Detection and quantification of Phytophthora species which are associated with root-rot diseases in European deciduous forests by species-specific polymerase chain reaction.
Oligonucleotide primers were developed for the polymerase chain reaction (PCR)-based detection of selected Phytophthora species which are known to cause root-rot diseases in European forest trees. The primer pair CITR1/CITR2, complementing both internal transcribed spacer regions of the ribosomal RNA genes, gave a 711 bp amplicon with Phytophthora citricola. The Phytophthora cambivora specific primer pair CAMB3/CAMB4 (producing a 1105 bp amplicon), and the Phytophthora quercina specific primer pair QUERC1/QUERC2 (producing a 842 bp amplicon) were derived from randomly amplified polymorphic DNA (RAPD)-fragments. All 3 primer pairs revealed no undesirable cross-reaction with a diverse test collection of isolates including other Phytophthora species, Pythium, Xerocomus, Hebeloma, Russula and Armillaria. Under the PCR conditions described the detection of an amplicon was possible down to 100 pg (Phytophthora cambivora), 4 pg (Phytophthora quercina) and 2 pg (Phytophthora citricola) target DNA. This diagnostic PCR system was able to detect Phytophthora citricola, Phytophthora quercina, and Phytophthora cambivora in seedlings of pedunculate oak (Quercus robur) and European beech (Fagus sylvatica) which were artificially infected under controlled conditions.