Biostimulant and fungicidal effects of phosphite assessed by GC-TOF-MS analysis of potato leaf metabolome

Phosphite (Phi), an analog of phosphate, is increasingly used worldwide as fungicide, fertilizer and plant biostimulant. Studies using various plant systems provided insights on how Phi is translocated in plants and on its mode of action against pathogens. However, little evidence is present at the metabolite level, of the compounds present in plants that are responsible in the enhanced resistance to pathogens. As Phi is used to control late blight, the most devastating disease of potato, caused by the oomycete Phytophthora infestans, this study used potato as a model plant to study the effects of this chemical. Analysis of potato leaf metabolome, using GC-TOF-MS, revealed that several metabolite pools are modified by Phi applications. Phi treatments were found to be associated with higher levels of components of the phenylpropanoid pathway such as chlorogenic acid, caffeic acid and salicylic acid, compounds that are known to be essential components of plant defense response to biotic and abiotic stresses, providing therefore additional support to an effective indirect mode of action.