A biomarker for the identification of four Phaeoacremonium species using the beta-tubulin gene as the target sequence.

A real-time polymerase chain reaction (PCR) was developed for the rapid detection and identification of Phaeoacremonium species, the fungi associated with severe diseases in grapevines. A degenerate primer pair (F2bt-R1bt) with homology to the beta-tubulin gene was designed to be used in the amplification of 11 species of Phaeoacremonium. Four species-specific probes labelled with three different fluorescent dyes were designed to be used with the degenerate primers in a real-time PCR for the identification of Phaeoacremonium aleophilum, P. parasiticum, P. viticola and P. mortoniae. Combinations of two probes in a duplex real-time PCR allowed to detect and identify a mixture of Phaeoacremonium species and cross-amplifications were not detected. This method was applied to detect Phaeoacremonium species in eight wood fragments from grapevine plants naturally infected, and results were compared with those obtained with nested PCR and culturing on growth media. Real-time PCR detected Phaeoacremonium in 100% of the analysed fragments, whereas nested PCR did only in the 62% of them and requiring subsequent restriction fragment-length polymorphism analysis to identify the species. This method is a sensitive tool to detect and identify Phaeoacremonium species in infected grapevine wood. Real-time PCR assay defined here can be used in a plant nursery program to identify pathogen-free plants in order to manage Petri disease of grapevines.