| Summary: | 碩士 === 國立中興大學 === 園藝學系所 === 94 === The objectives of this study were to evaluate the effects of thermotherapy and chemotherapy on Shallot latent virus-elimination in green onion (Allium fistulosm L.). The shoot tips with three leaf sheathes were dissected from Shallot latent virus-infected (SLV- infected) two green onion cultivars ‘Lan Yang No.1’ and ‘Tao Yuan No.3’. Subsequently, the regeneration of virus-free plantlets was also tested for the production of healthy seedlings in vitro.
Results of thermotherapy revealed a 50 % reduction in virus-infected plants after being treated at 35℃ for 3-4 days. The percentage of virus free plantlets increased as temperature increased and treatment duration prolonged. The best result of 80-100 % virus elimination was obtained at 38℃ with treatment duration of 7 days.
In addition, when temperature rose, starch content in plantlets was increased. But there were adverse effects on plant height, chlorophyll and solubility sugar contents. Total soluble protein contents was the highest in thermotherapy at 38℃. The praline content in ‘Lan Yang No.1’ and ‘Tao Yuan No.3’ treated at 40℃ were 2 and 2.36 times higher than that of control, respeatively.
Results of chemotherapy revealed that SLV was eliminated completely by the medium with 25 mg/l of Ribavirin and cultivated for 2 weeks. However, there were adverse effects on fresh weight, height, number of leaf and chlorophyll content of explant as the chemical concentration and cultural period increased. The chemotherapy effect of Dithiouracil was not satisfied at any concentration, although it showed beneficial effect on plant height, fresh weight, leaf number and chlorophyll contents.
Results of explant proliferation showed that the plantlets cultured in MS medium containing 5 mg/l TDZ or 1 mg/l NAA and 2 mg/l BA could be promoted for shoot regeneration significantly. MS-free and MS medium with 5 mg/l 2ip or 5 mg/l Kinetin could promote the root induction of green onions.
It is suggested that the green onion materials can be treated at 38℃ for one week or cultured in medium containing 25 mg/l Ribavirin for two week to eliminate SLV-virus. After the thermotherapy or chemotherapy, the plantlets are transfer to MS medium containing 1 mg/l NAA and 2 mg/l BA for proliferation. After one month, the plantlet are further transferred to plant grow regulator-free MS medium for another one month for rooting. After acclimatization, the SLV-free health seedling cam be derived.
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