Ultrastructure and Cytochemistry of Pectin and Cellulose Degradation in Tobacco Roots Infected byPhytophthora parasiticavar.nicotianae

Root colonization of tobacco (Nicotiana tabacum L. Xanthi-nc') by the pathogen Phytophthora parasitica var nicotianae was studied by electron microscopy. Gold-complexed probes were used for the localization of pectin and cellulose. The epidermis was colonized from 24 to 48 h after inoculation, and the cortex appeared entirely colonized by the time the pathogen reached the paratracheal parenchyma (96 h after inoculation). The fungus did not penetrate the xylem vessels. Colonization of the root tissues was associated with changes, including alteration of primary cell walls and breakdown of middle lamella matrices (...)