Role of chitosan against grapevine downy mildew

Abstract

The study of environmentally friendly active principles against downy mildew represents one of the main challenges in viticulture. In this context, the aim of the present trial was to investigate the efficacy of chitosan as a resistance elicitor against downy mildew and to study the metabolites involved in the interaction plant-chitosan-pathogen by a metabolomics approach. The experiments were carried out on potted vines of Merlot R18 grafted on SO4 rootstock, Guyot trained, during 2022. Leaf disks pre-treated with chitosan were infected by Plasmopara viticola sporangia in 3 phenological phases and the development of infection was recorded. The most significant findings were: 1) Chitosan resulted as an effective elicitor of defense mechanism against Plasmopara viticola. 2) The elicitor activity of chitosan was explained mainly through the induction of some secondary metabolites (terpenes and resveratrol), fatty acids (involved in the biosynthesis of sterols), and hormones (brassinosteroids and abscisic acid). 3) The best efficacy corresponded to the application of chitosan 48 hours before the infection. The timing of the treatment was, therefore, one of the key factors for the success of chitosan treatment.