EVALUATION OF A SEAWEED EXTRACT OF RUGULOPTERYX OKAMURAE AGAINST ERYSIPHE NECATOR IN GRAPEVINE

Abstract

Powdery mildew, caused by Erysiphe necator, is a widespread disease that causes high economical losses in viticulture. The main strategy to control the disease is the recurrent application of sulphur based phytochemical compounds. However, in order to reduce their accumulation in the environment and promote the sustainability of the sector, the European Commission has applied restrictions to the number of pesticide treatments and the maximum quantity of fungicides to be applied in viticulture. Seaweeds, in particular macroalgae, are marine resources rich in sulphated polysaccharides with bio-protective potential for the plant, representing an environmentally-friendly alternative approach for sustainable wine production.

In the current work we investigated the antifungal efficacy of the brown invasive macroalgae Rugulopteryx okamurae against Erysiphe necator. Rugulopteryx was collected from Algeciras coast (South Spain) and an aqueous extract was developed using a water /ethanol extraction protocol. A foliar spraying (6 gr/L) of Rugulopteryx okamurae extract was applied to Tempranillo and Cabernet Sauvignon plants grown in a green-house facility and the antifungal activity of the extract was tested by monitoring disease symptoms after fungi infection. Results showed that while the incidence of powdery mildew was similar in treated than in control plants (water treated), the disease severity was 1.7 fold lower for treated plants in comparison to controls. Further research by exploring grapevine resistance/defence mechanisms is necessary to explain this extract´s mode of action.

Evidencing the efficacy of Rugulopteryx okamurae as a biostimulant/fungicide is a finding of major importance, as it would be a first step towards its inclusion in a circular scheme, reducing its accumulation on the coast and at the same time benefiting the wine sector.