Garibaldi A, Bertetti D, Gullino M L
Centre of Competence AGROINNOVA, University of Torino, Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Plant Dis. 2007 Oct;91(10):1363. doi: 10.1094/PDIS-91-10-1363C.
The genus Clematis, belonging to the Ranunculaceae family, is widely used in gardens and is very much appreciated for its climbing attitude as well as rich flower production. In the fall of 2006, in a private garden located near Biella (northern Italy), a severe foliar disease was observed on 2-year-old plants of Clematis × jackmanii. Small necrotic spots were observed on the upper and lower sides of infected leaves. At temperatures of 15 to 25°C, spots enlarged to form round areas that were 2 to 7 cm in diameter and well defined by a brown margin. Severely infected leaves wilted without abscising. The disease occurred on 100% of the plants of the C. × jackmanii hybrid in one garden. Stems and flowers were not affected by the disease. From infected leaves, a fungus was consistently isolated on potato dextrose agar (PDA) amended with 25 mg/liter of streptomycin. The fungus was grown on PDA and maintained at 22°C (12-h light, 12-h dark). After 10 days, black pycnidia 132 to 340 μm in diameter developed, releasing abundant hyaline, elliptical, nonseptate, conidia measuring 5.1 to 8.3 (6.8) × 1.6 to 3.4 (2.7) μm. On the basis of its morphological characteristics, the fungus was identified as a Phoma sp. (2). The internal transcribed spacer region of rDNA was amplified using primers ITS4/ITS6 (1,3), sequenced (GenBank Accession No. EF566917), and identified as a Phoma sp. Pathogenicity tests were performed by spraying leaves of healthy 1-year-old potted C. × jackmanii (cvs. Superba, Mrs N. Thomson, and Vagebond) plants with a spore and mycelial suspension (4 × 10 spores or mycelial fragments per ml). Noninoculated plants served as controls. Five plants per cultivar were used for each treatment. Plants were covered with plastic bags for 3 days after inoculation and kept in a growth chamber at 18 to 20°C. Symptoms previously described developed on leaves of all tested cultivars 10 days after inoculation, while control plants remained healthy. On the infected leaves, pycnidia and conidia with the same dimensions and characteristics as previously described were observed. The fungus was consistently reisolated from the lesions of the inoculated plants. The pathogenicity test was carried out twice. The presence of Ascochyta clematidina, then renamed as Phoma clematidina, on Clematis species has been reported in the United States (4) and subsequently in the Netherlands, Britain, and New Zealand. References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema and G. J. Bollen. Persoonia 8:111, 1975. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) W. O. Gloyer. J. Agric. Res. 4:331, 1915.
铁线莲属植物隶属于毛茛科，在园林中广泛应用，因其攀援姿态及丰富的花量而备受喜爱。2006年秋，在意大利北部比耶拉附近的一座私人花园里，人们在两年生的杰克曼氏铁线莲植株上发现了一种严重的叶部病害。在受感染叶片的上表面和下表面均观察到小的坏死斑。在15至25°C的温度下，病斑扩大形成直径为2至7厘米的圆形区域，且由褐色边缘清晰界定。严重感染的叶片枯萎但未脱落。在一个花园中，该病害在杰克曼氏铁线莲杂交种的所有植株上均有发生。茎和花未受此病害影响。从受感染的叶片上，在添加了25毫克/升链霉素的马铃薯葡萄糖琼脂（PDA）上持续分离出一种真菌。该真菌在PDA上培养，并保持在22°C（12小时光照，12小时黑暗）条件下。10天后，形成了直径为132至340微米的黑色分生孢子器，释放出大量透明、椭圆形、无隔膜的分生孢子，其大小为5.1至8.3（6.8）×1.6至3.4（2.7）微米。基于其形态特征，该真菌被鉴定为茎点霉属的一个种（2）。使用引物ITS4/ITS6（1,3）扩增rDNA的内部转录间隔区，进行测序（GenBank登录号为EF566917），并鉴定为茎点霉属的一个种。通过向健康的一年生盆栽杰克曼氏铁线莲（品种有超级、N. 汤姆森夫人和瓦格邦德）植株的叶片喷洒孢子和菌丝体悬浮液（每毫升含4×10个孢子或菌丝片段）来进行致病性测试。未接种的植株作为对照。每个品种每种处理使用五株植株。接种后用塑料袋覆盖植株3天，并置于18至20°C的生长室中。接种10天后，所有测试品种的叶片上均出现了先前描述的症状，而对照植株保持健康。在受感染的叶片上，观察到了与先前描述尺寸和特征相同的分生孢子器和分生孢子。该真菌持续从接种植株的病斑中重新分离出来。致病性测试进行了两次。在美国（4）以及随后在荷兰、英国和新西兰均有报道在铁线莲属植物上存在铁线莲壳二孢菌，后更名为铁线莲茎点霉。参考文献：（1）S. F. Altschud等人，《核酸研究》25:3389，1997年。（2）G. H. Boerema和G. J. Bollen，《真菌学报》8:111，1975年。（3）D. E. L. Cooke和J. M. Duncan，《真菌研究》101:667，1997年。（4）W. O. Gloyer，《农业研究杂志》4:331，1915年。
