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Plant gray mold disease caused by necrotrophic pathogen Botrytis cinerea , has been a serious threat to many important crops. It is urgent and necessary to seek an effective and environmentally friendly control strategy to control grey mold disease during the crop production. Moreover, it is also urgently needed to clear understand how the strategy works. To screening an efficient biocontrol agent in control of gray mold disease caused by B. cinerea , one hundred strains, which have the potential in controlling plant diseases, were selected from our laboratory’s strain library, and employed to our research. The results in the study indicated that Bacillus velezensis could act as a potential and efficient biocontrol agent (BCA), and two B. velezensis strains 5YN8 and DSN012 were screened out with high antagonistic and hydrolase activity, which could significantly control pepper gray mold disease and promote the pepper growth. Further deeply study on biocontrol mechanism indicated that B. velezensis could suppress the growth and spore formation of B. cinerea by secreting some secondary metabolites or releasing numbers of volatile organic compounds (VOCs). In the other hand, we also found that B. velezensis could trigger plant basal immunity. The BCA could increase the expression of SA signal markers and plant defense related genes. It was able to induce hydrogen peroxide accumulation and plant related enzyme activities in leaves of pepper as well. This study provides another high-efficiency, and potential strategies for the biological control of gray mold disease. It is the first report of B. velezensis strain which can control gray mold disease, In addition, it is also the first to comprehensively illustrate how the strains can efficiently protect pepper from B. cinerea attacking. [ABSTRACT FROM AUTHOR]

Rice sheath blight caused by Rhizoctonia solani Kühnis increasingly threatening rice production in China. DNA fingerprints of 220 R. solani strains isolated in 11 provinces of China were established by random amplified polymorphic DNA (RAPD)-PCR. Cluster analysis of strains isolated from the same region showed high similarity, indicating that the genetic diversity of R. solani strains is significantly related to geographical origin. We assessed potential bio-control abilities of bio-control agents (BCAs) by values according to inhibition zones against R. solani , extracellular hydrolytic enzymes activity and siderophores production in vitro. Fourteen strains with diverse expected bio-control potential were tested for their bio-control efficacy against rice sheath blight caused by 11 pathogenic exemplars and for growth promoting ability, separately. Bio-control efficacy of single bacterium against various R. solani strains differed significantly (−36.23% ∼ 88.24%), while Pseudomonas fluorescens 4aYN11 achieved a relatively stable control efficacy of 32.26%–78.79% and growth promotion of 18.43%. Pearson correlation coefficient between bio-control efficacy of each BCAs and their assessment is 0.717. In the present study, we established an improved strategy for screening stable bio-control agents based on an assessment system, their growth promotion potential and phylogenetic diversity of pathogen R. solani , and the result provides us not only one promising bio-control strain 4aYN11 with an average bio-control efficacy of 56.50%, but also a practical way for future screen of novel BCAs. [ABSTRACT FROM AUTHOR]

PSX is a combination of biocontrol bacteria that can potentially prevent and control soil-borne diseases for a variety of crop cultivars. In this study, we investigated the utility of PSX in controlling root-knot nematodes in tomato under field conditions. The application of PSX reduced the severity of disease caused fromMeloidogyne incognitaby 63–69% and increased tomato yield by 31.5–39%. Furthermore, to investigate the effect of PSX treatment on tomato fruit quality, we quantified the soluble sugar, titratable acid, soluble solids, and vitamin C contents in fruit postharvest. We demonstrated that PSX treatment improved tomato fruit quality. Finally, we also showed that the total nitrogen (N), available N, potassium, and organic matter contents in the soil increased after PSX treatment. PSX is a promising biocontrol preparation that can provide beneficial effects to tomato growers, including biological control of root-knot disease, plant growth promotion, enhanced tomato fruit quality, and increased levels of organic fertilisers in the soil. [ABSTRACT FROM PUBLISHER]