| In the research, the impact of soybean and other plants to occurrence and damage degree of the clubroot disease in the following( cabbage and oilseed rape). The mechanisms of soybean as a bait crop to manage clubroot( Plasmodiophora brassica) was also studied. In addition, endophytic bacteria were isolated and identified from the galls of seedling and maturity oilseed rape, the control efficiency evaluation of some bacteria to manage clubroot. The results were as follows:1. The control efficiency evaluation of soybean as a bait crop to manage clubroot was studied. A field experiment of the crop rotation of rice, lettuce, potatoes, corn and soybeans with host plants( oilseed rape and cabbage) was conducted to control clubroot disease. Soybean had a good control efficacy( 92.10% and 80.28% on oilseed rape and Chinese cabbage, respectively). Greenhouse crop rotation experiment on soybean, peas and clover on the following cabbage clubroot control efficiency assessment showed that soybean managed clubroot in three experiments with the efficacy of 35.10% on the following cabbage. The dry weight and plant height of the following cabbage was significantly higher than the control and other treatments.2. The mechanism study of soybean as a bait crop to manage clubroot was conducted. One of the mechanisms was that soybean root exudates could stimulate resting spore germination. Non-host( soybean, peas and clover) and host( rape and Chinese cabbage) could significantly stimulate spore germination. The percentage of the germinated resting spores were in the treatments of the soybean root exudates( 40.13%), followed by spores incubated in the exudates from non-host plants( 26.97% in pea root exudates and 30.26% in clover root exudates), hosts( 26.80% in root exudates of oilseed rape and 28.68% in root exudates of Chinese cabbage), nutrient solution( 18.12%) or sdH2O( 14.48%). The effect of stimulating resting spore germination was obvious. The study also showed that N, Ca, B, Mg can inhibit resting spore germination from root exudates and soil.3. Clearly the influence of different rotations to P. brassicae in soil. Quantification of P. brassicae resting spores from inoculated potting mix by hemocytometer indicated that the P. brassicae resting spore concentration of the soil by treatment of soybean was 1.5×106 resting spores/g soil, that was significantly lower than oilseed rape( 4.2 × 106 resting spores/g soil), Chinese cabbage 6.6 × 106 resting spores/g soil), peas( 5.5 × 106 resting spores/g soil), clover( 3.7 × 106 resting spores/g soil), fallow( 9.3 × 106 resting spores/g soil). Quantification of P. brassicae resting spores from inoculated potting mix by qPCR indicated that that the P. brassicae resting spore concentration of the soil by treatment of soybean was 7.4 × 105 resting spores/g soil, that was significantly lower than oilseed rape( 2.5 × 106 resting spores/g soil), Chinese cabbage 2.3 × 106 resting spores/g soil), peas( 1.3 × 106 resting spores/g soil), clover( 1.2 × 106 resting spores/g soil), fallow( 2.5 × 106 resting spores/g soil).4. Endophytic bacteria were isolated and identified from the galls of seedling and maturity oilseed rape, the control efficiency evaluation of some bacteria to manage clubroot. Total 36 and 53 strains were isolated from the galls of seedling and maturity oilseed rape, all strains were identified and most species( 14.61% and 26.97%) belong to Bacillus and Pseudomonas. Firstly, use of Fusarium oxysporum as indicator fungus to plate screening that three strains has antibacterial effect, respectively Bacillus mojavensis, Bacillus amyloliquefaciens and Bacillus subtills. Secondly, the three strains all had some effect of inhibiting resting spore germination, 3 strains were 39.19%, 55.78% and 43.09% on inhibiting resting spore germination. Finally, the control efficiency evaluation of all three strains to manage clubroot of Chinese cabbage. Results indicate that 3 strains against clubroot in pot experiment were 19.15%, 46.26% and 30.29% on Chinese cabbage. |
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