| Summary: | 碩士 === 國立嘉義大學 === 生化科技學系研究所 === 99 === Trichoderma spp. are among the most common saprophytic fungi with high antagonistic activities against for a number of pathogens. The main biocontrol mechanisms that Trichoderma against pathogens are antibiotic and cell wall degrade enzyme production, mycoparasitism, nutrient competition, and induced resistance. In a previous study, T. virens FT-333 culture filtrate effectively protected tomato seedling from Phytophthora blight caused by P. capsici. In addition, the protein and peptide purified from FT-333 culture filtrate were found to have antibiotic properties. To further investigate the mechanism of induced resistance in tomato to against Phytophthora blight by T. virens FT-333 culture filtrate. The growth inhibition values (55.9%) of P. capsici were obtained at 3 days after pretreatment with FT-333 culture filtrate. The zoospore germination rate showed complete inhibition treated with culture filtrate. In the greenhouse experiment, zoospore suspension of P. capsici was inoculated to the root area one day after FT-333 culture filtrate treatment. The disease incidence was 43% as pretreating FT-333 culture filtrate on root, as compare with control (93%). Five days after pretreating FT-333 culture filtrate on leaves, the disease incidence of Phytophthora blight was 60%, as compare with control (87%). The defense gene expressions of tomato were observed 24 hrs after FT-333 culture filtrate treatment to the roots. The expression of Chi3, Chi9, GluA, and PR-1a were found to be induced after 48 hrs, but OPR3, LoxD, AOS2 and Pin2 were not induced. After pretreating FT-333 culture filtrate on leaves, the induction of PR encoding genes (Chi3, Chi9, GluB, and PR-1a) were observes after 48 hrs. In contrast, the genes involved in JA biosynthesis, such as OPR3, LoxD and AOS2, and JA-inducible Pin2 were not affected. Analyses of enzymes activity in leaves revealed that treatment with FT-333 culture filtrate on root increased chitinase and β-1,3-glucanase activities at 48 hrs. This work showed that the activation of SAR on tomato could be the major mode of action of T. virens FT-333 culture filtrate mediated disease resistance.
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