GC-MS metabolite profiling of Phytophthora infestans resistant to metalaxyl

Phytophthora infestansis the most important potato pathogen worldwide. Various alternatives have been used to control the pathogen, including continuous applications of phenylamide fungicideswhich has caused a rapid development of resistance in populations of P. infestans. Despite the importance of the disease, metabolite profiling of fungicide-resistant P. infestans has not been reported. In vitro resistance of Phytophthora infestansisolates to metalaxylwas characterized and metabolic changes in resistant isolates were evaluated at low (0.5 mg/L) and high (100 mg/L) concentrations of the fungicide. About 70% of the isolates tested showed resistance to metalaxyland a total of 49 metabolites were differently expressed in resistant isolates growing in the presence of the fungicide. Principal components analysis revealed a distinct metabolite profile of resistant isolates exposed to both low and high levels of metalaxyl. The main metabolites responsible for the clustering in both fungicideconcentrations included fatty acids such as hexadecanoic and octadecanoic acids, sugars such as glucose and fructose, aminoacids such as proline and valine, and organic acids such as butanedioic and propanoic acids. Potential resistance-related metabolic pathwaysare mostly involved in the regulation of the pathogen’s membrane fluidityand included the fatty acid biosynthesis as well as the glycerophospholipid metabolismpathways. This is the first metabolomic-based characterization of fungicideresistance in plant pathogens.