Screening Of Antagonistic Bacteria Against Muskmelon Fusarium Wilt And Optimization Of The Fermentation Condition By Response Surface Methodology

Muskmelon fusarium wilt is a kind of fungal disease, which can influence quality and yield of muskmelon. Muskmelon fusarium wilt is controled by chemical agents, resistant varieties, agricultural control, etc., but these methods have shortcomings. Biological control was paid attention to as a control method of human and environmental safety, but there are few studies on biological control of F. oxysporum in tropical regions in China, and effective bio-control bacterium resources are limited, which limited the biological control technology development on the disease. This study will provide bio-control materials of F. oxysporum, at the same time enrich bio-control resources of F. oxysporum and promote the development of bio-control technology by screening strains with good control effect on F. oxysporum from Hainan soil.The preliminary results were as follow:(1)570strains were isolated from the soil samples collected from muskmelon and vegetable fields in the11counties in Hainan province. The strains D1、F1、H3showed strong antagonistic effect against Fusarium oxysporum by adopting plate confront culture method and promoted the germination rate of musketmelon seeds. which were strong antagonistic effect against F. oxysporum and no adverse effect on muskmelon seeds. Meanwhile the control effect of strains D2and F1were73.5%and70.6%in potted plant experiment, respectively.(2)Based on phenotypic characteristic and16S rDNA sequence analysis,D2was identified as streptomyces and Fl was Bacillus methylotrophicus.(3)The experimental model by response surface methodology optimization strain D2fermentation conditions was:Y=8.28757+0.12344×X1+0.21477×X2+0.06184X X3-0.05929×X12-0.09817×X22-0.14942×X32, the optimal fermentation conditions: the content of corn flour was39.08g/L, the content of bean cake powder was39.19g/L, incubation temperature was37.4℃, the theory of the effective number of living bacterium was3.01×10cfu/mL. The experimental model by response surface methodology optimization strain F1fermentation conditions was: Y=3.48334+1.24919X X1-0.47420X X3-0.01084X X12-0.89805X X22+0.01479X X32+0.09369×X1×X2-0.03812X X1×X3+0.12490×X2×X3, the optimal fermentation conditions:the content of mineral salt was3.93g/L, incubation temperature was30.0℃, the theory of the effective number of living bacterium was1.51×109cfu/mL.(4) Two strains D2and F1of The effective numbers of living bacterium were close to the theory effective numbers of living bacterium in the optimal condition, which showed that it was feasible to optimize fermentation conditions of D2and F1by response surface methodology.