Varietal Resistance of Grape to the Powdery Mildew Fungus, Uncinula Necator

Abstract

Powdery mildew of grapevines, caused by Uncinula necator,is considered to be a major disease worldwide. The fungus utilizes haustoria to withdraw nutrients from epidermal cells and spreads rapidly under favorable conditions. Commercial grapes originating from Vitisspecies are the most desirable varieties for commercial production but are usually most susceptible to powdery mildew. Muscadiniaspecies possess disease resistant characteristics but poor fruit traits. The development of resistant germplasm has involved many countries and as a result, screening procedures are varied and utilize numerous evaluation criteria. Published studies on varietal resistance or relative susceptibility suffer from inconsistencies in terminology and approach. Further research to develop germplasm with standardized levels of susceptibility will benefit the grape industry. A list of cultivars and their relative susceptibilities to powdery mildew is compiled.