PSEUDOPEZICULA TRACHEIPHILA ON VITIS-VINIFERA - MICROSCOPIC STUDIES OF THE INFECTION MECHANISM

Electron microscopical studies of Rotbrenner pathogenesis revealed tha t the fungus predominantly penetrates the anticlinal cell walls of the host. Appressorium formation is not required for penetration. To impr ove attachment to the host surface, the infection hypha forms mucous p ad. As defense reaction, secondary deposits of the cell walls of the a djacent epidermal cells were observed. After penetrating the epidermis cells, the fungus remains biotrophic. In the second stage of disease development, the biotrophic relationship between the pathogen and the host changes to perthotrophic. Near the infection sites, flavan-3-ols are localized in vacuolar inclusions of the parenchyma cells. In the s pongy parenchyma, the mycelium of Pseudopezicula tracheiphila grows in tracellularly with accompanying destruction of the host cells. The myc elium was detected in xylem vessels as well as in parenchymatic cells of xylem and phloem. After the hyphae invaded the vessel elements, adj acent parenchyma cells form tyloses.