EFFECT OF GLYPHOSATE ON FUSARIUM HEAD BLIGHT IN WHEAT AND BARLEY UNDER DIFFERENT SOIL TILLAGES IN EASTERN CANADA

摘要

Fusarium head blight (FHB) is an important disease of wheat and barley, particularly in the wet conditions of eastern Canada. The principal pathogen associated with FHB, Fusarium graminearum, produces deoxynivalenol (DON), a mycotoxin that makes the grain unfit for food or feed. Surveys conducted in eastern Saskatchewan in 2005 and 2007 revealed that glyphosate application in the previous 18 months within minimum-till system was significantly associated with higher FHB levels in wheat and barley. This study aimed to determine the effect of glyphosate on FHB development in wheat and barley and on F. graminearum inoculum production under different soil tillages in eastern Canada. The experiment was performed during two years (2007-2008) at two different sites in Quebec, Canada (Saint-Augustin-de-Desmaures and Saint-Mathieu-de-Beloeil). Six trials were set in both sites, combining two cereal species, wheat and barley, and three soil tillages: moldboard plough, spring tillage (minimum-till) and directdrilling. For each trial, glyphosate or other herbicides chosen according to weed species were applied as main plot treatments on Roundup Ready~TM soybean the year preceding cereal crops. The next year, three wheat and three barley cultivars with a distinct FHB resistance level were sown in the main herbicide plots, constituting the subplots. In each main plot, two Petri plates containing a Fusarium-selective medium were placed facing the ground in order to capture spores coming from the soybean residues. FHB index, Fusarium-damaged kernels (FDK), deoxynivalenol (DON) content and F. graminearum inoculum production were measured. Glyphosate had no significant effect on FHB index, FDK or DON content, whatever the trial and the site. F. graminearum inoculum production was enhanced by glyphosate in only one trial out of twelve. The relationship between F. graminearum inoculum from soybean residues and DON content was weak. Therefore, it seems that glyphosate used on soybean the year preceding wheat or barley crop has no or low impact on FHB development and F. graminearum inoculum production under Quebec cropping conditions, whatever the tillage practices used.