Efficient multiplex simple sequence repeat genotyping of the oomycete plant pathogen Phytophthora infestans

► A one-step multiplex PCR method employing 12 SSR markers was developed for fast genotyping of Phytophthora infestans. ► This one-step multiplex PCR method resolved distinct multilocus genotypes (MLGs) of isolates around the globe. ► Standardization with guidelines and reference material allowed unambiguous scoring of more than 5000 isolates. ► The methods presented allow the analysis of datasets comprising isolates of mixed ploidy levels in P. infestans. ► Two methods were developed for direct P. infestans genotyping from infected leaves and stored infected leaf extracts.