Objectives Bacterial wilt caused by Ralstonia solanacearum is a widespread soil-borne disease, threatening the production of economic crops seriously. Biological control has been widely promoted as an efficient and environmentally friend method, however, the biocontrol efficacy is unstable owing to application methods, functional microbial strains, and etc. We investigated the general control effects of biocontrol agents as well as the primary influencing factors.
Methods In Web of Science and CNKI databases, literatures were searched using keywords “bacterial wilt disease” and “biocontrol agents”, “Ralstonia solanacearum” or “Pseudomonas solanacearum”, and “biological bacterium agent” or “biological bacterium control”. Then the literatures were screened with the following criterions: a no-biocontrol agent control, mean disease incidence, sample size, and a total of 113 pairs of data were obtained. Meta-analysis was used to assess the control effect and main influencing factors, the Random Effect Model in software Metawin was used to calculate the effect size (ES) between the treatment and control for comparing the efficacy of factors.
Results Application of biocontrol agents decreased the disease incidence of bacterial wilt from 77.35% to 37.13%, with an approximate control efficiency of 52%. The application mode, the ratios of functional microbial strains to Ralstonia solanacearum in soil, and the species of functional strains were found to be the main factors that influences the biocontrol efficacies. Soil application, root soaking, foliar spray, and seed treatment all showed significant control effect (CE), with the CE values of −0.80–−0.61, −1.34–−1.15, −0.96–−0.79, and −0.67–−0.49, root soaking performed the best with control efficiency as high as 66.72%. After the application of biocontrol agents, significant control efficiencies were received when the ratios of functional microorganisms to Ralstonia solanacearum in soil reached 1∶1, 10∶1, and 100∶1, with the most significant effect (63.62%) at ratio of 100∶1. Among the functional microbial strains types, Streptomyces showed better control efficiency than Pseudomonas and Bacillus, with a biocontrol efficiency of 74.08%.
Conclusions Application of biological agents has significant effects on the suppression of bacterial wilt disease incidence. For high and stable control efficiency, using root soaking method before transplanting, selecting Streptomyces genus as the functional microbial strains, and applying biological agents at rate of forming a ratio of functional microbial strain to Ralstonia solanacearum in 100∶1 were recommended.
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