Optimization Of Fermentation Conditions Of Bacillus Methylotrophic ZLS-3 And Its Controlling Effect On Corn Stalk Rot

Corn is one of the most important grains in the world,and it plays a vital role in global agriculture,human diet,animal feed,and cultural customs.However,corn stalk rot has seriously affected on corn production in recent years.Corn stalk rot is a widespread and destructive soil-borne disease.The occurrence of the disease had caused yield loss and quality reduction.The control of corn stalk rot has always depended on the use of resistant varieties and the application of chemical fungicides.However,breeding resistant corn varieties is time-consuming,and pesticides may pose a threat to humans and the environment.Many high-quality pesticides cannot be provided to growers due to high costs.Therefore,it is of great significance to find a safer and more effective biological control method to control corn stalk rot.In this study,a Bacillus methylotrophicus ZLS-3 with antagonistic activity against plant pathogens was isolated,and its fermentation conditions were further optimized.It was compounded with chemical fungicides and plant antagonists in the hope of becoming a chemical product reduction to control corn stalk rot,which will provides biological control new method:1.methylotrophicus ZLS-3 has high antibacterial activity against on Fusarium graminearum,F.verticilliodes and F.proliferatum.The inhibitory diameter can reach 1.67±0.03 cm,1.98±0.21 cm and 1.88±0.45 cm,respectively.2.In order to further improve the antibacterial activity of ZLS-3 against Fusarium spp.,the fermentation conditions of ZLS-3 were optimized,and the antibacterial activity of fermentation supernatant against F.verticilliodes,F.proliferatum and F.graminearum in vitro was used as evaluation index.The best carbon source was sucrose,nitrogen source was peptone,and inorganic salt was NaCl.The optimum fermentation conditions of ZLS-3 against F.graminearum,F.verticilliodes,F.proliferatum were sucrose 2%,peptone 4%,NaCl 1%;sucrose 2%,peptone 3%,NaCl 0.5%;sucrose 2%;peptone 4%,NaCl 1%,respectively by orthogonal test of three levels and three factor.3.To further test the antagonistic effect of biocontrol bacteria ZLS-3 on fusarium stem rot and the growth-promoting effect of ZLS-3 in corn plants.Through the greenhouse pot experiment,the control effect of strain ZLS-3 on stem rot was determined to be 37.39%.The plant height of corn in the treatment group with biocontrol bacteria ZLS-3 fermentation broth irrigation was increased by 22.12%,root length was increased by 13.11%,fresh weight was increased by 14.55%,dry weight was increased by 29.72%,and there were significant differences.The results showed that the biocontrol bacterium ZLS-3 has an antagonistic effect on F.graminearum and a growth-promoting effect on maize at the seedling stage.4.The laboratory virulence test results of chemical fungicides and plant inducers compounded with biocontrol bacteria showed that the EC50 value of pyraclostrobin against F.graminearum,F.verticilliodes and F.proliferatum was 2.07 mg/L,1.95 mg/L,1.09 mg/L.The EC50 of oligochitosan against the three Fusarium species were 5.14 mg/L,1.49 mg/L,and 0.54 mg/L,respectively.Therefore,according to the results of laboratory tests and comprehensive consideration of field experiments,the selected agents were pyraclostrobin and oligochitosan.The 4 g/L oligochitosan seed soaking treatment promoted the growth of maize seedling length,root length,fresh weight and dry weight to 33.14%,17.59%,20.93%and 14.81%,respectively.5.The field experiment showed that the combination of biological control fungus ZLS-3,chemical fungicide and oligochitosan could reduce the amount of chemical pesticides and effectively control corn stolk rot.