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Code: OIV 458-1

Name: Leaf: degree of resistance to grey mould (laboratory analysis)

Category: , GROUP OF CHARACTERISTICS, ORGAN

Subcategory: GREY MOULD, BIOTIC RESISTANCE - FUNGUS, LEAF - MATURE, LEAF - YOUNG

Description

The resistance of grapevine varieties to grey mould (Botrytis cinerea) is to be observed under field trials over several years without the use of chemical plant protection and/or resistance inductors. Leaf material: - Sampling time at flowering until 4 weeks after flowering on non-sprayed vines. 6th distal leaf with petiole, counted from the first unfolded leaf. Make sure that the 6th leaves of the cultivars to be evaluated are at the same physiological age. Repetition with 3 leaves per variety Material: - Botrytis cinerea mycelium developed on Agar-culture. - Two high-grade steel borers (not brass, because zinc and copper inhibit fungus development) with a diameter of about 3 mm and 6 mm. - Wooden panels for stamping. - Metal tray and screen. Infection: - Punch out 3 holes per leaf between the main veins with the 3 mm borer. Punch out a hole in the Botrytis mycelium at the Petri dish edges, where the fungus grows more actively, with the 6 mm borer. The leaves are suspended above water on a screen placed in the tray so that only their petioles are submerged. Place the inoculum plug, mycelium downwards, on the leaf hole. Place an agar plug without fungus on one leaf hole as a control. Store in the dark at room temperature (about 22 °C). Evaluation: - After 3 days measurement of the thickness of the necrotic ring (corona) around the leaf hole. Comparison of the corona thickness of those of the example cultivars. Fungus culture: - On Agar-culture (3 % biomalt, 1,5 % agar) in Petri dishes at 20-22 °C in darkness. 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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