Association of phenol-containing structures with Apium graveolens resistance to Fusarium oxysporum f.sp. apii race 2

Publisher Website
Google Scholar
Abstract
Electron-opaque (EO) structures were studied, using light and electron microscopy, in the xylem parenchyma cells and vessels of both incompatible and compatible Apium graveolens L. var. rapaceum (celeriac) and compatible Apium graveolens L. var. dulce (celery) roots 24 h after inoculation with Fusarium oxysporum f.sp. apii race 2. Few small EO bodies were observed in the noninoculated hosts. Histological, cytochemical, and chemical tests indicated the presence of phenolic substances and polysaccharides in the EO materials. These EO structures increased both in number and size as infection progressed. The incompatible host produced three and five times more of the EO materials than the compatible celeriac and celery, respectively. The amount of the EO materials and host compatibility were related to the absence and presence of fungal hyphae in the vascular system. Hyphae either associated with or enveloped by the EO structures were vacuolated; their cytoplasm was restricted to the cell periphery. Occlusion of the xylem vessel pores of the incompatible host with the EO structures likely prevented upward spread of the pathogen throughout the entire plant.