ABSTRACT Acacia koa A. Gray (koa) is a leguminous timber wood tree endemic to the Hawaiian Islands. Koa forests have been suffering from a devastating wilt disease caused by the fungal pathogen Fusarium oxysporum f. sp. koae. To protect koa forestry from the disease, it is crucial to understand how disease resistance is conferred in koa. Here we show that non-wounding mechanical stress enhances resistance against F. oxysporum in koa as the survival rate of stressed seedlings doubled compared to that of unstressed seedlings (40.6% and 17.0%, respectively) following 3 weeks of mechanical treatment. The mechanical stress induces genes for antifungal activities, including those for pathogenesis-related (PR) proteins and phenylpropanoid biosynthesis enzymes, within six hours. Consistent with the gene expression, the extract from the stems of stressed plants had an increased total phenolic content as well as antifungal activity. Stressed plants also showed faster and enhanced expression of genes for the antifungal proteins upon inoculation by F. oxysporum f. sp. koae. These results indicate that a simple non-wounding mechanical stress can prime koa seedlings for the subsequent fungal infection to enhance disease resistance, and non-wounding mechanical stress may be a useful tool to study mechanisms underlying disease resistance in koa.

中文翻译：

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在机械胁迫的金合欢 A. 灰色幼苗中诱导对尖孢镰刀菌的抗性

摘要 Acacia koa A. Gray (koa) 是夏威夷群岛特有的豆科木材木材树。考阿森林一直遭受由真菌病原体尖孢镰刀菌 (Fusarium oxysporum f) 引起的毁灭性枯萎病。sp. 考埃。为了保护 koa 林业免受该病害，了解 koa 是如何赋予抗病能力的至关重要。在这里，我们表明非创伤性机械应力增强了 koa 对 F. oxysporum 的抵抗力，因为在经过 3 周的机械处理后，与未受胁迫的幼苗相比，受胁迫的幼苗的存活率翻了一番（分别为 40.6% 和 17.0%）。机械应力会在 6 小时内诱导抗真菌活性基因，包括致病相关 (PR) 蛋白和苯丙烷生物合成酶的基因。与基因表达一致，来自受胁迫植物茎的提取物具有增加的总酚含量以及抗真菌活性。受胁迫的植物在被尖孢镰刀菌 f 接种后也表现出更快和增强的抗真菌蛋白基因表达。sp. 考埃。这些结果表明，简单的非创伤性机械应力可以使 koa 幼苗为随后的真菌感染做好准备，以增强抗病性，并且非创伤性机械应力可能是研究 koa 抗病性机制的有用工具。