Kaolin particle film limits grapevine downy mildew epidemic under open-field conditions and stimulates the plant defence response

Background and Aims Grapevine downy mildew, the most destructive grapevine disease caused by Plasmopara viticola, requires more environmentally friendly control measures. A chemically inert kaolin particle film (KPF) was tested for the control of downy mildew. Methods and Results Grapevines were pretreated with KPF before P. viticola infection under field conditions, then an epidemic was monitored for 2 years (2020 and 2021). A 6% KPF pretreatment significantly delayed the epidemic onset by 1-2 weeks and decreased the disease index by 30% compared to the untreated vines. The concentration of hydrogen peroxide and malondialdehyde in leaves was reduced by the KPF treatment, indicating mitigation of the oxidative damage caused by P. viticola infection. The protective effect of the application of KPF may be due to the increased activity of antioxidant enzymes and antioxidant metabolites. The activity of disease resistance enzymes and the expression of related genes were also increased by KPF treatment. Conclusions Kaolin particle film reduced grapevine downy mildew and reinforced the defence response of grapevines cultivated in the field. Significance of the Study The positive effect of KPF against downy mildew for grapevines in the field indicated that there is potential to develop KPF for the control of downy mildew.

Automated summary

The study found that kaolin particle film can reduce the occurrence of grapevine downy mildew and enhance the defense response of grapevines. This indicates the potential of developing KPF for the control of downy mildew.