Chitosan application reduces downy mildew severity on grapevine leaves by positively affecting gene expression pattern

Abstract

Grapevine (Vitis vinifera) is one of the most economically relevant crops in the world, producing more than sixty million tonnes a year. Unfortunately, almost all cultivars currently used for grape or wine production are sensitive to various pathogens, such as the oomycete causal agent of downy mildew, Plasmopara viticola, so that, generally, up to 15 fungicide treatments are needed to prevent diseases on leaves and berries. Nevertheless, fungicides have many different problems in terms of their impact on the environment and human health. To this end, some new chemicals have been used in the recent years. These are bio-stimulants and defence inducers, which are mainly used in the organic agriculture. Previous research has led to different results regarding their effectiveness, especially in the field. In 2020, an experimental product (chitosan - (C6H11O4N)n), capable of inducing defence mechanisms against downy mildew in grapevine, was tested in vineyard. Our study clearly showed that disease severity on canopy was reduced by 30%, on average, in the chitosan-treated grapevines in field and that several genes, encoding for proteins and enzymes of key defence-related metabolic pathways are up-regulated upon treatment.