| In recent years,the bacterial angular leaf spot disease of cucumber has occurred severely,seriously affecting the yield of cucumber.In this thesis,we mainly screened the highly effective antagonistic strains of Bacillus velezensis ZF145 causing bacterial angular leaf spot of cucumber in order to obtain a Bacillus strain with good antagonistic effect on bacterial angular leaf spot of cucumber,and optimized the fermentation conditions and the development of micronized agent.Finally,a field application of the strain technology of Bacillus micropowder to effectively control bacterial angular leaf spot of cucumber was established.1.One strain of Bacillus with obvious inhibitory effect on the pathogen of bacterial angular leaf spot of cucumber was screened.With cucumber bacterial angular leaf spot as the target,the suspected antagonistic bacteria in cucumber rhizosphere soil were screened by the plate confrontation method and spray inoculation method,and a biocontrol bacteria ZF145 with obvious inhibitory effect was obtained.the strain ZF145 was identified as Bacillus velezensis through biochemical,Biolog determination and multi-gene sequence analysis.In vitro test of the plate,the inhibition zone diameter of this strain was 5.60 cm,and the inhibition rate was 62.22%.In the pot experiment and field experiment,the concentration of 1×10~8CFU/mL Bacillus velezensis ZF145 suspension was sprayed on the plants of cucumber.It has obvious control effect on cucumber bacterial angular leaf spot,on potted plant control effect is71.10%,in the field control effect is 61.30%.The plate confrontation method and the double-layer culture method proved that the strain ZF145can obviously inhibit the growth of 5 pathogenic bacteria and 8 pathogenic fungi,and has a relatively broad-spectrum antibacterial effect.In summary,the strain ZF145 has excellent biological control properties and is effective in plant disease organisms.There is a certain potential for application in prevention and treatment.2.The fermentation process of Bacillus velezensis ZF145was established.Through single factor experiment and orthogonal experiment,the best fermentation medium formula of Bacillus velezensis ZF145 was determined as follows:molasses 25 g/L,cottonseed meal 12.5 g/L,sodium chloride 0.2 g/L,p H=8.0;The most suitable fermentation conditions are:temperature 28℃,inoculation volume 4%,liquid volume 50 mL/250 mL Erlenmeyer flask,rotating speed 240 r/min,culture time 36～40 h.3.The formula of the micropowder of Bacillus velezensis ZF145 was clarified.Through the biocompatibility test and spray drying test to optimize the spray drying conditions,it was determined that the best carrier for Bacillus velezensis micropowder was diatomaceous earth,the IVF-42 was 10%,and the best air inlet temperature was 140℃,The injection rate is 25%.Through a single factor test,the formula of Bacillus velezensis Micropowder was determined as follows:mother powder 10%,IVF-A was 1%,IVF-D was 7%,stabilizer phosphate diphosphate Potassium hydrogen 2%,UV protectant dextrin 1%,IVF-24 was 15%,IVF-42 fill up to 100%.After mechanical pulverization and jet pulverization,it was developed into a micropowder.The wetting time was13.33 s,the suspension rate was 76.81%,the long-lasting foamability was39.17 mL,the particle size was 7.25μm,the moisture content was 1.11%,and the bacteria rate was 1.11%.0.64%,p H=6.59,all test results are in line with national standards.4.Established the field control technology of Bacillus velezensis micropowder on the bacterial angular leaf spot of cucumber.When the Bacillus velezensis micropowder was sprayed at 200 g/666.7 m2 under different environmental conditions,the control effect was more than 55%,which was significantly different from the control effect of spray treatment(46.23%).In addition,Bacillus velezensis and Bacillus velezensis ZF145can be detected on the plant on the first 1,3,5,7,10,15 days after spraying the 3×10~4CFU/g Bacillus velezensis micropowder in different environments.The powder has strong colonization ability. |
