Bardas G A, Tziros G T, Tzavella-Klonari K
Aristotle University of Thessaloniki, Faculty of Agriculture, Plant Pathology Laboratory, P.O. Box 269, 541 24, Thessaloniki, Greece.
Plant Dis. 2008 Apr;92(4):653. doi: 10.1094/PDIS-92-4-0653C.
Common bean (Phaseolus vulgaris L.) is cultivated extensively in Greece for dry and fresh bean production. During 2005 and 2006, a disease with typical blight symptoms was observed occasionally on dark red kidney, brown kidney, and black bean plants in most bean-producing areas of Greece. It rarely was destructive unless the crop had been weakened by some unfavorable environmental conditions. Infected leaves had brown-to-black lesions that developed concentric zones 10 to 30 mm in diameter and also contained small, black pycnidia. Concentric dark gray-to-black lesions also appeared on branches, stems, nodes, and pods. Infected seeds turned brown to black. Plants sometimes showed defoliation and pod drop. The fungus was consistently isolated on potato dextrose agar from diseased leaves and pods and identified as Phoma exigua var. exigua Sutton and Waterstone on the basis of morphological characteristics of conidia and pycnidia (1,2). Spores were massed in pycnidia from which they were forced in long, pink tendrils under moist weather conditions. Conidia were cylindrical to oval, allantoid, hyaline, pale yellow to brown, usually one-celled, and 2 to 3 × 5 to 10 μm. To satisfy Koch's postulates, a conidial suspension (1 × 10 conidia per ml) of the fungus was sprayed onto leaves and stems of bean seedlings (first-leaf stage) (cv. Zargana Hrisoupolis). Both inoculated and control seedlings (inoculated with sterile water) were covered with plastic bags for 72 h in a greenhouse at 23°C. Inoculated plants showed characteristic symptoms of Ascochyta leaf spot 12 to 15 days after inoculation. The fungus was reisolated from lesions that developed on the leaves and stems of all inoculated plants. The pathogen is present worldwide on bean. To our knowledge, this is the first report of P. exigua var. exigua on common bean in Greece. References: (1) D. F. Farr et al. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. ARS, USDA, 2007. (2) B. C. Sutton and J. M. Waterstone. Ascochyta phaseolorum. No. 81 in: Descriptions of Pathogenic Fungi and Bacteria. CMI/AAB, Kew, Surrey, England, 1966.
菜豆（Phaseolus vulgaris L.）在希腊广泛种植，用于生产干豆和鲜豆。在2005年和2006年期间，希腊大多数豆类产区的暗红色菜豆、褐芸豆和黑豆植株上偶尔观察到一种具有典型疫病症状的病害。除非作物因某些不利的环境条件而生长衰弱，否则这种病害很少具有毁灭性。受感染的叶片有褐色至黑色的病斑，病斑形成直径10至30毫米的同心环带，病斑上还含有小的黑色分生孢子器。树枝、茎、节和豆荚上也出现同心的深灰色至黑色病斑。受感染的种子变为褐色至黑色。植株有时会出现落叶和落荚现象。始终能从患病叶片和豆荚上在马铃薯葡萄糖琼脂培养基上分离到该真菌，并根据分生孢子和分生孢子器的形态特征将其鉴定为小茎点霉小茎点变种（Sutton and Waterstone）（1,2）。孢子聚集在分生孢子器中，在潮湿天气条件下会从分生孢子器中挤出形成长长的粉红色细丝。分生孢子圆柱形至椭圆形，腊肠形，透明，浅黄色至褐色，通常单细胞，大小为2至3×5至10微米。为了验证科赫法则，将该真菌的分生孢子悬浮液（每毫升1×10个分生孢子）喷洒在菜豆幼苗（第一片叶期）（品种Zargana Hrisoupolis）的叶片和茎上。接种和对照幼苗（接种无菌水）在23°C的温室中用塑料袋覆盖72小时。接种的植株在接种后12至15天出现壳二孢叶斑病的典型症状。从所有接种植株的叶片和茎上出现的病斑中再次分离到该真菌。这种病原菌在世界各地的菜豆上都有存在。据我们所知，这是希腊关于小茎点霉小茎点变种侵染菜豆的首次报道。参考文献：（1）D.F. Farr等人，真菌数据库。系统植物学和真菌学实验室。在线出版物。美国农业部农业研究局，2007年。（2）B.C. Sutton和J.M. Waterstone。菜豆壳二孢。载于《病原真菌和细菌描述》第81号。英联邦真菌研究所/英联邦农业局，英国萨里郡邱园，1966年。
