Lamboy J S, Dillard H R
Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456.
Plant Dis. 1997 Feb;81(2):228. doi: 10.1094/PDIS.1997.81.2.228D.
In a commercial greenhouse in upstate New York, dark brown, angular lesions were first observed in April on lower, older leaves of 4-month-old tomato plants (Lycopersicon esculentum Mill. 'Jumbo'). Chlorosis frequently developed around the lesions. Removal of the infected leaves reduced the rate of epidemic development. However, by July, lesions were present throughout the plant canopy, up to 2 m. The irregularly shaped lesions varied in size from 1 to 5 mm, frequently with tan-colored centers initially. Conidia developed in the center of the lesions, primarily on the outer, or adaxial side of the leaf, but were infrequent on the abax-ial surface. This contrasts with Cladosporium leaf mold caused by Fulvia fulva, in which the conidia develop as a velvety brown patch in lesions on the abaxial, or underside of the leaf, accompanied by chlorosis on the upper side of the leaf (1). The conidia ranged in shape from oval or li-moniform (5 to 6 μm in diameter) to cylindrical (5 to 6 μm wide, 7 to 20 μm long). The fungus was identified as Cladosporium oxysporum Berk. & M. A. Curtis (3) by C. J. K. Wang and J. M. McKemy of the State University of New York College of Environmental Science and Forestry in Syracuse, NY. Koch's postulates were fulfilled with a tuft of mycelium and conidia grown on potato dextrose agar as inoculum on fully expanded leaves of 5-week-old tomato plants, cv. Jumbo. Two weeks later, characteristic sporulating lesions developed on inoculated plants, about 1 cm from the inoculation site. Within 3 weeks, in the research greenhouse, the disease spread to healthy tomato plants in the vicinity, confirming the highly infectious nature observed in the commercial greenhouse. The fungus was reisolated from inoculated leaves and also from the adjacent naturally infected plants. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and also a storage disease of ripe tomato fruit (4). To the best of our knowledge this is the first report of C. oxysporum causing disease on tomato foliage. References: (1) E. E. Chamberlain. N.Z. J. Agric. 45:136, 1932. (2) A. M. Hammouda. Plant Dis. 76:536, 1992. (3) J. M. McKemy and G. Morgan-Jones. Mycotaxon 41:397, 1991. (4) S. Singh et al. Indian J. Microbiol. 23:133, 1983.
在纽约州北部的一个商业温室里，4月份首次在4个月大的番茄植株（番茄品种“巨型”）下部较老的叶片上观察到深褐色的角状病斑。病斑周围经常出现黄化现象。摘除感染的叶片降低了病害流行的速度。然而，到了7月，整个植株冠层都出现了病斑，高度达2米。病斑形状不规则，大小从1毫米到5毫米不等，最初病斑中心常常呈棕褐色。分生孢子在病斑中心形成，主要在叶片的外侧或正面，但在叶片背面很少见。这与由番茄褐孢霉引起的枝孢叶霉病不同，在枝孢叶霉病中，分生孢子在叶片背面或下侧的病斑上形成天鹅绒状褐色斑块，同时叶片上侧出现黄化现象（1）。分生孢子的形状从椭圆形或柠檬形（直径5至6微米）到圆柱形（宽5至6微米，长7至20微米）不等。纽约州锡拉丘兹环境科学与林业学院的C. J. K. 王和J. M. 麦克凯米将这种真菌鉴定为尖孢枝孢菌（3）。用在马铃薯葡萄糖琼脂上培养的一束菌丝体和分生孢子作为接种物，接种到5周大的番茄品种“巨型”完全展开的叶片上，证实了柯赫氏法则。两周后，接种的植株在距接种部位约1厘米处出现了典型的产孢病斑。3周内，在研究温室中，病害传播到了附近健康的番茄植株上，证实了在商业温室中观察到的高传染性。从接种的叶片以及相邻的自然感染植株上再次分离到了该真菌。尖孢枝孢菌此前被报道为辣椒叶斑病（2）以及成熟番茄果实贮藏期病害（4）的病原菌。据我们所知，这是关于尖孢枝孢菌引起番茄叶片病害的首次报道。参考文献：（1）E. E. 张伯伦。《新西兰农业杂志》45:136，1932年。（2）A. M. 哈穆达。《植物病害》76:536，1992年。（3）J. M. 麦克凯米和G. 摩根 - 琼斯。《真菌分类学》41:397，1991年。（4）S. 辛格等人。《印度微生物学杂志》23:133，1983年。
