Fusarium populations in roots of oilseed and pulse crops grown in eastern Saskatchewan

Abstract

Roots of canola, flax, lentil and pea crops, commonly grown in rotation with wheat and barley on the Canadian Prairies, were sampled for extent of discolouration and associated fungal populations in eastern Saskatchewan, in 2000 and 2001. Fusarium was the genus most commonly isolated from pulse crops, particularly lentil, and one of the most common genera isolated from oilseed crops. The discolouration severity of pulse and flax roots was associated with Fusarium spp., and that of canola with Alternaria spp. Cochliobolus sativus and other commonly isolated species appeared to be present in roots as weak pathogens or saprophytes. Most of the Fusarium spp. have also been isolated from cereal crops affected by crown/root rot or fusarium head blight (FHB) in the province, although at different relative levels. These included F. avenaceum, the most commonly isolated species, and F. culmorum and F. graminearum, which were among the least prevalent species. This is the first report of isolation of F. graminearum from roots of field-grown pulse and oilseed crops in western Canada. For most crops, the number of tillage operations in the previous 3 yr was positively associated with the occurrence of C. sativus and negatively associated with that of F. avenaceum. Our results suggest that the noncereal crops examined would help to maintain or increase Fusarium inoculum in plant tissue, which might contribute to the development of crown/root rot and FHB in subsequently grown cereal crops, especially under conditions more conducive to disease development. This would especially be the case for pulse crops, which had the highest levels of root discolouration, and F. avenaceum. However, noncereal crops would not be significant reservoirs of inoculum of F. culmorum or F. graminearum. Key words: Fusarium avenaceum, Fusarium graminearum, Fusarium head blight, oilseed, pulse, cereal, tillage, crop rotation