University of California, Department of Botany and Plant Sciences, Riverside, CA 92521.
USDA Forest Service, Forest Products Laboratory, Madison, WI 53726.
Phytopathology. 2022 Feb;112(2):345-354. doi: 10.1094/PHYTO-03-21-0107-R. Epub 2022 Feb 3.
The number of reports associated with wood dieback caused by fungi in the Botryosphaeriaceae in numerous perennial crops worldwide has significantly increased in the past years. In this study, we investigated the interactions between the canker pathogen and the almond tree host (), with an emphasis on varietal resistance and host response at the cell wall biochemical and histological levels. Plant bioassays in a shaded house showed that among the four commonly planted commercial almond cultivars ('Butte', 'Carmel', 'Monterey', and 'Nonpareil'), there was no significant varietal difference with respect to resistance to the pathogen. Gummosis was triggered only by fungal infection, not by wounding. A two-dimensional nuclear magnetic resonance and liquid chromatography determination of cell wall polymers showed that infected almond trees differed significantly in their glycosyl and lignin composition compared with healthy, noninfected trees. Response to fungal infection involved a significant increase in lignin, a decrease in glucans, and an overall enrichment in other carbohydrates with a profile similar to those observed in gums. Histological observations revealed the presence of guaiacyl-rich cell wall reinforcements. Confocal microscopy suggested that colonized mainly the lumina of xylem vessels and parenchyma cells, and to a lesser extent the gum ducts. We discuss the relevance of these findings in the context of the compartmentalization of decay in trees model in almond and its potential involvement in the vulnerability of the host toward fungal wood canker diseases.
近年来，全球众多多年生作物中由 Botryosphaeriaceae 真菌引起的木材枯萎病相关报告数量显著增加。在这项研究中，我们研究了溃疡病原菌与杏仁树宿主之间的相互作用，重点研究了品种抗性和细胞壁生化及组织学水平的宿主反应。遮荫室内的植物生物测定表明，在四种常见种植的商业杏仁品种（“巴特”、“卡梅尔”、“蒙特雷”和“诺帕内尔”）中，对病原菌的抗性没有显著的品种差异。流胶病仅由真菌感染引发，而非由创伤引发。细胞壁聚合物的二维核磁共振和液相色谱测定表明，与健康、未感染的树木相比，感染杏仁树的糖基和木质素组成有显著差异。对真菌感染的反应涉及木质素的显著增加、葡聚糖的减少以及其他碳水化合物的整体富集，其特征与在树胶中观察到的相似。组织学观察显示存在愈创木基丰富的细胞壁加固物。共聚焦显微镜表明，主要定植于木质部导管和薄壁细胞的腔室，以及胶管的腔室，程度较小。我们讨论了这些发现与杏仁树中腐烂的分隔模型以及它们可能与宿主对真菌性木材溃疡病的易感性的相关性。
