ID/Diagnostic: Morphological
Morphological: Most frequently isolated on malt extract agar (supplemented with streptomycin sulfate) from the leading edge of discolored wood and necrotic leaf petioles, but rarely from necrotic bark.
Kowalski (2006) notes that C. fraxinea differs from other species of Chalara by its small, short, cylindrical phialoconidia extruded in chains or in slimy droplets, morphological features of the phialophores, and by colony characteristics.
In Progress / Literature-based Diagnostics:
Molecular: Bakys et al. (2009) combined PCR amplification of the ITS region of the ribosomal genes with terminal restriction fragment length polymorphism (T-RFLP) to determine which pathogens existed on Fraxinus excelsior in Sweden. In order to identify taxa in the T-RFLP profiles, PCR products were cloned, enabling sequencing of the ITS region of the rDNA genes for individual taxa within the mixed sample, and subsequent identification by database comparison.
Johansson et al. (2010) developed a set of species-specific PCR primers, based on ITS sequences, to detect C. fraxinea in plant (Fraxinus excelsior) tissue.
Real-time PCR: Ioos et al. (2009) developed a real-time PCR for detection of C. fraxinea in planta . Species-specific polymorphisms observed within the ITS region were used to design a primer pair and a dual-labeled probe for use in a real-time PCR assay for the detection of C. fraxinea. In silico and in vitro assessments showed that the PCR could detect as little as 20 fg of C. fraxinea DNA.
Chandelier et al. (2010) developed a real-time PCR for the detection of C. fraxinea from woody tissues. A procedure for DNA extraction from woody tissues using an electric drill yielded DNA of appropriate quality for DNA extraction. PCR primers and Taqman probes were developed based on the internal transcribed spacer (ITS) region of a multi-copy gene rDNA. The primers amplified an 81 bp fragment from C. fraxinea. The limit of detection was 5 pg of genomic DNA per PCR.