“Edible coatings”: Application of natural berry waxes to protect grapes against Botrytis and powdery mildew infection

PROJECT TITLE: “Edible coatings”: Application of natural berry waxes to protect grapes against Botrytis and powdery mildew infection

Project leader:  Drs Justin Lashbrooke & Philip Young

Duration: 1 January 2022 – 31 December 2024

Project Summary:

Botrytis and Erysiphe necator (powdery mildew) infection of grape berries has the potential to cause significant crop and financial losses for growers. Breeding for Botrytis resistance has proven to be challenging due to the absence of resistance genes while breeding for mildew resistance involves crossing with non-vinifera cultivars potentially compromising quality. Therefore, application of fungicide treatments is required, but as powdery mildew and Botrytis regularly infect late in berry development, applications are regulated, not always successful, and generally not environmentally friendly. This project will investigate the development of environmentally friendly powdery mildew and Botrytis control agents, exploiting the antifungal properties of the naturally occurring berry surface waxes. Fruit surface waxes from several plant species, including grapevine, have been found to possess a wide range of bioactive antifungal properties. The wax covering a grape berry (or any other part of a plant) is extremely diverse and typically composed of over twenty different individual wax-type compounds (such as fatty acids, alkane, triterpenoids, and alcohols). Only some of these compounds possess antifungal properties, therefore understanding which specific waxes (or combination thereof) show antifungal activity is a primary focus of this work. Once we have determined which compounds from the wax layer are candidates to be used as a natural fungicide, methods for natural wax extraction and application to bunches will be optimised, and effects on berry physiology quantified. The potential to generate an environmentally friendly and non-toxic fungicide that may be applied close to harvest and even on post-harvest berries is an exciting potential result from this work. We have at our disposal a grapevine population of which shows a variety of wax compositions as well as susceptibility/resistance to powdery mildew and Botrytis infection. We have previously established methods for mildew and Botrytis infection scoring in grape berries and berry surface wax quantification.