Analysis of P. viticola infection steps. Infected leaf disks from V. vinifera (left panels) and V. riparia (right panels) were collected at 12, 24, 48 and 96 hpi, stained with 0.05% aniline blue and observed under an epifluorescence microscope. Panels A, B, C, D and F: magnification 200×; panels E, G and H: magnification 100×. Arrows indicate primary hyphae, arrowheads haustoria. Bars = 80 μm.