Shaanxi Greenhouse Melon Three Major Fungal Diseases In Biological Control

Nowadays Melon fusarium wilt,Melon downy mildew and Melon powdery mildew are the most serious diseases in many melon-growing areas in China, decreasing the yield and quality of melon.Aimed on obtaining the broad-spectrum antagonistic strains and exploring a green, efficient, sustainable control methods towards melon three main diseases, the present study was undertaken in antagonistic Bacillus stains screening, identification, optimization of fermentation process and pot experiment.245 bacterial strains were isolated from rhizosphere soil, yak dung, and vermicompost, 14 out of which were revealed antagonistic effect on the pathogen of Melon fusarium wilt (Fusarium oxysporum f. sp. melonis) in the plate confrontation assay and plate-well tests. Strain FCJ2 was screened out from the 14 strains with strong inhibition activities on the pathogens of Melon powdery mildew (Sphaerotheca cucurbitae (Jacz.) Z.Y.Zhao) and Melon downy mildew (Pseudoperonospora cubensin (Berk.et curt).Rosto). Its inhibition rate of the fermentation broth of was 64.7% on Fusarium oxysporum f. sp. melonis, and the inhibition rate of spore germination was 62.3% on Sphaerotheca cucurbitae (Jacz.) Z.Y.Zhao, 49.2% on Pseudoperonospora cubensin (Berk.et curt).Rosto.Based on morphologic, physiological, biochemical characteristics and 16S rRNA sequence analysis, strain FCJ2 and Bacillus subtilis was closest relative with 99.99% sequence similarity.Considering viable count in fermentation broth, the orthogonal method test was used to find the optimal fermentation medium. The results showed that the optimal fermentation medium contained diastase 2.00g, soybean meal 2.00g, protein peptone 0.30g, yeast extract 0.20g, Corn Starch 2.00g. And the significance of these factors was soybean meal> diastase> yeast extract> protein peptone> yeast extract. The orthogonal method test showed that the favorable fermentation condition was determained:temperature 30℃, original PH 6.5, pack amounts 25ml volume medium in 250ml triangle bottle, inoculation quantity 7% and shaker rotation speed 200r/min. The significance of these factors was shaker rotation speed> inoculation quantity> original pH> temperature> pack amounts.In biocontrol assays in potted plants, strain FCJ2 showed 88.5% control efficacy on Fusarium oxysporum f. sp. melonis,93.6% on Sphaerotheca cucurbitae (Jacz.) Z. Y. Zhao and 82.6% on Pseudoperonospora cubensin (Berk.et curt) Rosto respectively. Compared with the pesticides treated group, the test group appeared significantly increased control efficacy (p<0.05).