Incidence of Heterobasidion irregulare aerial basidiospores at different locations in southern Quebec

摘要

Heterobasidion irregulare (Underw.) Garbel. amp; Otrosina is an important fungal parasitic basidiomycete of coniferous trees throughout temperate regions of the world. In Canada, the disease was first reported on red pine in Ontario in 1955, then in Quebec in 1989. As infection probability is proportional to the density of its aerial basidiospores infecting freshly cut pine stumps, the purpose of this study was to quantify the H. irregulare aerial basidiospore deposition along a southern Quebec transect. Spore counts from automated rotary arm collectors were determined by using a ribosomal ITS TaqMan real-time PCR detection assay. Total count was performed on rods at each location, with the highest score of 706.3 spores in Harrington, then 459.6 spores in Cowansville, rapidly decreasing to 52.3 spores in Compton and reaching lows in St-Aubert and Rimouski, with an eastward direction on the transect. Clearly, plantations in southwestern Quebec are at a higher risk of infection than anywhere else in the province. With few exceptions, weekly spore depositions at all sites other than Harrington were greatly below 0.2 per m(-2)h(-1). Despite this very low spore deposition rate observed in one season, the large number of trees thinned annually warrants that stump treatment with Rotstop (R) C is still the best strategy, especially in valuable plantations, to prevent against infection by Heterobasidion.