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Seasonal Variation in Severity of Tomato Black Leaf Mold in Taiwan, Host Infection, and Conidia l Survival of Pseudocercospora fuligena

台灣番茄黑黴病的季節嚴重度、寄主感染及黑黴病菌

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摘要


由Pseudocercospora fuligena引起之番茄黑黴病廣泛地發生於熱帶及亞熱帶地區。有關本病害之季節嚴重度、影害進展之環境因子、病原菌侵染過程及分生孢子存活之研究很少。四個罹病番茄品種包括台中亞蔬四號、台南選二號、花蓮亞蔬五號及農友301,一年中每兩個月定植「一次在亞蔬中心試驗田,以調查每批定植的番茄受黑黴病危害之嚴重度。結果發現1994年9月中旬至1995年3月中旬期間之番茄遭受黑黴病危害最爲嚴重。每一次定植後調査期間所得之病害進展曲線下面積値與發生露水之天數及所收集之分生孢子總數呈顯著正相關。將P. fuligena分生孢子懸浮液(5 x 10^3 conidia/ml)噴霧接種於番茄葉放在培養皿内不鏽鋼網上後,在28 ± 2 C。定溫箱中經6及48小時後,發芽率分別爲71及99%。噴霧接種病原菌的分 生孢子懸浮液到番茄苗的葉片,經72及120小時後,發芽的分生孢子分別有10及31%產生發芽管自氣孔侵入。接種後第6天可見細小病斑開始出現。第11天可見灰白色分生孢柄自氣孔處長出,第12天,可見成熟分生孢柄及分生孢子。接種後之番茄苗放置高溼度(98 ± 2 % RH)生長室的期間由0天增加至4天時,在接種後第14天發現黑黴病感染危害之葉面積百分率由51%增加到96%。取黑黴病感染後之罹病葉片陰乾,再以塑膠袋包封並放置於4℃ 12C、20C、28C及32 C。的定溫箱中或室溫下;或將罹病葉片放於尼龍網袋中並安置在試驗田,其中一袋是懸吊於土表之上,另一袋則埋於土表下5cm。經過18個月後,儲存在 4 C、12 C丶 20 C。及室溫下的樣品仍有少數(<1%)分生孢子發芽,而樣品儲存在28 C。經17個月,32C。經13個月,懸吊於田間經7個月及埋入土裡經4個月後,分生孢子均無發芽。

並列摘要


Black leaf mold (BLM) of tomato caused by Pseudocercospora fuligena is widespread in the tropics and subtropics, but little is known about factors affecting disease development. In this study, four tomato varieties were planted in the field at 2-month intervals from February 1994 to April 1995 to estimate BLM severity throughout the year. BLM was most severe from mid September 1994 to mid March 1995. Area under disease progress curve (AUDPC) values calculated for each planting throughout the year were positively correlated with the number of dew days that occurred during each crop. The number of airborne conidia collected in the experimental plots during each tomato growth period was positively correlated with the AUDPC values for those periods. Germination of fuligena conidia on detached tomato leaves incubated at 28 ± 2 C was 71 and 99% after 6 and 48 hr, respectively. Germ tubes from 10 and 31% of the germinated conidia had penetrated stomata after 72 and 120 hr incubation, respectively. Lesions were first visible 6 days after inoculation. Light gray conidiophores emerged from stomatal openings 11 days after inoculation, and mature conidiophores and conidia were observed on the 12th day. As the time that inoculated plants were held at 98 t 2% RH was increased from 0 to 4 days, the percentage of leaf area affected by BLM 14 days after inoculation increased from 51 to 96%. Survival of conidia on air dried BLM-infected tomato leaves was determined after subsamples were maintained in plastic bags over a range of temperatures in the laboratory, and in nylon mesh bags above and below ground in the field. Some conidia germinated (<1%) after 18 mo from samples held at 4°, 12° and 20 C and room temperature. No germination occurred with conidia from 28 c storage after 17 mo, at or above 32 c after 13 mo. from above-ground field samples after 7 mo, nor buried samples after 4 mo.

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