A new real-time PCR assay to detect Chalara fraxinea
A real-time PCR assay has been developed to detect Chalara fraxinea (EPPO Alert List) directly in plant tissue. This new assay was found to be more efficient than isolation on agar plates. Isolation of C. fraxinea is particularly difficult and time-consuming because of its poor growth on artificial growing media (C. fraxinea is easily outcompeted by faster growing fungi). This real-time PCR assay successfully detected the presence of C. fraxinea in 28 out of 33 ash samples displaying typical dieback symptoms, either in sapwood or in necrotic inner and outer bark; whereas pure cultures of C. fraxinea could only be obtained from 12 of the 33 samples. The specificity of real-time PCR was also successfully checked with a collection of European fungal species, either phylogenetically close to C. fraxinea or sharing the same ecological niche. It is considered that this new real-time PCR assay will be a useful tool for both monitoring programmes and research on the epidemiology of ash dieback.
Sources
Ioos R, Kowalski T, Husson C, Holdenrieder O (2009) Rapid in planta detection of Chalara fraxinea by a real-time PCR assay using a dual-labelled probe. European Journal of Plant Pathology (in press).