| Cucumber Corynespora leaf spot caused by Corynespora cassiicola is one of the most serious and difficult to control disease in greenhouse cucumber production.At present,Corynespora leaf spot is mainly controlled by chemical fungicides,which cause fungicide resistance problems and cucumber phytotoxicity.Therefore,green control products are urgently needed.In this study,cucumber Corynespora leaf spot disease was used as the target,and a strain that belongs to Bacillus was screened and exhibited good antagonistic effect on C.cassiicola.At the same time,optimization of fermentation process and spary drying process of Bacillus amyloliquefaciens,development of micronized powder formulation,and field control effects research were conducted,and developed biological micropowder for Cucumber Corynespora leaf spot,successfully.The main results were as follows:1.Screened and identified a strain of Bacillus amyloliquefaciens,which had a significant control effect on the pathogen causing cucumber leaf spot.Soil samples were collected from areas with severe disease occurrence in Liaoning,Shandong,Hebei,etc.After isolation and purification,an antagonistic bacteria named ZF57 was screened by determination of the inhibitory effect on pathogens.The inhibitory activity of strain ZF57 on the Corynespora cassiicola was 64.85%.The result of antifungal activity of strain ZF57 tested by plate confrontation method showed that strain ZF57 exhibited a broad spectrum against seven pathogenic fungi.The control effect of ZF57 against cucumber Corynespora leaf spot by in vitro method,pot experiment and field test were 66.67%,58.73% and 66.67%,respectively.The strain of ZF57 was identified as Bacillus amyloliquefaciens based on morphology,physiological and biochemical characteristics,Biolog analysis and 16 S r DNA sequences analysis.ZF57 was domesticated with rifampicin resistance.The domestication process had no adverse effect on strain ZF57,and the domesticated strain named ZF57-rif could be used as a later test material.2.Optimized the medium composition,fermentation conditions and spray drying parameters of ZF57-rif.Based on the one-factor-at-a-time method and response surface analysis method,fermentation process was determined.Results showed that Bacillus amyloliquefaciens ZF57-rif fermentation broth increased by 80% under the optimal medium: sorbitol 10 g/L,cottonseed cake powder 17 g/L,Na H2PO4 0.5g/L?Na2HPO4 0.4g/L,p H 7.0;and culture condition: 80 m L medium in 250 m L flask,inoculum concentration 2.1%,30?,180 r/min,36 h.One-factor-at-a-time method was used to optimize the carrier,inlet temperature and carrier content used for spray drying.The best parameter was determined to be the inlet temperature of 160?,silica: diatomite = 1: 3 was used as the dry carrier,10%,the bacteria content of the dry matter was about 5 × 109 CFU/g.3.Screened a kind of nutritional auxiliary that can promote the colonization of biocontrol bacteria on cucumber,clearly understand the best formula of Bacillus amyloliquefaciens micropowder.50% of Bacillus amyloliquefaciens as active ingredient,29% diatomite as main carrier,10% silica as second carrier,4% sodium dodecyl sulfate as surfactant,1% sodium lignin sulfonate as dispersant,1% carboxymethylcellulose as protector,5% cottonseed cake powder as nutritional auxiliary.The Bacillus amyloliquefaciens micropowder had a particle size of 8.31 ?m and a dispersion index of 98.16%.The planktonic index was 86.26,water content was 1.42%,and the slope angle was 68°.The results were in line with standards.The control effect of Bacillus amyloliquefaciens micropowder in the field was 80.16%,which is higher than that of chemical fungicide. |
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