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Identification of Fusarium wilt of Cucumber and Screening of Nonpathogenic Fusarium oxysporum for the Disease Control
Fusarium oxysporum f. sp. cucumerinum
nonpathogenic Fusarium oxysporum
|摘要:||本篇論文的目的即在鑑定胡瓜萎凋病的病原菌及建立其基本資料, 並篩選無病原性尖鐮孢菌菌株供生物防治之應用。胡瓜萎凋病在台灣各地胡瓜田區或僅零星發生, 或其發病率介於25%-75%。本病害可危害各生長期之胡瓜, 除造成幼苗猝倒及成株黃化萎凋、維管束褐化之外, 亦會引起胚軸與根部交接處(peg), 主根及少數支根腐爛。利用各種瓜類作物幼苗做交互接種試驗顯示源自胡瓜的Fusarium oxysporum菌株, 除了胡瓜之外, 亦會感染洋香瓜、香瓜和越瓜; 對西瓜、苦瓜和絲瓜則不具病原性。源自洋香瓜、西瓜、苦瓜和絲瓜的萎凋病菌僅感染其原寄主, 不感染胡瓜。故鑑定台灣產之胡瓜萎凋病菌為F. oxysporum .f. sp. cucumerinum Owen。市售胡瓜種子帶菌率極低(0.4%)。病原菌主要從胚軸基部和根部的交接處(peg)侵入, 亦可由支根侵入, 分別造成幼苗猝倒, 和成株萎凋的兩階段病徵。從交互保護接種試驗篩選173株無病原性尖鐮孢菌的結果, 獲得分離自花蓮土壤之Fo-366菌株具保護胡瓜初期生長, 延遲發病的效果。經土壤混菌法接種病原菌發現花蓮土壤為胡瓜萎凋病之抑病土, 保護胡瓜至生長後期, 其可能之抑病因子在本文中討論。無病原性尖鐮孢菌Fo-366 和病原菌Foc-100菌株在2%半乳糖取代蛋白凍之修正PCNB培養基上有不同呈色, 可加以辨識, 可在防病機制之研究應用。|
This study was aimed at determining the cause and some basic information of Fusarium wilt of cucumber and screening the nonpathogenic Fusarium oxysporum for its biological control. This disease did not occur in every cucumber field, but in some fields, their disease incidence had up to 25%-75% during the 1997-1998 survey. The disease cucumber was commonly in patches and showed not only damping-off of seedlings, vascular discoloration and wilt of adult plants, but characteristically showed rot symptoms on peg, primary root and several secondary roots. Based on completion of Kock's Postulates, and cross-inoculation tests on seedlings of cucumber and other cucubitaceous plants indicated that the Fusarium from cucumber was pathogenic on cucumber, melon, muskmelon, and oriental pickling melon, but not on watermelon, bitter gourd and loofah. Moreover, The wilt fusaria from muskmelon, watermelon, bitter gourd, and loofah were pathogenic on their original hosts, but not on cucumber. Therefore, the Fusarium from cucumber was identified as F. oxysporum f. sp. cucumerinum Owen. The isolation frequence of the pathogen from cucumber seeds (Vantage) obtained from market was 0.4%. The pathogen could penetrate cucumber plants from peg and secondary roots and causeing damping-off and wilt symptoms, respectively. In the cross-protection tests, among 173 isolates of nonpathogenic F. oxysporum, an isolate (Fo-366) obtained from Hualian soil could protect cucumber plants from F. oxysporum f. sp. cucumerinum for at least 42 days after challenge inoculation. Hualian soil was proved to be a suppressive soil to Fusarium wilt of cucumber by soil infestation inoculation method in greenhouse. The possible suppressive factors in Haulian soil were discussed. Colonies of isolates Fo-366 (nonpathogenic F. oxysporum) and Foc-100 (pathogen) produced different pigmentation and could be distingushed from each other easily when grown on a modified PCNB medium (using 2% galactose instead of 1.5% peptone).
|Appears in Collections:||植物病理學系|
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