results of plate separation and identification are different from those of high-throughput sequencing.The results of plate separation and identification showed that the diversity of rhizosphere soil microbial community structure of Longyuan Xiuchun and Shengqiu 2 varieties with relatively high resistance was higher than that of Shuyan2 varieties with relatively low resistance,while the results of high-throughput sequencing showed that the diversity of rhizosphere soil microbial community structure of Shuyan 2varieties was slightly higher than that of Longyuan Xiuchun and Shengqiu 2 varieties.The results of plate confrontation showed that 10 antagonistic strains against Fusarium oxysporum f.sp.cucumerinum were screened out from 78 strains of rhizosphere soil microorganisms,among which Pseudomonas aeruginosa LH-10 and Bacillus subtilis LD-15 had the most obvious antagonistic effects,and their bacteriostatic rates were 65.2% and 67.5%,respectively.Bacillus cereus LD-3 and QD-1,Bacillus altitudinis LH-3,Bacillus thuringiensis QD-15,Pseudomonas chlororaphis LD-16 and LH-11,Streptomyces netropsis LD-13 and Haemophilus huttiense QH-15 also had good antagonistic effects,and the bacteriostatic rate was 38.9% to 58.4%.The growth-promoting potential of 10 antagonistic growth-promoting bacteria was evaluated by measuring the abilities of ammonia production,nitrogen fixation,phosphorus dissolution,siderophore production and IAA production.The results showed that Pseudomonas aeruginosa LH-10,Bacillus subtilis LD-15 and Bacillus thuringiensis QD-15 had various growth-promoting abilities and had strong growth-promoting potential.Among them,LH-10 and LD-15 have the ability to produce ammonia,nitrogen fixation,phosphorus dissolution,siderophore and IAA production;QD-15 has the ability to produce ammonia,nitrogen fixation and siderophore production,it does not have the ability to dissolve phosphorus but has a strong ability to produce IAA.Pseudomonas aeruginosa LH-10,Bacillus subtilis LD-15 and Bacillus thuringiensis QD-15 were selected to treat cucumber seeds with bacterial suspension,and the effect of antagonistic growth-promoting bacteria on cucumber seed germination was evaluated by seed germination test.The results showed that different concentrations of LD-15,LH-10 and QD-15 could promote cucumber seed germination and root growth,and the mixture of LH-10 and QD-15 had the most remarkable growth promoting effect.Furthermore,the effects of antagonistic growth-promoting bacteria on cucumber growth and control of cucumber Fusarium wilt were evaluated by pot experiment.The results showed that LH-10,LD-15 and QD-15 all had good disease prevention and growth promotion ability in pot experiment,among which the mixed treatment of LD-15 and LH-10 had the most significant disease prevention effect,with the control effect of 73.91%,which was higher than that of single antagonistic liquid treatment.The mixed treatment of QD-15 and LH-10 has the most significant effect on cucumber growth,and significantly increased the plant biomass.