Rotation and fertility effects on root rot of spring wheat in southwest Saskatchewan

Abstract

Spring wheat grown in a replicated trial for one or two years after summerfallow, lentil, flax, or continuously (with and without fertilizer N) was examined for subcrown internode discoloration from 2000 to 2002 in southwest Saskatchewan. Discolored tissue was plated on nutrient agar for fungal identification. Root rot was in general present at highest levels in wheat grown after lentil, and at lowest levels in wheat grown continuously with low N fertility. The most common species were Cochliobolus sativus and Fusarium spp. Among the latter, F. avenaceum, F. equiseti and F. pseudograminearum were the most commonly isolated. F. avenaceum is the most important fusarium head blight (FHB) pathogen in western Saskatchewan. The percent isolation of Fusarium species was lowest in continuously-grown wheat with low N. Wheat after lentil had one of the highest levels of F. avenaceum. Among the crop rotations examined, it appears that the most favourable to the development of root rot in spring wheat was a wheat-lentil rotation. This rotation may also contribute to the build-up of F. avenaceum inoculum for the development of FHB, which is an important emerging disease of wheat and barley in western Saskatchewan.