| Summary: | 碩士 === 國立中興大學 === 植物病理學系 === 87 === Symptoms of stunting in growth and mild mosaic and distortion on leaves were noticed on freesia plants growth in Mei-fon. Inoculation with crude extracts from diseased plants failed to produce symptom on indicator plants. Leaf extracts from diseased plants were analyzed by differential centrifugation followed with gel filtration and three absorption peaks were observed at wavelength 254nm. The preparation from the first absorption peak induced yellow local lesions on the leaves of Chenopodium quinoa. Electron microscopic examination of the preparation revealed the presence of filamentous virus particles of 750 ×12nm. On the other hand, virus particles were not seen in the samples of the second and the third absorption peaks. The filamentous virus also induced local lesions on C. amaranticolor and vague chlorotic lesions on C. murale after mechanical inoculation. The virus had a thermal inactivation point between 50 and 60℃, a dilution end point of 10-3~10-4 and the longevity in vitro about 7 to 9 days at room temperature. Electron microscopic analysis of ultrathin section of inoculated leaves revealed the accumulation of scrolls and laminated aggregates in the cytoplasm. The above results indicated that the virus isolate is a member of potyvirus. Based on information on particle morphology, host reactions, and physical properties the virus isolate was tentatively designated as Vallota mosaic virus (ValMV). Antisera were produced against purified virus for detection. A large proportion of plant protein was removed when extracts were treated with sixth volume of a mixture of carbon tetrachloride and n-butanol (2:1). An antiserum was produce from a New Zealand white rabbit immunized with the purified virus particles. Immunoglobulin G (IgG) were purified from the antiserum by precipitation in 12% sodium sulfate. Horseradish peroxidase (HRP) was used to prepare enzyme-antibody conjugate. Tests of antibody -HRP conjugate showed false positive results in DAS-ELISA. Thus, the antiserum was cross-absorpted with healthy-plant sap to remove non-pathogen-specific antibodies. Healthy—plant sap was processed and supernatant fluid after centrifugation was collected for cross-absorption. After non-pathogen—specific materials were removed, the IgG was used to prepare HRP-antibody conjugate. This HRP-conjugate in DAS-ELISA test using coating non-absorption IgG shows no background reaction in negative controls. Test of field freesia samples by using the HRP-conjugate showed that plants showing mild mosaic and narrowing on leaves were positive in DAS-ELISA
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