| The banana fusarium wilt caused by Fusarium oxysporum f.Cubense(FOC)is an important disease on bananas,which has caused great harm to the banana industry in China and the world.Fusarium oxysporum f.Cubense race 4 with its wide range of hosts,disease and other characteristics of a strong focus on prevention and control of the object.The current chemical control and other methods and can not be a good control of the disease,and environmentally friendly biological control has great potential,there are already some Bacillus as a commercial bacteria was successfully developed.In this study,the strain of Bacillus amyloliquefaciens ZJ6-6 was isolated and analyzed.The morphological changes of Foc4 and the internal changes of Foc4 were observed by scanning electron microscopy and transmis sion electron microscopy.The pot experiment was used to study the effects of ZJ6-6 on Foc4(P <0.05).The expression of biocontrol gene in fermentation broth was detected by fluorescence quantitative PCR.The liposomal antibiotics in ZJ6-6 fermentation broth were analyzed by LC-MS.The mechanism of lipopeptide antibiotic produced by strain ZJ6-6 and the mechanism of action to Foc4 were studied,which provided a theoretical basis for the development of a new commercial biocontrol.The results are as follows:(1)strain ZJ6-6 and Foc4 plate confrontation culture,the Foc4 have a better inhibitory effect,inhibition zone diameter of 15.3mm,antibacterial rate of 69.4%.After 5 days of confrontation,the abnormalities of Foc4 hyphae were observed by scanning electron microscopy and transmission electron microscopy.The number of mitochondria was significantly decreased,indicating that ZJ6-6 had a significant effect on the cell metabolism of Foc4 A certain degree of influence.(2)Pot experiment showed that strain ZJ6-6 could significantly reduce the incidence of Foc4 infested powdery banana,and the disease index was 57.2 and 85.6 respectively.The average plant height and fresh weight were 21.7cm and 62.5g respectively.The average plant height and fresh weight of the control group were 15.8cm and 43.6g respectively.The plant height and fresh weight of the plant were significantly increased,indicating that ZJ6-6 In addition to the effective control of Foc4,but also to promote plant growth.(3)The eight genes related to the synthesis of lipopeptide antibiotics were amplified by PCR: ituD,bmyB,fenD,srfAA,srfAB,bioA,ynd J,yngG,and can be amplified to the target band,Quantitative PCR was used to detect the expression of these genes at different time points in the fermentation broth.The results showed that the expression of these genes increased significantly in 16-24 h,and the expression of these genes was significantly different at different time points.(4)After LC-MS analysis,it was proved that the crude extract of strain ZJ6-6contained liposin antibiotic surfactin,and the detected mass-to-charge ratio(m / z)was near 1008,1022,1036 and 1050,It is speculated that the crude extract of lipopeptide may contain C13-15 SurfactinA,C14-16 SurfactinB or C16 SurfactinC.In addition the fermentation broth can also detect the corresponding lipopeptide substances,but significantly less than the lipid peptide crude extract content.And 1 day,2 days,3 days at three time points,1 day with 2 days,each Surfactin homolog content has increased,but the change is not significant.After 3 days of fermentation,the content of lipopeptide in the peak area of No.2 increased with the peak area of 5,which was significantly different from that of fermented day.The content of lipopeptide corresponding to 4 was decreased,but the difference not significant. |
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