Identification et analyse de marqueurs génétiques diagnostiques de deux champignons de rouille des pins durs (Cronartium comptoniae et Peridermium harknessii) et identification d'un hyperparasite de ces rouilles au Québec

Fungi responsible for rust of two-needle pines cause serious problems in the province of Québec because of their negative actions on tree growth and thus on the economic value of our forest. The development of molecular diagnostic tools for these pathogens should help us, in the future, to detect infected seedlings before symptoms become visible. This will help to avoid the sending of infected seedlings on the field and thus the propagation of rust pathogens. Two species of rust fungi are described in this study, the autoecious rust Peridermium harknessii and the heteroecious rust Cronartium comptoniae. Molecular markers diagnostic for each species were developed with the ribosomal DNA region ITS 1 and the coding gene of Actin. In the course of this investigation on rust DNA, another fungus was isolated and described since its DNA was found in several samples. This fungus, Cladosporium tenuissimum, is a hyperparasite of rust fungi and is described for the first time associated with rust fungi in North America.