Foliar selenium application reduces late blight severity and incidence and induces the phenolic pools in potato leaves and tubers

Potato is the 4th most consumed food crop worldwide and is central to global food security. However, potato production faces many constraints including poor yield and quality, diseases, and pest pressure. Among potato diseases, late blight is one of the most devastating pathogens causing a serious threat to potato production. Whereas disease control by fungicides appears to be effective in conventional production systems, organic systems are still looking for viable disease control options. Selenium is a mineral micronutrient essential to humans and animals in trace amounts, and is widely used for crop and livestock biofortification. Nonetheless, its essential role for plant growth is not yet well-established, despite its role as antioxidant, in delayed senescence and protection against fungal infection and aphid feeding. As an alternative to chemical fungicides, pesticides derived from certain minerals such as silicon and selenium may be options for organic production. To date however, the role of selenium on potato late blight is unknown. This study was designed to evaluate the effect of selenium on late blight in potato plants grown in greenhouse, and to determine some of its modes of action in the plants. Our preliminary results show that foliar selenium applications reduce the severity and incidence of late blight and interfere with the phenylpropanoid pathway, inducing the production of secondary metabolites including anthocyanins and hydroxyl-cinnamic acids in the leaves and tubers of treated plants compared to non-treated plants. These results suggest that selenium may contribute to improved potato late blight control.