Code: OIV 455-1

Name: Leaf: degree of resistance to powdery mildew (leaf disc test)

Category: , GROUP OF CHARACTERISTICS, ORGAN

Subcategory: POWDERY MILDEW, BIOTIC RESISTANCE - FUNGUS, LEAF - MATURE, LEAF - YOUNG

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Description

The resistance of grapevine varieties to powdery mildew (Erysiphe necator) is to be observed under field trials over several years without the use of chemical plant protection and/or resistance inductors. - Observation of young leaves during the entire growing season on vines without fungicide treatment. - Application of dry fungus spore inoculum to the upper side of leaf discs of 20 mm of diameter and placed in Petri dishes using a brush. - About 1,000 spores per leaf disc is ideal; the density can be monitored by randomly placing microscope cover glasses among the leaf discs and counting spores under a binocular scope. - Incubation: 12 days at 23 °C and long day conditions (16 h light of 70 µE/m² sec corresponding to 3,000 Lux). - Place leaf discs of example varieties as control samples every 4-5 culture dishes. The symptoms should be evaluated considering the climatic conditions, that could influence the evolution of the disease, and, possibly, on plants without any biotic or abiotic stresses.

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