Acacia crassicarpa is a legume tree of rapid growth and high pulp yield and fibre quality, making this species the basis of large commercial plantations for pulpwood production in Southeast Asian countries. Since a disease has caused significant economic losses in a nursery in the province of Riau, Sumatra, Indonesia, this study aimed to identify the causal agent of the root rot, damping-off and wilting symptoms of A. crasicarpa seedlings. Isolations were made from infested soil by baiting with young leaves of native Quercus spp. from northern Sumatra. Classical identification using colony growth patterns and morphological characters, molecular identification based on ITS sequence analysis and direct PCR with specific primers, and pathogenicity tests were performed. All isolates formed typical Pythium structures and had fast growth, with optimum and maximum temperatures of 35 and 42°C, respectively. ITS sequence analysis of seven selected isolates showed 99.7–99.9% homology with Pythium myriotylum, the causal agent of nursery diseases on many crops. In addition, species-specific primers Pmy5/ITS2 successfully yielded an expected amplicon of approximately 144 bp. A soil infestation trial under controlled conditions confirmed the pathogenicity of P. myriotylum to A. crassicarpa, with typical symptoms starting six days after inoculation. The pathogen was re-isolated only from diseased inoculated plants fulfilling Koch's postulates. This is the first report of P. myriotylum as a pathogen on A. crassicarpa.

中文翻译：

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Pythium myriotylum 在印度尼西亚苏门答腊的相思树上引起的阻尼、根腐病和萎蔫

Acacia crassicarpa是一种生长迅速、纸浆产量和纤维质量高的豆科植物，使该物种成为东南亚国家纸浆木材生产的大型商业种植园的基础。由于疾病在印度尼西亚苏门答腊廖内省的苗圃中造成了重大经济损失，因此本研究旨在确定A根腐病、猝倒和枯萎症状的病原体。 紫荆幼苗。通过用本地栎树的幼叶作为诱饵，从受侵染的土壤中分离属 来自苏门答腊北部。使用菌落生长模式和形态特征进行经典鉴定，基于ITS序列分析和使用特异性引物的直接PCR进行分子鉴定，并进行致病性测试。所有分离株都形成了典型的腐霉结构并且生长迅速，最适和最高温度分别为 35 和 42°C。七个选定的分离株的 ITS 序列分析显示与Pythium myriotylum具有 99.7-99.9% 的同源性，后者是许多作物苗圃病害的病原体。此外，物种特异性引物 Pmy5/ITS2 成功产生了大约 144 bp 的预期扩增子。在受控条件下进行的土壤侵染试验证实了P的致病性。 肉豆蔻到A。 crassicarpa，接种后六天开始出现典型症状。病原体仅从符合科赫假设的患病接种植物中重新分离。这是P的第一份报告。 myriotylum作为A上的病原体。 厚果。