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Occurrence of Fusarium Wilt and Other Diseases of Basil in Taiwan
本論文的目的，在調查與鑑定台灣羅勒發生的兩個新病害與描述一個未確定病害。2003年夏，台中大里地區羅勒於田間發生一萎凋型不明病害，罹病植株初期呈現矮化及落葉，接著嫩芽及莖頂出現壞疽。壞疽沿莖頂向下發展至全株，根部及莖部也會出現腐敗，罹病莖部表面偶有白色菌絲及孢子褥纏據；部分罹病植物呈半側萎凋；幼苗期受感染的植物會在短期內死亡，成株則可持續較長的時間。罹病株根莖維管束會有不連續褐化，尤其著生葉柄之莖部維管束褐化最為嚴重，呈黑褐色。從罹病組織可以分離得到一種Fusarium oxysporum Schlechtend，其菌落在PDA上呈白色並有橙紅色孢子褥以及藍或褐色菌核。孢子區分為三型。大孢子無色，鐮刀型，3到5隔膜，基部有足細胞，大小19.8-49.5×3.9-5.4μm；小孢子無色長橢圓形，單胞，大小5.9-16.3×2.4-4.9μm；厚膜孢子圓形或近圓形，壁厚，顏色較深，直徑7.4-12.3μm。病原性測試以剪根接種及混土接種接種於羅勒 (白骨羅勒) 幼苗上，可使其在溫室產生與田間相同病徵。將接種後之罹病株再分離，可分離得到與供試菌相同之病原菌，以此完成克霍氏法則 (Koch’s postulates )。供試菌株僅在唇形花科之羅勒 (白骨、紅骨) 造成感染，對同科及其他科的供試作物則無；又將採自羅勒不確定分化型之菌株與番茄、豌豆等六種不同分化型的F. oxysporum病原菌接種於羅勒，結果僅來自羅勒的病原菌可在羅勒上造成病徵，以此鑑定本病害是由Fusarium oxysporum f. sp. basilici (Dzidzariya) Armst. & Armst所引起，而正式稱該病害為羅勒萎凋病；病原菌於PDA上之菌絲生長溫度為8-36 ℃，但以24-28 ℃為最適；發病溫度在15 -35 ℃之間，且30-35 ℃時發病最嚴重；當接種源濃度在102 propagules/g soil或 102 spores/ml以上始發病；病原菌可經由孢子懸浮液於葉面接種而感染羅勒植株。另外，本研究也鑑定一種新的羅勒葉部病害，該病害會在初期於羅勒葉部邊緣形成黑色病斑，與健部有明顯界線，病斑隨後擴大，造成葉片畸形，嚴重時沿葉柄危害莖部；菌落在PDA上成白色，逐漸變為橄欖綠，而深黑色。分生孢子褐色，長橢圓形，鏈生於分生孢子柄頂，具2-5橫格及0-4縱格，大小為 21-56 × 7.2-16 μm，喙長2-6 μm ，經鑑定為Alternaria alternata (Fries : Fries) von Keissler，並將該病害定名為羅勒葉枯病。除此之外，一種不明原因的病害會在田間造成羅勒幼苗不分枝，莖部褐化水浸狀壞疽並且有根腐現象，在褐化部份出現白色菌絲纏聚或是著生黑色菌核，受感染植株會在兩週內死亡，其病徵類似羅勒菌核病。病原菌在28℃以下可以在PDA上產生菌核，菌絲生長溫度則以20℃為最適，發病溫度在24℃以下，其中在20℃為最嚴重。因本病原菌未在培養下觀察到其任何形式的孢子或菌核發芽行為，故先將其稱為羅勒疑似菌核病。
This study was aimed at determining and describing the Fusarium wilt and other diseases of basil in Taiwan. During 2003-2004, an undiagnosed wilt-type disease of basil was observed in central Taiwan. The first symptoms appeared as defoliation and stunting of the diseased plants, and then the buds and stems showed necrosis. Necrosis developed basipetally from the apex to the entire plant. Sometimes infected plants remained lateral wilt and stems and roots were rot. Vascular bundles showed discoloration. Infected seedlings died rapidly within a few days, and old plants might survive longer. Sometimes white mycelia and spore masses covered rotted stems and buds. A kind of fungus was consistently isolated from diseased tissue. The fungus produced 3 kinds of asexual spores. Microconidia produced abundantly from monophialides on potato dextrose agar (PDA); single-celled, hyaline, elliptic, or ovoid; 5.9-16.3×2.4-4.9μm. Macroconidia were the type “ Fusarium” spores. They were hyaline; 1-4 septates; 19.8-49.5×3.9-5.4μm. Chlamydospores were spherical to ovoid, smooth-surfaced, intercalary or terminal; 7.4-12.3×7.4-12.3μm. The fungus was determined as Fusarium oxysporum Schlechtend:Fr. It was pathogenic to basil 'White stem' in greenhouse inoculation experiments and produced symptoms similar to those observed in the fields. Host range tests in greenhouse indicated that this fungus could not attack tested Labiatae or other family plants except some cultivars of basil. Moreover, six different forma specialis of F. oxysporum derived from other host plants showed no pathogenicity to basil. Therefore, the pathogen was indentifield as Fusarium oxysporum f. sp. basilici (Dzidzariya) Armst. & Armst. and this disease was be named Fusarium wilt and crown rot of basil. Tested basil ‘White stem' also appeared symptoms by using suspension inoculation spraying method. The optimal temperature for the mycelial growth was at 28℃. Inoculation tests revealed that the optimal infection temperature for this disease were between 25-30℃. Another undiagnosed disease with leaf blight symptoms also occurred in basil fields during 2003-2004. The symptoms appeared black spot first on leaf margin, then leaf deformed. Finally, the symptoms extended from leaf to stem and plants showed leaf and stem blight. Conidia of the pathogen were brown, ellipsoidal, 21-56 × 7.2-16μm in size, short-beaked (2-6μm), with 2-5 transverse septa and 0-4 longitudinal septa, and catenulated at the apex of the conidiophores. The pathogen was identified as Alternaria alternata (Fries: Fries) von Keissler. Both of the optimal temperature for the mycelial growth and conidia germination were at 24℃. A stem rot of basil was also observed in fields. The infected plants appeared stem and root rot and they didn't branch. Sometimes white mycelia covered stem and sclerotia were produced on diseased leaf or stem tissue of basil. The symptoms seemed to be the same with Sclerotinia rot of basil. However, the sclerotia never apothecium germinated on artifical medium in laboratory. The optimal temperature for the mycelial growth was at 20℃. Sclerotia could be produced on PDA at or below 28℃, and the pathogen could infected the basil ‘White stem' at 16-24℃.
|Appears in Collections:||植物病理學系|
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