Evaluation of Molecular Markers for Phytophthora ramorum Detection and Identification: Testing for Specificity Using a Standardized Library of Isolates

ABSTRACT Given the importance of Phytophthora ramorum from a regulatory standpoint, it is imperative that molecular markers for pathogen detection are fully tested to evaluate their specificity in detection of the pathogen. In an effort to evaluate 11 reported diagnostic techniques, we assembled a standardized DNA library using accessions from the World Phytophthora Genetic Resource Collection for 315 isolates representing 60 described Phytophthora spp. as well as 11 taxonomically unclassified isolates. These were sent blind to collaborators in seven laboratories to evaluate published diagnostic procedures using conventional (based on internal transcribed spacer [ITS] and cytochrome oxidase gene [cox]1 and 2 spacer regions) and real-time polymerase chain reaction (based on ITS and cox1 and 2 spacer regions as well as β-tubulin and elicitin genes). Single-strand conformation polymorphism (SSCP) analysis using an automated sequencer for data collection was also evaluated for identification of all species te...