Pathways to false-positive diagnoses using molecular genetic detection methods; Phytophthora cinnamomi a case study.

Area of Science:

• Plant Pathology
• Molecular Diagnostics
• Microbial Genetics

Background:

• Phytophthora cinnamomi is a highly invasive plant pathogen impacting diverse ecosystems.
• Accurate detection of P. cinnamomi is crucial for managing its spread in plants and environments.
• Previous studies developed species-specific primers for P. cinnamomi detection using PCR methods.

Purpose of the Study:

• To evaluate the specificity of existing P. cinnamomi-specific primer sets.
• To assess primer performance against closely related Phytophthora species within clade 7.

Main Methods:

• Tested eight previously reported P. cinnamomi-specific primer sets.
• Evaluated primer specificity against eleven other Phytophthora species from clade 7.
• Utilized polymerase chain reaction (PCR) techniques for specificity assessment.

Main Results:

• Only three out of the eight tested primer sets demonstrated specificity to P. cinnamomi.
• Several primer sets cross-reacted with closely related Phytophthora species within the same clade.
• Specificity was not consistently confirmed when tested against phylogenetically similar species.

Conclusions:

• The study underscores the critical importance of rigorous testing against closely related species for validating microbial diagnostic primers.
• Many existing P. cinnamomi-specific primers may lead to inaccurate diagnoses due to lack of specificity within clade 7.
• Findings are relevant for improving species-specific diagnostic methods across various microbial fields.