A phytocomplex obtained from a Salvia officinalis cell culture effectively controls the grapevine downy mildew pathogen Plasmopara viticola

The impact of conventional fungicides on environmental and human health has increased the interest in safer alternatives such as plant secondary metabolites, generally having a better toxicological profile. However, plant genetics, agronomic practices, climatic conditions and extraction methods strongly affect the quality and quantity of secondary metabolites obtained from field grown plants. These factors cause limitations to the standardization needed for industrial production. Plant cell culture technology can meet this need: totipotent cells grown in controlled conditions can provide a highly homogeneous biomass with specific chemical characteristics. A phytocomplex, with standardized rosmarinic acid content, was obtained from a selected cell line of Salvia officinalis. The Salvia officinalis phytocomplex (SOP) was tested against the grapevine downy mildew pathogen, Plasmopara viticola. Grapevine leaf disks were sprayed with SOP and with fresh P. viticola sporangia. Sporulation level on each disk was assessed after 7 days with an image processing software. SOP at 5 g/l reduced by 95% the sporulation level compared to the control treatment. SOP was significantly more effective than rosmarinic acid alone, tested at the concentration found in SOP. Persistence of the phytocomplex was also assessed: leaves were sprayed with SOP and, after a few days, they were detached and inoculated. SOP applied 5 days before inoculation reduced by 90% the sporulation level compared to the control. These results highlight the possibility for plant protection industry to take advantage of cell culture techniques to produce safer pesticides with high quality standards.