Chen-Hsuan Tsai

When a plant is infected by a pathogen, endogenous immune responses are initiated. When the initiation of these defense responses is induced by a pathogen-associated molecular pattern (PAMP) of a pathogen, it is called PAMP-triggered immunity (PTI). Previous studies have shown that Bacillus amyloliquefaciens PMB05 can enhance PTI signals and improve disease control of bacterial soft rot and wilt in Arabidopsis thaliana. In the context of controlling bacterial wilt disease, the involvement of a mitogen-activated protein kinase (MAPK) signaling pathway has been established. Nevertheless, it remains unclear whether this pathway is also required for B. amyloliquefaciens PMB05 in controlling bacterial soft rot. In this study, A. thaliana ecotype Columbia (Col-0) and its mutants on a MAPK pathway-related pathway were used as a model and established that the ability of B. amyloliquefaciens PMB05 to control soft rot requires the participation of the MAPK pathway. Moreover, the enhancement of disease resistance by PMB05 is highly correlated with the activation of reactive oxygen species generation and stomata closure, rather than callose deposition. The spray inoculation method was used to illustrate that PMB05 can enhance stomatal closure, thereby restricting invasion by the soft rot bacterium. This control mechanism has also been demonstrated to require the activation of the MAPK pathway. This study demonstrates that B. amyloliquefaciens PMB05 can accelerate stomata closure via the activation of the MAPK pathway during PTI, thereby reducing pathogen invasion and achieving disease resistance against bacterial soft rot.

Sweet pepper is an important vegetable in the world. Bacterial leaf spot, caused by the pathogen Xanthomonas perforans, is a limiting factor that significantly reduces the quality and yield of sweet peppers. The use of chemical fungicides is currently the main disease-control method for bacterial leaf spot disease. It is important to develop an eco-friendly biocontrol method by using antagonistic microorganisms. Bacillus amyloliquefaciens PMB04 has strong antagonistic effects against pathogens and can inhibit the occurrence of diseases. B. amyloliquefaciens PMB04 has the potential for the development of a disease-control product. Primarily, PMB04 contained a strong inhibitory effect against all isolated X. perforans strains. In the inoculation assay, the severity of bacterial leaf spot disease on sweet peppers was reduced by PMB04 bacterial suspensions. To increase the convenience of field applications in future prospects, the development of the PMB04 fermentation liquid was carried out using different ratios of brown sugar and yeast extract in a 30 L fermentation tank. The results exhibited that the fermentation liquid of the 3-1 and 2-1 formulas obtained the highest bacterial population in a 30 L fermentation tank. The fermentation liquid of the 0.5-0.5 formula was the most stable formula for two different conditions in terms of a consistent bacterial population and sporulation. In addition, the 200-fold dilution of the 3-1 and 0.5-0.5 fermentation liquids revealed the best control efficacy on bacterial leaf spot disease of sweet peppers. Additionally, the results of the 0.5-0.5 fermentation liquid (PMB4FL) with different dilution concentrations also demonstrated that the 200- and 500-fold dilutions had the best control efficacy. To understand the effect of commonly used copper-containing fungicides on sweet peppers on the application of microbial agent PMB4FL, the effects of copper hydroxide and tribasic copper sulfate on the growth of X. perforans strains and B. amyloliquefaciens PMB04 were assayed. The results exhibited that the above two fungicides did not have any inhibitory effect on the growth of PMB04 but had a strong inhibitory effect on the X. perforans strain. In the follow-up control experiment, the treatment of copper hydroxide had no synergistic effect with PMB4FL to control bacterial leaf spot disease. We concluded that the use of the PMB4FL fermentation liquid alone on the leaves could effectively control the occurrence of bacterial leaf spots in sweet pepper crops.

Sweet pepper is an important vegetable in the world. Bacterial leaf spot caused by the pathogen Xanthomonas perforans, is a limiting factor that significantly reduces the quality and yield of sweet pepper To control this disease, the use of chemical fungicides is currently the main disease control method. Thus, we want to develop an alternative method by using antagonistic microorganisms. Under this demand, Bacillus amyloliquefaciens PMB04 has strong antagonistic effects against pathogens and can inhibit the occurrence of diseases. B. amyloliquefaciens PMB04 has the potential for the development of a disease control product. Primarily, PMB04 revealed to contain a strong inhibitory effect against all isolated X. perforans strains. In the inoculation assay, the severity of bacterial spot disease on sweet peppers was reduced by PMB04 bacterial suspensions. To increase the convenience of field application for future prospects, the development of PMB04 fermentation liquid was carried out with different ratios of brown sugar and yeast extract in a 30-liter fermentation tank subsequently. Results exhibited that the fermentation liquid of 3-1 formula obtained the highest bacterial population in a 30-liter fermentation tank. The fermentation liquid of 0.5-0.5 formula was the most stable formula under two different conditions in terms of consistent bacterial population and sporulation. In addition, the 200-fold dilution of 3-1 and 0.5-0.5 fermentation liquids revealed best control efficacy on bacterial leaf spot of sweet pepper. Additionally, the results of the 0.5-0.5 fermentation liquid (PMB4FL) with different dilution concentrations also showed that the 200- and 500-fold dilutions had the best control efficacy. To understand the effect of commonly used copper-containing fungicides on sweet peppers on the application of microbial agent PMB4FL, the effects of copper hydroxide and tribasic copper sulfate on the growth of X. perforans strains and B. amyloliquefaciens PMB04 were assayed. The results exhibited that the above two fungicides did not have any inhibitory effect on the growth of PMB04, but had a strong inhibitory effect on the X. perforans strain. In the follow-up control experiment, the treatment of copper hydroxide had no synergistic effect with PMB4FL to control bacterial leaf spot. We concluded that the use of PMB4FL fermentation liquid alone on the leaves can effectively control the occurrence of bacterial leaf spot in sweet pepper crops.