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, as well as the Phytophthora quercina specific primer pair QUERC1/QUERC2, producing a 842 bq amplicon, were derived from randomly amplified polymorphic DNA (RAPD)-fragments presented In this paper. All three 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 a well discernable amplicon was possible down to 100 pg (P. cambivora), 4 pg (P. quercina), and 2 pg (P. citricola) target DNA. This diagnostic PCR system was able to detect P. citricola, P, quercina, and P. cambivora in seedlings of pendunculate oak (Quercus robur) and European beech (Fagus sylvatica) which were artificially infected under controlled conditions.