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|標題:||自水蘊草Hydrilla verticillata分離之葉芽線蟲Aphelenchoides sp.之鑑定與生態研究
The classification and ecology of Aphelenchoides sp. isolated from Hydrilla verticillata
Yang, Tsung Hsun
|關鍵字:||葉芽線蟲;線蟲鑑定;型態發生學;水蘊草;Aphelenchoides sp.;Hydrilla verticillata;identification of nematodes;phylogenetic analysis||出版社:||植物病理學系||摘要:||
自水蘊草Hydrilla verticillata分離之未知種葉芽線蟲Aphelenchoides sp.可寄生於水蘊草、金魚藻Ceratophyllum demersum與不同種菊花草Cabomba spp.等水生植物之頂芽與葉腋。此葉芽線蟲兩性皆為蠕蟲狀，雌蟲體細長，長度為0.69-0.97 mm，尾端為多疣突狀之尾突。口針長10 μm、口針基部有膨大構造；蟲體中段側帶寬度約占體寬之0.18倍，具有四條側線。雌蟲單卵巢，卵母細胞呈單列且後部子宮支發達，向後端延伸長度大於50%陰門至肛門長度。雄蟲精巢單列且尾部具交接刺。依據de Man’s 測量項目測得Aphelenchoides sp.之型態測量值，經比較40種已發表之葉芽線蟲，發現與A. fragariae之測量值無差異，而兩者之差異為側線數目。其餘種類經比較並無相符。Aphelenchoides sp.對水蘊草莖及頂芽組織具有趨化性，進一步以棉藍染色可發現侵入莖組織之現象。經由接種不同種類水生植物發現可自接種後20日之水蘊草、黃金錢草Lysimachia nummularia、南極杉Hydrotriche sp.及矮珍珠草Glossostigma clatinoides 上分離得Aphelenchoides sp.，但植物無病徵顯現且經棉藍染色確認無內寄生現象。Botrytis cinerae及Alternaria citri皆可供Aphelenchoides sp.族群繁衍，以B. cinerae作為其食物來源時線蟲族群繁殖數量為最大。本研究使用rDNA作為鑑定分類之輔助工具，經比較Aphelenchoides sp.與A. fragariae rDNA，兩者於5.8S rDNA、ITS1及ITS2三序列之相似度分別為100%、96%及95%。而使用Aphelenchoides sp.與其他種類線蟲之rDNA進行比對分析，發現不同區間之相似度過低。故由本論文對Aphelenchoides sp.之形態學及生態學研究推論此未知種葉芽線蟲為一寄生於水生植物之外部寄生性線蟲，且可能為一未發表之新種。
An unknown Aphelenchoides sp. was isolated from aquatic plants in a nursery in Taichung, Taiwan. Nematodes were observed to accumulate in the buds of Ceratophyllum demersum, Cabomba spp., and also in the axillar part of Hydrilla verticillata. This Aphelenchoides population had a body length ranging from 0.69-0.97 mm, with slender body shape tapering to a multi-papillate tail tip. The stylet averaged 10 μm with slight basal swelling. The lateral field was approximately 0.18 times body width with four incisures. Females had a single row of oocytes and an well developing postuterine sac extending more than 50% the distance of valve to anus. Males were characterized by the rosethorne-shaped spicules. The morphometrical measurements were very similar to A. fragariae but differed in the number of incisures. Comparing morphometrics and morphology with 40 described Aphelenchoides species found no congruent species. Chemotaxis tests indicated that this nematode could be attracted by the apex and stem tissue sections of Hydrilla verticillata and was later found inside the tissue by staining. Aphelenchoides sp. could be reisolated from Hydrilla verticillata, Lysimachia nummularia , Glossostigma clatinoides, and Hydrotriche sp. after inoculating for 20 days. The plants inoculated with Aphelenchoides sp. showed no disease symptoms nor the phenomenon of endo-parasitic. Among five fungus species tested as the food source, Botrytis cinerae could sustain the largest population of nematodes. The rDNA sequences was obtained for identification and phylogenetic analysis of Aphelenchoides sp. Comparing Aphelenchoides sp. and A. fragariae showed 96% and 95% similarity in ITS1 and ITS2 region respectively, and 100% identical in 5.8S rDNA sequences. The phylogenetic analysis resulted unreliable relationships between Aphelenchoides sp. and other nematodes by using the rDNA sequences. The data suggested Aphelenchoides sp. was potentially an ecto-parasitic nematode according to the observation and the ecological study. Work is underway to describe this population of Aphelenchoides found on aquatic plants in Taiwan as a new species.
|Appears in Collections:||植物病理學系|
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