Study On Mutation Breeding Of Antagonistic Bacterium Ata28 Strain Against Tobacco Brown Spot

Tobacco brown spot caused by Alternaria alternata(Fries)Keissler is an important fungal disease on the crop worldwide and makes large economic losses in tobacco maturation period. Presently pesticides is the major measure of controlling the disease, but the use of pesticides is restricted because this may induce problems as fungicide resistance and chemical residues in the environment. Biocontrol may be an alternative to avoid these problems in tobacco disease control. Ata28 strain is an antagonistic bacterium against tobacco brown spot was isolated from healthy tobacco in Chongqing. Ata28 strain exhibited marked suppression of Tbs3 strain which is the pathogen of tobacco brown spot on PDA plates, and the Ata28 strain had the good control efficiency of tobacco brown spot.In this study, as a original strain, antagonistic bacterium Ata28 was mutated by UV, UV+LiCl, DES and Microwave irradiation; the very goal of the research is to improve the control efficiency of Ata28 strain against tobacco brown spot and obtain strains advanced both in antagonism and biological characteristics, further provides theoretics and practical experience to the production.1.Ata28 strain was mutated by UV with the most optimum mutant time, including 10, 20, 30s, that was chosen by the trial tests, considering the lethality rate and positive mutation rate of Ata28; it was found that 15 mutant strains were shown antagonism against Tbs3 strain by antagonism test on PDA plate, inhibition zone of mutant strains exceeded the original strain Ata28, and the maximum of inhibition zone reached 9.4mm; the mutant strain Uv-126 was found most effective in tobacco brown spot control and a rate of efficiency control reached 52.2% on tobacco plants three days after bacteria spraying.2.Ata28 strain was mutated by UV+LiCl with the most optimum mutant time, including 15, 20s, that was chosen by the trial tests, considering the lethality rate and positive mutation rate of Ata28; it was found that 8 mutant strains were shown antagonistic against Tbs3 strain by antagonism test on PDA plate, inhibition zone of mutant strains exceeded the original strain Ata28, and the maximum of inhibition zone reached 9.7mm; the mutant strains Uvl-190, Uvl-199 were found most effective in...