| 1. Using the principle of homologous recombination and introducing lux gene of plasmid pRCG-Pps-Lux into the Ralstonia solanacearum CQPS by the natural fusion method, the exogenous luminescent enzyme labeled strain CQPS-Lux was obtained.. According to the result of the determined colony morphology, growth curve, pathogenicity and genetic stability of marked strain CQPS-Lux,, there were no significant differences between marked strain CQPS-Lux and original strain. And LuxCDABE gene of marked strain CQPS-Lux had better genetic stability. It showed that the marked strain CQPS-Lux could be used as an effective tool for the study of R. solanacearum.2. A systematic study was made on the colonization dynamics of marked strain CQPS-Lux in host plant tobacco and the distributed situation at different period. The results showed that the migration path of R. solanacearum infected tobacco was from root to stem base ministry, then to stem central and stem. The infection and colonization dynamics of R. solanacearum in tobacco were basically same in different tissues in vivo. The contents of R. solanacearum in tobacco plant tissues firstly increased slowly in a period and then quickly rose to a stable volume. Finally, it began to decline. In the different stages of disease, the bacteria content in tobacco roots organization was largest whereas in the upper stem tissue was minimal. The bacteria content in different parts of the tobacco stem tissue varied greatly. At the beginning the bacteria content in the lower part of stem, the middle of stem, and the upper part of stem in turn was from large to small. In the later period, the bacteria content in the central stem was more than the lower part of stem.3. The influence of three bactericides Streptomycin, Zhongshengmycin, thiodiazole copper to the colonization of R. solanacearum in tobacco, the motility, biofilm formation and the related gene expression of R. solanacearum were determined. The results showed that the three bactericides could decrease colonization amount of R. solanacearum to varying degree in tobacco after inoculated 1 d, 3 d, 5 d, expecially Streptomycin and Zhongshengmycin which greatly impacted the colonization. Compared with the untreated sample, the amount of R. solanacearum were reduced by 76.38%、97.66%、89.98% after treatment with Streptomycin for 1 d, 3 d, 5 d, respectively. The amount of R. solanacearum were reduced by 78.29%、98.33%、93.56% after treatment with Zhongshengmycin. However, Thiodiazole copper reduced the amount by 54.86%、36.15%、84.96%. All the three bactericides had significantly inhibiting effect on the biofilm formation of R. solanacearum, but the inhibition of Thiodiazole copper manifested obviously after treating 48 h. Moreover, they had significantly inhibiting effect on motility and seven gene expression of R. solanacearum, including motility related gene of Ralstonia solanacearum, MotA、MotB, Flagellar genes, FlhC、FlhD、FlgM, and Chemotaxis related genes, CheA、CheW.4. The effects of different applying methods of the three bactericides on tobacco to control the bacterial wilt were evaluated. The results showed that the three bactericides had different degrees of control effect on tobacco bacterial wilt disease with different application methods. The nest applying of Streptomycin, Zhongshengmycin had best control effects, which is stable and long duration on tobacco bacterial wilt and the control effect were up to 93.51%、45.94%、41.67% after transplanting for 7d、14d、22d. the control effect of Streptomycin was worse, which are 75.57%、37.12%、37.50% after transplanting for 7d、14d、22d, respectively. The control effects of root irrigation and dipping root of Streptomycin and nest applying of Thiodiazole copper were worst on tobacco bacterial wilt. And the treatment root irrigation of Thiodiazole copper had good control effect in the early stage of bacterial wilt disease. The control effect was reached to 72.25% after transplanting for 7d. |
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