| Summary: | 碩士 === 國立中興大學 === 國際農學碩士學位學程 === 107 === Sweet peppers are one of the important vegetables crops worldwide including Indonesia. The large amount of peppers in Indonesia are grown for export market. Phytophthora capsici is an important disease which represents a serious threat to peppers production worldwide. The objectives of my study were to develop a Bacillus-based biocontrol agent to control Phytophthora root rot disease and to evaluate their ability to promote plant growth in sweet pepper. Bacillus subtilis strain WMA1 produced certain hydrolytic enzymes such as cellulase, protease, amylase, and lecithinase, and antibiotic compounds which resulting in inhibition of several phytopathogens including Rhizoctonia solani AG4, Fusarium solani PF7, and Phytophthora capsici. Under greenhouse condition this strain can reduced disease severity by 40 to 50 percent in infested soil containing 104 CFU per g of P. capsici compared to the water and SYB medium controls. Moreover, pepper seedlings treated with this strain displayed significantly higher shoot fresh mass, shoot dry mass, root fresh mass, root dry mass, number of leaves and plant height of peppers when compared to the control treatments. The B. subtilis WMA1 was tested positive for 2,3-butanediol, suggesting it may contribute to promote plant growth and stimulate plant defenses. The strain was also tested positive for Indole-3-acetic acid, an important phytohormones which can increase the root size, weight, and branching number thus allows the plant to uptake better nutrients. As for mineral solubilization, B. sublitis strain WMA1 showed positive result for phosphate solubilization. The strain also tested positive for biofilm formation and root colonization on sweet pepper roots. Results indicate that B. subtilis strain WMA1 provide promising biocontrol efficacy on Phytophthora root rot as well as plant growth promoting activity on sweet pepper.
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