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Code: OIV 452

Name: Leaf: degree of resistance to downy mildew

Category: , GROUP OF CHARACTERISTICS, ORGAN

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

Description

The resistance of grapevine varieties to downy mildew (Plasmopara viticola) is to be observed under field trials over several years without the use of chemical plant protection and/or resistance inductors. Extension of infected mildew patches. The presence of symptoms on all the leaves from 4 - 6 vines has to be observed during the most virulent phases of the disease. 1 = Not limited, vast attacked patches or totally attacked leaf blades - strong fungus fructifications - pronounced and dense necrotic areas speckles- very early leaf drop. 3 = Vast, not limited attacked patches - very strong fungus fructification - numerous necrotic areas speckles - leaf drop not as early as with note 1. 5 = Limited attacked patches 1-2 cm in diameter - more or less severe fungus fructification – either numerous necrotic speckles and/or irregular formation of necrotic areas speckles. 7 = Less attacked patches - less fructification – frequent necrotic speckles. 9 = No symptoms, neither fructification nor necrotic speckles, or either punctuated or few necrotic speckles. 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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