Identification, Optimization Of Fermentation Conditions And Application Of Antagonistic Bacteria (48SJ7-1) For Control Of Corn Stalk Rot

Corn stalk rot, caused by Fusarium graminearum, is a serious soil-borne disease in corn production worldwide, and become increasingly serious in China. We currently control the disease mainly by chemical control. However, the pollution, residue and health threat to human caused by fungicides are attached more attention on the increasingly awareness of environmental protection. Bio-control is a sustainable way to suppress populations of diseases, which draw the concerns of many scientists.Fusarium graminearum is one main pathogen of maize stalk rot. It was screened an effective biocontrol bacteria(named as 48SJ7-1) from widely planting corn varieties to control the pathogen in this study. This dissertation’s work mainly includes(1) the identification of the bacteria;(2) improvement of the culture conditions of bacteria; and(3) mechanisms of antagonistic bacteria and its field application.Firstly, the 48SJ7-1 was determined as a strain of bacillus methylotrophicus according to its physiochemical property, 16 SrDNA sequence and phylogenetic status.Secondly, the results showed that the best culture conditions were temperature-34.64℃, initial pH-7.39, incubation time- 25.78 h and inoculation concentration-1.64% in the fermentation process according to analysis of single factor experiments and response surface central composite design. And orthogonal experiments had been applied for designing of experiments to evaluate medium components. The perfect combination of culture medium was yeast extract-6 g/L, lactose-20 g/L and MgSO4-100 mg/L.Thirdly, the secondary metabolism substances of 48SJ-7 has a good inhibition effect to mycelial growth and spore germination of Fusarium. graminearum. And the protein precipitated by 50%~60%(not contain 60%) saturation ammonium sulfate has stronger antagonistic activity, which implied more antagonistic proteins and many kinds of antagonistic substances.To explore the potential of the bacteria’s application, pot experiments were conducted, and results showed that every treatment could reduce the disease incidence of maize stalk rot, the control efficacy of 48SJ7-1(1×109 CFU/mL 7 mL) was 68.47%, which was no significant difference with the control fungicide(2% tebuconazole FSC for 600 g/100 kg seeds). Field experiments were conducted in 2013 and 2014 to evaluate the efficacy of 48SJ7-1 for reduction of corn stalk rot., 48SJ7-1 was applied as root drench at different rates. Application of 48SJ7-1 reduced incidence of corn stalk rot by 74.45% and 78.72% in 2013 and 2014, respectively, which was not significantly different from the standard chemical fungicide tebuconazole. The potting and field results also showed that the 48SJ7-1 was benefit to maize growth, and no phytotoxicity was observed in the experiments.