Effect And Mechanism Of Bacillus Subtilis On Crown Gall Pathogen In Pyrus Betulaefolia Bge. And Vitis

The plants of Pyrus betulaefolia Bge and Grape cultivar Kyoho that affected by crown gall pathogen were applied in this experiment. The pathogen of P. betulaefolia Bge crown gall was separated and the plasmid, biotype, and pathogenicity were identified. In the in vitro test of Bacillus subtilis against the pathogen of P. betulaefolia Bge and grape crown gall, the supernatant of Bacillus subtilis had inhibition to the growth of the Agrobacterium. The plant defensive enzyme activity of POD, PPO, PAL in the affected plants were analyzed and the mechanism of inhibition of Bacillus subtilis to the Agrobacterium was discussed. The effect of the Bacillus subtilis and the Agrobacterium on rooting of the grape cuttings was analyzed. That could be a way for the biocontrol to the pathogen. The main results were as following.1. The bacteria sampled from the crown gall that grew on the roots of the one year old P. betulaefolia plants were cultured and purified. Four bacterium strains similar to Agrobacterium were obtained. PCR assay showed that four strains had specific band and could be classified to the plasmid type of nopaline. Physiology and biochemistry identified the biotype was type Ⅱ.These strains caused crown gall after inoculated into the stems of the sunflower seedlings as index plants.2. 45 strains screened out of a total number of 100 B. subtilis had inhibition against vitis Agrobacterium through paper disc method, the diameter was between 3.3-20.0 mm. There was 9 B. subtilis strains which the inhibition diameter was above 11.0 mm.The supernate of 9161 B. subtilis strain had different inhibitory effect on 10 Agrobacterium strains preserved in our laboratory through double-plate method and oxford cup method, and it could completely inhibit the crown gall of Kyoho and P. Betulaefolia Bge, the efficiency of biocontrol was 100 %.3. The induction of POD, PPO, PAL activity was related to the plant resistance. The enzyme activity reached a peak in the third day of POD, PPO, PAL activity after inoculation the supernate of 9161 B. subtilis and pathogen, it was higher than the pathogen and sterile water treatment.4. The target band was tested in the inoculation site and above inoculation site after only inoculated pathogen, but there was no target band tested in all inoculation sites after inoculated B. subtilis and pathogen.5. The root number(11.7) after the supernate of 9161 B. subtilis treatment was higher than the pathogen(1.4), suspension(0.3) and sterile water treatment(5.4). The stem diameter, plant height, rooting rate and root length of suspension treatment was lower than sterile water.