小花蕙蘭細斑病菌Fusarium proliferatum之生長與寄主侵染特性

Characteristics of Growth and Infection of Fusarium proliferatum Causing Fleck Spot on Oriental Cymbidium Leaf in Taiwan

黃巧雯(Chiao-Wen Huang) ； 黃晉興(Jin-Hsing Huang) ； 謝廷芳(Ting-Fang Hsieh)

《台灣農業研究》 71卷1期 (2022/03) Pp. 35-47

https://doi.org/10.6156/JTAR.202203_71(1).0004

摘要

細斑病（fleck spot）為小花蕙蘭栽培過程中重要葉部病害之一，主要危害幼葉，在幼葉上產生細小黑褐色圓形或不規則形病斑，有時病斑周圍產生淡黃色暈環，雖然葉片被病原菌感染後其病斑不會繼續擴大，但葉片具有斑點不美觀而影響植株的商品價值，偶而會造成葉片基部腐敗而死亡。由病組織所分離到真菌，依據形態特徵及核醣體內轉錄區間與translation elongation factor 1 alpha（TEF-1α）基因的核酸序列比對鑑定為Fusarium proliferatum，並完成柯霍氏法則證明本菌對小花蕙蘭具有病原性。本病原菌最適菌絲生長與孢子發芽溫度分別為24-28℃與20-32℃。小花蕙蘭葉細斑病菌分離株（F. proliferatum Fp-172）可在四季蘭、報歲蘭及春蘭等品種嫩葉上造成細小褐色斑點，但在成熟葉片上則不造成病斑。另將此菌株的孢子懸浮液（10^6 spores mL^(-1)）噴施接種於四季蘭不同齡期幼芽葉片上，經28 d後，苗齡0.5、1.0、1.5、2.5、3.5及4.5 mo的幼芽罹病度分別為58.3-59.3%、52.8-62.5%、29.2-49.3%、13.9-25.9%、2.8-14.6%及0%，成熟葉片則無病斑產生。由細斑病菌易於感染1.5 mo內齡期幼芽的結果，可作為未來擬定葉細斑病防治時程之參考依據。

關鍵字

小花蕙蘭 ； 細斑病 ； 細斑病菌

並列摘要

Fleck spot disease is critical for oriental cymbidium cultivation owing to decreasing the appearance quality of plants. The main symptom is circular or irregular fleck lesions in black to brown on young leaves with or without a yellowish halo around the lesions. Occasionally in severe disease conditions, young shoots showed browning rot of basal leaves and shoot death. A species of fungus was isolated from the diseased tissue and identified as Fusarium proliferatum based on morphological characters, nucleotide sequence comparison of internal transcribed spacer (ITS), and translation elongation factor 1 alpha (TEF-1α) gene. Pathogenicity tests were carried out by artificial inoculation with conidial suspensions of the tested fungus to fulfill Koch's postulates. The optimal temperatures for mycelial growth and spore germination of F. proliferatum were 24-28℃ and 20-32℃ , respectively. Seven oriental cymbidium cultivars including Cymbidium ensifolium, C. sinense and C. goeringii, showed brown-to-black fleck lesions on young leaves, but no symptom appeared on mature leaves after artificial inoculation. To investigate the effect of shoot age on the susceptibility of fleck spot disease, potted oriental cymbidium (C. ensifolium 'Tsai-hong' cultivar) contained different ages of shoots were inoculated with conidial suspension at 28℃ . Results showed that disease severities of 0.5, 1.0, 1.5, 2.5, 3.5 and 4.5-month-old of shoots were 58.3-59.3%, 52.8-62.5%, 29.2-49.3%, 13.9-25.9%, 2.8-14.6% and 0%, respectively; whereas the adult shoots showed no fleck spot symptoms. The above results might provide the information for controlling fleck spot of oriental cymbidium caused by F. proliferatum.

並列關鍵字

Oriental cymbidium ； Fleck spot ； Fusarium proliferatum