Garibaldi A, Minuto A, Gullino M L
Centre of Competence for the Innovation in the Agro-Environmental Sector (AGROINNOVA) Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Plant Dis. 2005 Nov;89(11):1243. doi: 10.1094/PD-89-1243B.
Iberis sempervirens (candytuft) is increasingly grown in Liguria (northern Italy) as a potted plant for ornamental purposes, particularly under cool-weather conditions. At the end of the summer of 2003, extensive necrosis was observed on leaves and young stems of 4-month-old plants grown in 14-cm diameter pots outdoors at a commercial farm. In many cases, on the upper side of the leaves, necrotic spots were surrounded by a chlorotic halo that turned progressively black. The necrotic areas often coalesced, generating larger and irregularly shaped spots. On the lower side of the leaves, no chlorotic areas were observed. Severely affected plants were defoliated. Infected plants rarely died, but the presence of lesions on mature plants decreased aesthetic quality and subsequently market value. The disease occurred on 40% of plants at each of the two farms. Leaf spots contained dark brown, multicellular pear-shaped conidia. Conidia were 22.5 to 50.0 μm (average 32.8 μm) long and 7.5 to 15.0 μm (average 12.3 μm) wide, with 5 to 7 longitudinal cross walls and an average of 6 to 7 single cells. From infected leaves, a fungus identified on the basis of its morphological characteristics as Alternaria sp. was consistently isolated on potato dextrose agar. Pathogenicity tests were performed by spraying leaves of healthy 12-month-old potted I. sempervirens plants with a spore and mycelial suspension (10 CFU/ml). Plants without inoculation served as control. Ten plants were used for each treatment. Plants were covered with plastic bags for 10 days after inoculation and kept outdoors for 60 days at temperatures ranging from 0 to 32°C (average 12°C). The first lesions developed on leaves 45 days after inoculation, while control plants remained healthy. From such lesions, Alternaria sp. was consistently reisolated. The pathogenicity test was carried out twice. The presence of A. brassicae was reported in Tanganica on Iberis sp., I. umbellata in Denmark (2), and I. amara in the United States (4); A. matthiolae was observed on seeds of I. amara and I. umbellata (3). A leaf spot incited by Alternaria sp. on I. amara was observed in Florida (1). This is, to our knowledge, the first report of Alternaria sp. on I. sempervirens in Italy as well as worldwide. References: (1) S. A. Alfieri et al. Index of Plant Diseases in Florida. Bull. 11, 1984. (2) P. Neergaard. Rev. Appl. Micol. 18:572, 1939. (3) P. Neergaard. Rev. Appl. Micol. 25:382, 1946). (4) R. D. Raabe. Comb. Proc. Int. Plant Propagators Soc. 40:160, 1991.
常夏石竹（屈曲花）在利古里亚（意大利北部）越来越多地作为盆栽观赏植物种植，特别是在凉爽天气条件下。2003年夏末，在一个商业农场户外种植于直径14厘米花盆中的4个月大植株的叶片和嫩茎上观察到大面积坏死。在许多情况下，叶片上侧的坏死斑被黄化晕圈包围，黄化晕圈逐渐变黑。坏死区域常常融合，形成更大的不规则形状斑点。在叶片下侧未观察到黄化区域。受严重影响的植株落叶。受感染的植株很少死亡，但成熟植株上病斑的存在降低了美观度，进而降低了市场价值。两个农场中每个农场40%的植株发病。叶斑中含有深褐色、多细胞梨形分生孢子。分生孢子长22.5至50.0微米（平均32.8微米），宽7.5至15.0微米（平均12.3微米），有5至7个纵向横壁，平均有6至7个单细胞。从受感染叶片上，在马铃薯葡萄糖琼脂上持续分离出一种根据其形态特征鉴定为链格孢属的真菌。通过向健康的12个月大盆栽常夏石竹植株叶片喷洒孢子和菌丝悬浮液（10 CFU/ml）进行致病性测试。未接种的植株作为对照。每种处理用10株植株。接种后用塑料袋覆盖植株10天，并在0至32°C（平均12°C）的温度下在户外放置60天。接种后45天叶片上出现首批病斑，而对照植株保持健康。从这些病斑中持续重新分离出链格孢属。致病性测试进行了两次。在坦噶尼喀报道链格孢在屈曲花属植物上存在，在丹麦报道在伞形屈曲花上存在（2），在美国报道在窄叶屈曲花上存在（4）；在窄叶屈曲花和伞形屈曲花种子上观察到链格孢属的芸苔链格孢（3）。在佛罗里达观察到链格孢引起的窄叶屈曲花叶斑（1）。据我们所知，这是意大利以及世界范围内关于链格孢属在常夏石竹上的首次报道。参考文献：（1）S. A. 阿尔菲耶里等人。《佛罗里达植物病害索引》。通报11，1984年。（2）P. 尼尔高。《应用真菌学评论》18:572，1939年。（3）P. 尼尔高。《应用真菌学评论》25:382，1946年。（4）R. D. 拉贝。《国际植物繁殖者协会会议论文集》40:160，1991年。
