鳳仙花露菌病之發生與其防治

Occurrence and control of Impatiens downy mildew in Taiwan

黃晉興(J.-H. Huang) ； 李佩如(P.-J. Li)

《植物病理學會刊》 24卷2期 (2015/06) Pp. 89-96

https://doi.org/10.6649/PPB.201506_24(2).0002

摘要

2013 年2 月在台灣彰化某苗圃的非洲鳳仙花（Impatiens walleriana）發生一種病害，罹病葉片正面呈現淡綠至黃化，無明顯壞疽病斑，葉背有白色黴狀物，生長勢弱且開花數減少，罹病葉片於病害後期褐化脫落，若於幼苗受感染則生長不良且易死亡。在顯微鏡下觀查葉背的黴狀物，發現該些微生物有透明樹枝狀的孢囊柄，大小為175-450×6.7-11 μm，孢囊柄末端有3 個小枝，大小為7.5-(10.4)-16.0 μm，小枝長出透明橢圓形的孢囊，大小為14.3-(18.5)-20.1×10.3-(14.1)-16.0 μm，每個孢囊於水中可釋放出數個至10 餘個游走子（zoospore），大小為7-9 μm。利用引子對NL1/NL4增幅出核醣體大次單元（large ribosomal subunit）的核酸並予以解序，其序列與GenBank網站登錄的數條鳳仙花露菌Plasmopara obducens 之序列有99-100%的相似度。將孢囊懸浮液接種於盆栽作物上，在20℃與密封高濕度的環境下10天後即出現與田間罹病株相同的病徵，且觀察得與原接種的病原菌形態相同的露菌，証實其病原性。經由病原菌形態、核酸序列比對與病原性，鑑定該菌為鳳仙花露菌P. obducens。以切離葉與盆栽接種結果顯示於6-24℃皆發病，最適發病溫度為12-20℃。以盆栽接種結果顯示該菌僅感染某些種類的鳳仙花而不感染其他草花，其中非洲鳳仙花、庭園鳳仙花（I. balsamina）以及新幾內亞鳯仙花（I. hawkeri）之發病度分別為65.0%、11.0%與0%。由田間藥劑防治試驗的結果顯示，病害初期每週1次噴灑供試藥劑於葉片，噴灑4次後，鋅錳滅達樂、本達樂或亞磷酸+氫氧化鉀之處理其發病度＜1%，與對照組之98.2%有顯著差異，唯須注意停止施藥2-3週後則再度發病。

關鍵字

非洲鳳仙花 ； 露菌病 ； 防治

並列摘要

In February 2013, diseased Impatiens walleriana plants were observed in nurseries in Changhua county, central Taiwan. The adaxial side of leaves was pale green to yellow without distinct lesions. White downy appeared on the abaxial side and flower buds. The number of flowers was obviously reduced. In the late disease stage, the infected leaves became brown and abscised from the stem. When young plants and seedlings were infected, they generally didn't survive. Microscopic observations of the infected leaves disclosed the hyaline, tree-like, 175-450×6.7-11μm sporangiophores, with three apical branchlets, 7.5-(10.4)- 16.0 μm. Sporangia were hyaline, oblong, 14.3-(18.5)-20.1×10.3-(14.1)-16.0 μm. Zoospores formed in sporangia and released out of them, cysts 7-9 μm. The DNA sequences encoding the large ribosomal subunit (LSU rDNA), being amplified using primers NL1 and NL4 and then sequenced, were 99-100% identical to the sequences of several Plasmopara obducens isolates deposited in GenBank. Inoculation of detached leaves and potted plants with sporangia suspension resulted in the same white downy symptoms after 10 days of inoculation at 20℃, which confirmed the pathogenicity. Based on morphological, molecular and pathogenic characters, the pathogen was identified as P. obducens. In the detached leaves and potted plants inoculation trials, the disease could develop at 6-24℃, optimally at 12-20℃. The host range tests showed that the pathogen infected only certain Impatiens spp. The levels of disease severities on potted I. walleriana, I. balsamina and I. hawker were 65.0%, 11.0% and 0% respectively. In the field tests, mancozeb+metalaxyl, benalaxyl, and phophorous acid + potassium hydroxide effectively controlled the disease. After 4 times of spraying at one week interval, the treated plants showed ＜1% disease severity, compared to 98.2% disease severity observed from the blank control. However, the disease occurred again 2-3 weeks after the last application of the chemicals.

並列關鍵字

Impatiens walleriana ； Plasmopara obducens ； control