| Solanaceous scrop wilt caused by Ralstonia solanacearum E.F.Smith is a devastating disease. The pathogen has hundreds of hosts, strong tolerance and ineradicable habits. No appropriate disease-resistant cultivar and chemical pesticide with low toxicity and high efficacy were used commonly. PGPR (plant growth-promoting rhizobacteria) widely exists in plant rhizosphere soil. They can effectively prevent the occurrence of disease through different ways and promote plant growth. Therefore it is proposed to use PGPR to control bacterial wilt. Biocontrol method with environment-friendly feature becomes the hotspot of research.Bacillus cereus strain AR156, explored together by Xinyi Zhongkai Agricultural Chemical Industry Co., Ltd. and Nanjing Agricultural University, is one kind of biopesticide. To elucidate the strain’s mechanism of promoting growth and defending disease, biocontrol efficacy of AR156 on pepper wilt disease caused by Ralstonia solanacearum was investigated along with its growth promotion effects on pepper in the greenhouse, colonization ability, activation of the cellular defense responses such as hydrogen peroxide accumulation and callose deposition, and activation of pepper’s several enzymes. It was showed that biocontrol efficacy of AR156 on pepper wilt disease was up to 73.31%, meanwhile improving the fresh weight of pepper plants by 22.30%. It was found that strain AR156 could stably colonize in rhizosphere at 5×105 cfu per gram of root fresh weight on the 60th day after inoculation. Faster cellular defense responses were induced and the activity of plant defense-related enzymes including superoxide dismutase (SOD) and peroxidase (POD) were significantly enhanced in pepper treated with AR156 and R. solanacearum. In conclusion, the broad-spectrum resistance of AR156 to disease was realized by inducing cellular defense responses, activating several enzymes and producing vigorous colonies in pepper’s rhizosphere. In addition, the treatment of AR156 made the whole chlorophyll’s content in pepper leaves increase, which might be one reason why AR156 could promote pepper growth.Bacillus cereus strain AR156、Bacillus subtilis strain SM21 and Serratia marcescens strain XY21 were three potential biocontrol bacteria selected and stored by our laboratory. BBS family which included the three biocontrol bacteria and combinations was used in this study. We got two-strain combination and three-strain combination using the three biocontrol bacteria. In the following experiment, we studied BBS family including 3 single strain,3 two-strain combination and 1 three-strain combination prevented tomato wilt disease and promoted plant growth under greenhouse conditions. The result showed that mixture had better biocontrol efficacy and plant growth promotion effects than single strain. Three-strain combination and two-strain combination achieved better biocontrol efficiency and plant growth promotion effects than other treatments. The control efficiency were 84.31%and 74.20%respectively. The biomass increase were 44.03% and 32.58% respectively. In order to explore interaction relationship among the three strains, we studied on colonization dynamic state of BBS family in tomato rhizosphere soil. The result showed than three potential biocontrol bacteria could colonize well in the tomato rhizosphere no matter as single, both or three of them. The amount of Bacillus spp. strain AR156 and SM21 colonized in the tomato rhizosphere after treated 60 d was about 5×10 cfu per gram of root fresh weigh. The amount of Serratia spp. strain XY21 was about 5×106 cfu per gram of root fresh weigh. AR156 and SM21 of AR156+SM21 mixture exhibited better colonization ability than single strain. We inferred the reason was due to the interaction between AR156 and SM21. |
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