Yu F-Y, Niu X-Q, Tang Q-H, Zhu H, Song W-W, Qin W-Q, Lin C-H
Coconut Research Institute, Chinese Academy of Tropical Agricultural Sciences, Wenchang 571339, Hainan Province, China.
Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou 571737, China. The project was partially funded by the Special Fund for Agro-Scientific Research in the Public Interest (20090326) and the Opening Foundation (PDCTA1002) of Hainan State Key Laboratory for the Surveillance and Control of Tropical Agricultural Products.
Plant Dis. 2012 Feb;96(2):290. doi: 10.1094/PDIS-10-11-0840.
Stem bleeding of coconut was discovered in 2009 in Hainan, China. Affected trunk areas exhibited dark discoloration and a reddish brown or rust-colored liquid bleeding from different points. Stem tissues under the lesions rotted and became brownish yellow to black. Affected plants died within 3 to 4 months after stem symptoms first appeared. Stem bleeding of coconut is known to occur in production areas worldwide. The disease was first reported in Sri Lanka (1), caused severe damage to PB-121 hybrids in Indonesia (2), and is now known to occur in many other coconut-producing countries. However, to our knowledge, this is the first report of the disease in China. A fungus was isolated from lesion margins of diseased coconut trees. Colonies on potato dextrose agar (PDA) were white, became black 1 to 2 days later, and emitted a strong, fruity aroma. The fungus produced conidia, which were cylindrical, colorless to pale brown, and 6.9 to 14.9 × 3.1 to 6.0 μm, and oval, black chlamydospores that were 7.9 to 19.4 × 4.6 to 11.0 μm. The optimum temperature for mycelial growth ranged from 25 to 35°C and it did not grow at temperatures lower than 5°C or higher than 40°C. On the basis of these characteristics, the fungus was identified as Ceratocystis paradoxa (Dade) C. Moreau (anamorph Thielaviopsis paradoxa (de Seynes) Höhn). The internal transcribed spacer (ITS) region was amplified from genomic DNA with primers ITS1 and ITS4 and the PCR products were sequenced (GenBank Accession No. JQ039332). BLAST analysis showed 99% sequence similarity with C. paradoxa (GenBank Accession No. HQ248205.1). Pathogenicity of the fungus was tested by inoculating 10, 3-year-old coconut trees of the cv. green tall at the 12-leaf stage in the field. Agar plugs (5 mm in diameter) from the periphery of 7-day-old C. paradoxa colonies grown on PDA were placed on healthy trunks, rachis, and leaves, which were either wounded or unwounded. Wounds were made with a sterilized cork borer. Sites of the inoculations were wrapped with plastic tape to prevent desiccation; the experiment was repeated three times. Controls received plain PDA discs. Two weeks after inoculation, characteristic rusty brown lesions appeared only on wounded plants that were inoculated with the fungus. A brownish liquid oozed from the points of inoculation. Controls did not show signs of disease development. C. paradoxa was reisolated from the diseased tissues. Infection occurred on wounded sites only, suggesting that wounds may be required for infection. To prevent stem bleeding of coconut trees by C. paradoxa, vigilant cultural practices must be maintained to avoid causing wounds on the trees. References: (1) S. A. Alfieri. Plant Pathol. Circular No. 53. Florida Department of Agriculture Division of Plant Industry, 1967. (2) D. R. N. Warwick and E. E. M. Passos. Trop. Plant Pathol. 34:175, 2009.
2009年在中国海南发现了椰子茎流胶病。受影响的树干区域呈现出颜色变深，有红棕色或锈色液体从不同部位渗出。病斑下方的茎组织腐烂，变成棕黄色至黑色。受影响的植株在茎部症状首次出现后的3至4个月内死亡。已知椰子茎流胶病在全球各产区均有发生。该病最早在斯里兰卡被报道（1），在印度尼西亚对PB - 121杂交种造成了严重损害（2），现在已知在许多其他椰子生产国也有发生。然而，据我们所知，这是该病害在中国的首次报道。从患病椰子树的病斑边缘分离出一种真菌。在马铃薯葡萄糖琼脂（PDA）培养基上的菌落最初为白色，1至2天后变为黑色，并散发出强烈的水果香味。该真菌产生分生孢子，分生孢子呈圆柱形，无色至浅棕色，大小为6.9至14.9×3.1至6.0μm，还有椭圆形的黑色厚垣孢子，大小为7.9至19.4×4.6至11.0μm。菌丝体生长的最适温度范围为25至35°C，在低于5°C或高于40°C的温度下不生长。基于这些特征，该真菌被鉴定为奇异长喙壳菌（Ceratocystis paradoxa (Dade) C. Moreau）（无性型为奇异根串珠霉（Thielaviopsis paradoxa (de Seynes) Höhn））。用引物ITS1和ITS4从基因组DNA中扩增出内部转录间隔区（ITS）区域，并对PCR产物进行测序（GenBank登录号为JQ039332）。BLAST分析显示其与奇异长喙壳菌（GenBank登录号为HQ248205.1）的序列相似性为99%。通过在田间对10株12叶期的3年生绿矮种椰子树进行接种来测试该真菌的致病性。将在PDA培养基上培养7天的奇异长喙壳菌菌落边缘的琼脂块（直径5mm）放置在健康的树干、叶轴和叶片上，这些部位有的进行了创伤处理，有的未处理。用消毒后的钻孔器造成伤口。接种部位用塑料带包裹以防止干燥；该实验重复进行了三次。对照组接种普通PDA圆盘。接种两周后，只有接种了真菌的创伤植株上出现了典型的锈褐色病斑。接种点有褐色液体渗出。对照组未表现出病害发展的迹象。从患病组织中再次分离出奇异长喙壳菌。感染仅发生在创伤部位，这表明感染可能需要伤口。为防止奇异长喙壳菌引起椰子树茎流胶病，必须保持警惕的栽培管理措施，避免对树体造成伤口。参考文献：（1）S. A. Alfieri。植物病理学通报第53号。佛罗里达州农业植物产业司，1967年。（2）D. R. N. Warwick和E. E. M. Passos。热带植物病理学34:175，2009年。
