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258 bacterial strains were isolated from 15 categeries collected from Hainan bananas, rubber and papaya soils.It has been screened for five strains with good antagonistic effect.S13 strain and S30 were identified as Bacillus cereus and Bacillus megaterium respectively,while S19,S29 and S40 were all identified as Bacillus subtilis.The growth conditions of strain 40 was done on experiment, the relative optimum growth temperature was 30℃-37℃, the relative optimum growth PH was 6-8. The largest quantity of bacteria arrived when the temperature come to 30℃-33℃. The largest quantity of bacteria arrived when pH was 7-8.It has been demonstrated that strain40 with different concentrations of fermentation filtrates had the inhibition to FOC4 mycelium and spores, mycelial colony diameter decreases,spores was inhibited from no inhibition to moderate, and severe inhibition. This shows that the fermentation broth of strain S40 had the inhibition to pathogen hyphae and spores.It could be seen from the effect of Antagonists S40 on bags seedlings of banana tissue culture,the disease index of treatment 3,4,5 (treatment3 represent:pathogen spore liquid added firstly and antagnistic bacterium added after an 24 hours;treatment4 represent:antagnistic bacterium added with pathogen spore liquid; treatment5 represent:antagnistic bacterium added firstly and pathogen spore liquid added after an 24 hours)were 23.75%,13.75% and 6.25% respectively,while the relative defence effect of above treatments were 71.2%,83.3%and 92.4% significantly preventing from banana wilt disease.In addition,there were difference among relative defence effect of three treatments,defence effect about the selection of inoculating antagonist was superior to that of simultaneous inoculation,defence effect with simultaneous inoculation was superior to that of inoculating pathogen firstly.Potted seedlings test showed that disease index about banana seedlings treated by antagonistic bacteria was significantly lower than those of untreated banana seedlings,it could be seen from the experiment that relative defence effect of treatment 3,4,5 were 60.12%、46.80% and 66.74% respectively in the 15 day, measured every 10 days those relative defence effect were 37.93%、48.27% and 48.27% in the 45 day,which was lower than the former.PPO, POD activity in the plants inoculated with the antagonistic bacteria has nearly doubled compared with the control,indicating that antagonists can induce plant production of defence enzyme. It had been obtained 400μg/ml rifampicin resistance after antagonist S40 being induced. the colonization experiments of the marked strain in the rhizosphere soil of banana plants showed that the number of antagonistic strains declined consistently with the extension of time,the number of antagonistic strains was only slightly more than the control in the 20 day or so.
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