Screening For Bacteria With Growth-promoting And Disease Control Effect To Processing Tomato In Drip Irrigation And Study On The Relevant Mechanism

The antagonist bacteria were selected in order to control main diseases of processing tomato from special soil entironment under drip irrigation mode in Xinjiang. The total 1029 isolates were obtained from 164 rhizosphere soil samples collected from drip irrigation field of main production areas of processing tomato in Xinjiang. The 456 antagonistic bacterium strains that resistant to Rhizoctonia solani were obtained in vitro antagonistic examination. 54 among 456 strains showed inhibitory activities against the seven pathogens including Pythium aphanidermatum, Rhizoctonia solani, Phytophthora capsici, Fusarium oxysporum f.sp.niveum, Alternaria solani, Sclerotinia sclerotiorum and Xanthomonas vesicatoria. The 12 strongly antagonistic bacteria were obtained by second round screening. They were identified as Bacillus sp. by gram dyeing and the bud spore dyeing. According to the growth characterization and antagonistic experiment, the 12 strains were mixed into 116 combinations. In vitro antagonistic examination, 23 mixtures having suppressive effect superior to mono antagonistic strains were obtained.By germination test and irrigation tomato seedlings with 54 mono antagonistic bacterium and 23 combinations, it was found that the sprouts and seedlings growth of processing tomato could be promoted significantly when treated with 6 bacterium and 6 mixtures. In the experiment of disease resistance to Rhizoctonia solani Kuhn, 17 bacterium and 12 mixtures displayed disease-resistant function in tomato seedling stage. Effect of growth- promoting and disease control effect of mono antagonistic bacterium SL-23, SL-35 and SL-44 and the combinations CL-7, CL-8, CL-10 and CL-20 were all remarkable. The second disease-resistant experiments and under field conditions confirmed the first one very well.12 combinations with disease-resistant activity were cultivated continuously for 20 generations. 8 stable combinations were obtained. The combinations CL-7 and CL-8 having remarkable growth-promoting and disease control effect were tested for the stability in the continuous cultivation process. pH value were measured after each generation. The suppressive effect of bacterium combination to the tomato damping-off were surveyed each 3 generations., and the bacterial quantity were also counted by dilution method.It was indicated that the pH value of 2 combinations were stable after cultured for 13~14 generations. The disease suppressive effects were invariable and the colony type and number of the combination were stable after cultivated for 12 generations.Mono antagonistic bacterium SL-23, SL-35 and SL-44 and the combinations CL-7, CL-8, CL-10 and CL-20 with remarkable growth-promoting and disease control effect were selected to determine the suppressive activity to the tomato damping-off under different temperature and pH value. It was indicated that temperature between 25-30℃and pH value 5~9 were best for these bacterium and combinations displaying obvious suppression activity to the tomato damping-off.When treated R.solani with fermentation liquid of SL-23, SL-44, CL-7 and CL-8, plasma concentration could be observed in this pathogen under the light microscope, and the electric conductivity and respiratory intensity of the pathogen primarily ascended and then declined. In tomato, the activity of resistant enzyme (SOD, POD, PPO, PAL) increased after treated...