柑桔叶点霉侵染琯溪蜜柚的超微结构观察及致病机理分析

Destruction Characteristics of Hypodermal Cells in Citrus grandis ‘Guanximiyou’ Infected by Phyllosticta citriasiana and Pathogenic Mechanism

摘要:

为探明黑斑病对琯溪蜜柚（Citrus grandis ‘Guanximiyou’）果皮细胞的侵染破坏特点及作用机理，人工接种柑橘叶点霉亚洲种（Phyllosticta citriasiana）后，在扫描电镜与透射电镜下观察蜜柚真皮细胞的变化。结果表明，受到侵染后，真皮细胞的液泡膜首先发生褶皱、断裂，最终消失；叶绿体的淀粉粒消失、膜出现褶皱；质膜内陷、局部断裂；类囊体发生膨胀并解体；线粒体数量明显增加，基粒清晰可见，之后线粒体形态改变，双层膜消失，内部空胞化。未观察到细胞间隙及细胞内有菌丝分布，且细胞壁结构始终稳定。P.citriasiana危害蜜柚果皮细胞与毒素作用有关，侵染位点可能是细胞膜，信息通过胞间连丝穿过细胞壁，进入细胞内部。

Abstract:

In order to explore the characteristics of infection and damage of citrus black spot to Citrus grandis ‘Guanximiyou’, the changes in hypodermal cell structure were observed under scanning electron microscopy and transmission electron microscopy (TEM) after artificially inoculated with Phyllosticta citriasiana. After pomelo fruits were infected, the tonoplast in hypodermal cell wrinkled, fractured, and eventually vanished. The starch grains in chloroplast disappeared. The plasmolemma wrinkled, invaginated and partly ruptured. The number of mitochondria increased with clear visible grana. The thylakoid swelled and disintegrated. Afterwards, mitochondria underwent morphological changes, including disappearance of two layers of membrane and vacuolization. However, there were no intercellular or intracellular hyphae, and the cell wall remained structurally stable. Phyllosticta citriasiana infected hypodermal cells of ‘Guanximiyou’ through toxins, which probably attack cell membrane structure and cross over cell wall through plasmodesmata.