| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 107 === Colletotrichum spp. are pathogens of anthracnose diseases of many agricultural crops. Colletotrichum spp. produce a highly specialized penetration structure called appressorium. Appressorium has a semipermeable melaninized layer that provides resistant to physical and chemical stresses, and allows building enormous turgor pressure for directly penetration into host epidermal cells through cuticle. It also serves as a dormant and survival structure during latent infection. To date, many control agents were developed based on their inhibition ability of spore germination, mycelial growth or appressorium formation of Colletotrichum. However, there were few researches focusing on targeting appressorium penetration. In this study, we evaluated the ability of various plant protection agents and environmental stresses on reduction of appressorium penetration. A platform that allowed assessing the penetration ability of appressorium was established with onion epidermis. Colletotrichum species of mango anthracnose pathogen (Colletotrichum asianum TYC-2) and crucifer anthracnose pathogen (Colletotrichum higginsianum CH063A) were used in assays. On the beginning, the platform was used to screen fungicides that are able to suppress appressorium penetration. Nine out of 27 labelled fungicides for mango production efficiently suppressed appressorium penetration of two anthracnose pathogens more than 90% while fluazinam, myclobutanil, oxine-copper and mancozeb only suppressed the penetration of C. asianum TYC-2. When the green fluorescent protein (Histone H1::GFP) expressing strains was applied to determine appressorium survival rates after fungicide treatments, treatments with pyraclostrobin, tebuconazole and metconazole displayed the lowest survival rates followed by treatments with fluazinam, difenoconazole and prochloraz. In addition, thyme and cinnamon essential oils effectively inhibited the penetration of C. asianum TYC-2 appressorium more than 90%, and reduced the survival rate below 15%. Three microorganisms inhibited appressorium penetration of two anthracnose pathogens more than 80%. A treatment with irradiation UV light (UVC) exposure for 30 minutes completely inhibiteed C. asianum TYC-2 appressorium penetration, but only reduced C. higginsianum CH063A penetration rate to 39%. Under different pH conditions, the penetration of appressorium was only highly affected at pH 2 and pH 12. Hot water treatment (45℃ for 20 min or 50℃ for 3 min) reduced the penetration of the appressorium as well. In the control assays of mango fruits and leaf with conidia inoculation, treatments with thyme essential oil, Bacillus subtilis X2, Bacillus velezensis S2 and Bacillus amyloliquefaciens B2 effectively reduced the anthracnose lesions on the mango fruits with inhibition rate of 61%, 67%, 57% and 54%, respectively. However, anthracnose lesions of mango leaf and fruits did not reduce by exposing to irradiating UV light. The combination treatment of thyme eassential oil and hot water, hot water and fungicides, thyme essential oil and X2 effectively reduced lesion sizes on mango fruits. In the future, we will use the platform to evaluate more prevention methods, and integrated them to achieve the purpose of integrated pest management.
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