A histopathological study using one resistant and one susceptible clone ofEucalyptus urophylla × Eucalyptus grandishybrid showed that the colonization ofCeratocystis fimbriatawas limited by rapid and intense host defense responses such as closure of the vessel pits; formation of tyloses and gels; accumulation of amorphous material, starch, phenolic compounds, and calcium oxalate; and tissue lignification. The defense mechanisms of the resistant clone were not lethal to the pathogen because the fungus was reisolated from the diseased tissue. The use of resistant genotypes of eucalypt is widely used to control Ceratocystis wilt caused by Ceratocystis fimbriata. However, little is known regarding the fungal infection process and the host defense responses. Thus, the objectives of this study were to compare the histopathological responses of one resistant and one susceptible clone of Eucalyptus urophylla × Eucalyptus grandis to artificial inoculation with C. fimbriata and to identify possible host defense responses against fungal infection. Fungal colonization was analyzed by light and scanning electron microscopy. The host defense responses to artificial fungal inoculation were evaluated through histochemical analysis and determining of the lignin concentration and lesion lengths, whereas the pathogen viability was confirmed by reisolations. Both tested clones showed similar responses against fungal infection but presented defense responses with different speeds and intensities. Fungal colonization was not restricted in the tissue of plants from the susceptible clone, whereas in the resistant clone, fungal colonization was limited to the xylem vessels and parenchyma around the vessels due to closure of the vessel pits; intense formation of tyloses and gels; accumulation of amorphous material, starch, phenolic compounds, and calcium oxalate; and tissue lignification. However, the fungus was reisolated from the inoculated tissues of both clones. The resistance of eucalypt cuttings was found to be based on the rapid and intense defense responses shaped by biochemical and structural mechanisms that contained fungal colonization in the xylem vessels and parenchyma tissues.

中文翻译：

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Eucalyptus urophylla × Eucalyptus grandis 抗性和易感性杂种克隆对 Ceratocystis fimbriata 感染的反应

使用 Eucalyptus urophylla × Eucalyptus Grandishybrid 的一个抗性和一个易感克隆进行的组织病理学研究表明，Ceratocystis fimbriatawas 的定植受到快速和强烈的宿主防御反应（例如血管凹坑的关闭）的限制；形成tyloses和凝胶; 无定形物质、淀粉、酚类化合物和草酸钙的积累；和组织木质化。抗性克隆的防御机制对病原体并不致命，因为真菌是从患病组织中重新分离出来的。利用桉树的抗性基因型广泛用于防治由毛角囊藻引起的角囊藻枯萎病。然而，关于真菌感染过程和宿主防御反应知之甚少。因此，本研究的目的是比较一种抗性和一种易感的 Eucalyptus urophylla × Eucalyptus grandis 克隆对 C. fimbriata 人工接种的组织病理学反应，并确定针对真菌感染的可能宿主防御反应。通过光学和扫描电子显微镜分析真菌定植。通过组织化学分析和确定木质素浓度和病变长度来评估宿主对人工真菌接种的防御反应，而病原体的生存能力则通过重新隔离来确认。两个测试的克隆对真菌感染表现出相似的反应，但表现出不同速度和强度的防御反应。真菌定植在易感克隆的植物组织中不受限制，而在抗性克隆中，由于血管凹坑的关闭，真菌定植仅限于木质部血管和血管周围的薄壁组织；tyloses 和凝胶的强烈形成; 无定形物质、淀粉、酚类化合物和草酸钙的积累；和组织木质化。然而，真菌是从两个克隆的接种组织中重新分离出来的。发现桉树插条的抗性基于由木质部血管和薄壁组织中真菌定植的生化和结构机制形成的快速和强烈的防御反应。从两个克隆的接种组织中重新分离出真菌。发现桉树插条的抗性基于由木质部血管和薄壁组织中真菌定植的生化和结构机制形成的快速和强烈的防御反应。从两个克隆的接种组织中重新分离出真菌。发现桉树插条的抗性基于由木质部血管和薄壁组织中真菌定植的生化和结构机制形成的快速和强烈的防御反应。