| Summary: | 碩士 === 臺灣大學 === 園藝學研究所 === 96 === Cymbidium mosaic virus and Odontoglossum ringspot virus are the most prevalent infecting orchids worldwide. Phalaenopsis and Doritaenopsis spp. are important export orchids in Taiwan. The viruses would reduce plant vigor and lower flower quality, thus affects economic value. The objectives of this study were trying to increase Cymbidium mosaic virus（CymMV）resistance of both Phalaenopsis and Doritaenopsis spp. CymMV proper inoculation concentration for all cultivars were determined, and to investigate the effects of chemical treatment and orchid mycorrhiza on CymMV resistance. The inoculation of CymMV RNA was used to determine proper inoculation concentration for each cultivar. Three cultivars of virus free orchids which were pre-detected by RT-PCR method including KC1935（Phalaenopsis Taisuco Kaaladian × Phalaenopsis Grace Palm）, KC1943（Phalaenopsis Taihort Snowdian ‘Minho’× Phalaenopsis Yukimai Dream Morida）and KC3925（Doritaenopsis Minho Princess）. After the inoculation of five concentrations（0.01、0.1、0.5、1 and 2 μg/μl）of CymMV RNA for one mouth, CymMV proper inoculation concentration were detected by RT-PCR. Results showed that the CymMV proper inoculation concentration of KC1935 and KC3925 were 0.5 μg/μl, but for KC1943 was 0.1 μg/μl. Effects of chemical treatments and orchid mycorrhiza on CymMV resistance were investigated. The study including three parts, i.e. the orchid plants were inoculated with one species of Rhizoctoria spp. fungi（R01, R02, R04, R15 and R19）or spraying with different concentrations of chitosan or salicylic acid. After two months, CymMV proper inoculation concentration（0.5 or 0.1 μg/μl）were inoculated to the leaves of three orchid cultivars, then examined virus infection by RT-PCR for another one month. Results showed that either inoculated the orchid plants with R04, then spray with salicylic acid 1 mM per month or biweekly spraying with chitosan 2 ml/L or salicylic acid 1 mM or 2 mM, could very effectively increase the orchid plants to resist CymMV and keep the plant in virus-free state. Results also showed that the resistance of orchid plants to CymMV varied with orchid cultivars. It was suggested that each orchid cultivar might show different response for salicylic acid, chitosan or orchid mycorrhizal fungi, thus for new cultivar, the OMFs, chemical treatment concentrations and intervals should be tested in advance.
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