Screening And Control Efficiency Of Complex Bacteria Strains Against Tobacco Grey Mould

In the recent years, tobacco gray mold is a new disease during the survey of tobacco diseases in Guangxi. Chemistry control is still an important measure for controlling the diseases, but it is likely to cause drug resistance, environment pollution and other issues. As more and more antagonistic microorganisms have been founded, using them to control tobacco gray mould has a broad development prospects. Basing on the screening of the antagonistic bacteria against Botrytis cinerea, complex biocontrol agents were builded and their efficiency on controlling tobacco gray mould were measured. Furthermore, biocontrol mechanism of antagonistic bacteria was preliminarily explored. The study results obtained are shown as follows:1、 Seventy antagonistic strains and thirty-two nutritious competition strains against Botrytis cinerea were obtained firstly by mycelial growth from four hundred and seventy strains of endophytic bacteria in tobacco. Seventy-two strains with great spore germination inhibition rate were selected by the spore germination method. Twenty-seven biocontrol strains with great inhibition effect were selected to carry out secondary screening test by tobacco leaves tissues method, the test indicated that control efficiency of twelve strains against tobacco gray mould was over50%. The result of compatible reactions of seven strains showed that most of strains display compatiblity except strain Y98.2、 With the morphological observation,physiological and biochemical index determination results, the analysis of16S rDNA and gyrase subunit B (gyrB) gene sequences, strains G59, G81and Y11were identified as Bacillus amyloliquefaciens, strains Y88and Y141as fluorescent Pseudomonas.3、 Five strains mentioned above were combined differently with two strains or three strins or four strians. The combination of Y11and Y141was the best with the control efficiency of72.02%, yet the combination of Yl1, Y88, Y141and G59was the worst with control efficiency of42.41%. Mixed proportions of Y11and Y141were optimized to improve their control effect. The results show that the control effect of the ratio of2:1, which was75.68%, was higher than that of every single-strain and other proportions.4、The combination of Y11:Y141(2:1) was used to determine control effect of greenhouse experiment. Protective efficiencies of Y11+Y141(2:1), Y11, Y141and iprodione (300mg/L) were65.81%,57.91%,42.09%and94.66%, respectively, which were higher than treatment efficiencies of them, with59.51%,42.19%,34.50%and85.78%, respectively. The control efficiency of complex strian was better than that of single strain t.5、The extracellular metabolites of strain Yl1and Y141could inhibit the the growth of all test plant-pathogenic fungi differently. It is implied that Y11and Y141had broad-spectrum antimicrobial activities. Antifungal effect of the extracellular metabolites of two strains on Botrytis cinerea was better than that of the volatile metabolites. With the improvement of dilution ratio of extracellular metabolites, the growth inhibition force of hypha is gradually weakened. Two strains of volatile metabolites on hypha growth inhibition is weak, below50%. The extracellular metabolites of strain Y11and Y141could significantly change the hypha morphology of Botrytis cinerea with optical microscope.The hyphae of treatment were tubbiness and distortion, part of the plasma leakaged and cell wall folded.