西瓜銀斑病毒在西瓜上之發生生態

Ecology of Watermelon Silver Mottle Virus Disease on Watermelon in Taiwan

陳慶忠(C. C. Chen) ； 柯文華(W. F. Ko) ； 白桂芳(K. F. Pai) ； 葉錫東(S. D. Yeh)

《植物病理學會刊》 13卷4期 (2004/12) Pp. 317-328

https://doi.org/10.6649/PPB.200412_13(4).0010

摘要

西瓜銀斑病毒(Watermelon silver mottle virus，WSMoV)於1988年在台灣首次被鑑定，自此本病成爲西瓜栽培之一重要病毒病害。1991-1995年間於彰化縣大城鄉調查西瓜銀斑病毒病罹病度與南黃薊馬(Thrips palmi Karney)棲群密度，結果顯示夏、秋作高溫季節西瓜感染WSMoV較爲嚴重，而春作則較輕微。春作由於生育初期氣溫低及越冬後媒介昆蟲－南黃薊馬蟲口密度低以及病毒源少，西瓜受感染WSMoV的程度輕微。夏、秋作由於西瓜生育期間氣溫高、田間媒介昆蟲蟲源及病毒源均較豐富，以致發病較爲嚴重。夏、秋作西瓜罹病植株約於定植後3-4週開始顯現病徵，發病高峰期於隨後之二週出現，由於發病盛期正值西瓜欲留果（每期作每株只留一採收果）之開花或幼果期，以致罹病西瓜所結之瓜實生育受嚴重影響。以迴歸分析法分析開花前即定植後四週之總降雨量與全期作南黃薊馬總蟲口密度之相關，結果1991-1994年夏作二者呈顯著相關，但春、秋作則相關不顯著。分析每週蟲口密度與其後第三週西瓜WSMoV罹病率之相關，結果1993-1995年春作及1991-1994夏作二者均呈顯著相關；1991-1993秋作二者相關不顯著。WSMoV感染西瓜除引起黃化型病徵外，在田間尚有一種銀斑型病徵，二者在血清類緣關係、核酸層次、病毒形態及薊馬傳播特性比較並無差異。中部地區是常見感染WSMoV之瓜類作物除西瓜、冬瓜外，洋香瓜及胡瓜亦受到嚴重感染爲害；田間南瓜、絲瓜、扁蒲、越瓜等雖也能偵測到罹病株，但罹病率極低。調查11種野生植物（雜草）中野莧及龍葵證明爲WSMoV之寄主植物，其中龍葵亦爲南黃薊馬之寄主植物。在田間野莧及龍葵都見於西瓜生育後期或收穫後方始表現病徵，推測此類雜草在冬季非瓜類栽培期扮演著WSMoV病毒源保存及傳遞的部份角色。

關鍵字

西瓜 ； 西瓜銀斑病毒 ； 生態學 ； 寄主植物

並列摘要

Watermelon silver mottle virus (WSMoV) has become a devastating disease of watermelon in central Taiwan since it was firstly identified in 1988. The survey of the relatedness between disease incidence and population density of the viral vector-Thrips palmi Karny had been conducted during the crop seasons from 1991 to 1995. The collected data showed that the disease incidences were low during the spring season due to the low temperature, the low population density of T. palmi, and sparse source of WSMoV in the early stage of growing watermelons. On the contrary, the heavy incidences were observed during summer and autumn seasons due to increase in the temperature, vector population, and virus sources. In summer and autumn crop seasons, the symptoms of WSMoV emerged at 3 to 4 weeks after transplanting and progressed during the following weeks which were the flourishing and fruit-forming stages of the single target fruit of each transplant. Consequently, the watermelon plants and fruits were severely affected. Significant correlations can be observed between the total rainfall before flourishing (4 weeks after transplanting) and the total number of T. palmi during summer crops in 1991 to 1994, but not in spring and autumn crops. Correlations between the weekly population density of T. palmi and the disease incidence after every third week of each field survey of the vectors could also be observed in spring crops of 1993 to 1995 as well as in summer crops of 1991 to 1994, but not be observed in autumn crops of 1991 to 1993. Two types of symptoms, i.e. chlorotic mottle and silver mottle, have been observed in the field when watermelons were infected by WSMoV. However, the individual viral isolates obtained from watermelons showing different symptoms were indistinguishable in morphological, serological, molecular assays and thrip transmission. In addition to watermelon (Citrullus vulgaris) and wax gourd (Benincasa hispida), cucurbits, such as Cucumis melo and Cucumis sativas, were also seriously infected by WSMoV in the fields of central Taiwan. WSMoV could also be detected in Cucumis melo Conomon group, Cucurbita pepo cv. Field pumpkin, Luffa aegyptia and Lagenaria leucantha, however, with a relatively low rate. Weed plants, Solanum nigrum and Amaranthus viridis, have been confirmed as natural hosts of WSMoV with serological and electron microscopic approaches, while S. nigrum has also been proved experimentally to be a host of T. palmi. These weeds are possible alternative hosts of WSMoV and habitant of T. palmi in the field during the winter season when no other cucurbits were grown.

並列關鍵字

watermelon ； Watermelon silver mottle virus ； ecology ； host plants