Screening Of Multifunctional Bacteria In Tomato Rhizosphere And Preparation Of Their Fungicides

Tomato is one of the most widely cultivated fruits and vegetables in the world.In recent years,in order to improve the yield and quality of tomato,biological bacterial fertilizer is used in the production process.Biological bacterial fertilizer contains a large number of microbial functional bacteria,which can promote the release of soil nutrients and improve soil structure.Functional bacteria can also grow and reproduce in large numbers in plant roots,play a barrier role against other pathogens,enhance plant disease resistance,and metabolites can promote plant growth and development.In this thesis,multifunctional strains were isolated and screened from tomato rhizosphere,and their growth promoting effect and antagonistic effect on Fusarium graminearum were studied.1.A total of 85 strains of bacteria were isolated from tomato rhizosphere soil and plant interior by indirect isolation method.Among them,7 plants had IAA secretion characteristics,accounting for 8.23% of the total plants.The dissolution of phosphorus by 7 IAA producing strains was studied.It was found that 5 strains had the characteristics of dissolving organic phosphorus.The growth promoting effects of seven IAA producing bacteria on tomato and potato seedlings were studied by root irrigation method.It was found that the dominant strain fqd47-2 had obvious growth promoting effect on tomato and potato seedlings.The fresh weight of above ground and underground parts of tomato seedlings increased by 16.91%,29.58% and 67.09% respectively,the fresh weight of above ground and underground parts of potato seedlings increased by 17.64% and 15.26%respectively,and the dry weight of above ground and underground parts increased by12.70% and 15% respectively.The results showed that strain fqd47-2 had the characteristics of protease production.Through morphological identification,physiological and biochemical identification and 16 Sr DNA molecular biology identification analysis,it was proved that strain fqd47-2 was Bacillus aryabhattai.2.Using 85 strains of tomato rhizosphere and endophytic bacteria as test strains,the strains with antagonistic effect on Fusarium graminearum were screened by two-point confrontation method.The results showed that 6 strains had inhibitory effect on Fusarium graminearum.Fqd25 and fqc7 strains were selected for the antibacterial experiment of fermentation broth against Fusarium graminearum.The results showed that the bacteriostatic effect of fqd25 fermentation broth was greater than that of fqdc7,and the bacteriostatic rates were 36.42% and 26.49% respectively.The inhibitory activities of fqd25 fermentation broth on four pathogens(stephylium solani Weber,Fusarium oxysporum,Rhizoctonia solani and Fusarium brachygibbosum)were further studied.The results showed that fqd25 fermentation broth had different degrees of inhibitory effects on all four pathogens,and the inhibitory effect on Solanum solani was the largest,up to100%,The inhibition rate against Rhizoctonia solani was 67%,and the inhibition rate against Fusarium oxysporum was 37%.It had no inhibition effect on Fusarium brevis,but the colony color changed and there were few surface hyphae after fqd25 fermentation broth treatment.3.The protein of sterile fermentation broth of strain fqd25 was precipitated by ammonium sulfate with different saturation,and the inhibitory activities of ammonium sulfate extract under different concentrations on three different pathogenic fungi were measured.The results showed that the crude protein extract with different saturation had inhibitory activities on stolonium solani and Fusarium oxysporum,but had no inhibitory effect on Rhizoctonia solani,The inhibition effect on Fusarium oxysporum was the best when ammonium sulfate was 50% saturation,and the inhibition effect on Solanum stolonifera was the best when ammonium sulfate was 70% saturation.4.Strain fqd25 was preliminarily identified as Bacillus velezensis by colony morphology observation,physiological and biochemical identification and 16 Sr DNA molecular biological identification analysis.5.Strain fqd25 has the function of hydrolyzing organic phosphorus and inorganic phosphorus and producing protease.It can grow normally on ashaby nitrogen-free medium,and an obvious aperture can be formed on protease,organic phosphorus lecithin medium and inorganic phosphate rock powder medium.It is resistant to tetracycline and streptomycin.The bacteria can be seen in the two antibiotic media 24 hours after shaking table culture.The experimental study on the control of potato Fusarium wilt by strain fqd25 showed that the soil treatment of strain fermentation broth could significantly inhibit the occurrence of potato Fusarium wilt.The disease index of fqd25,carbendazim and clear water were 50,59 and 85 respectively.The control effects of fqd25 fermentation broth and carbendazim were 41.17% and 30.58% respectively.6.Preparation of wettable powder of strain fqd25.The carrier,dispersant,wetting agent and stabilizer were screened by taking strain activity,wetting time,suspension rate,drying loss and miscellaneous bacteria rate as indicators.The best ratio of carrier additives was determined,and the quality of wettable powder was tested.Through the evaluation of suspension rate,wetting time,water content and other indicators,the results showed that experiment No.4 performed best,with 251 colonies,75.9% suspension rate,22.83 s wetting time,0.40% miscellaneous bacteria rate,p H 6.22,0.1% water content,9.33 mm diameter of inhibition zone against Fusarium graminearum The width of the inhibition zone against the pathogen of tomato gray leaf spot disease was 16.33 mm.Finally,the formula of strain fqd25 wettable powder was determined as follows: Kaolin40%,peg8000 3%,Tween 80 6%,polyethylene glycol 5%,sucrose 1.5%,and the rest was supplemented by fqd25 fermentation broth with bacteria.