Root rot severity and fungal populations in spring common, durum and spelt wheat, and Kamut grown under organic management in western Canada

A 3-yr field study (2010 to 2012) was conducted in the Brown soil zone of southwest Saskatchewan to determine the reactions of common, durum and spelt wheat cultivars currently registered in western Canada, and of Kamut wheat, to common root rot (CRR) under organic management. The genotypes selected for this study are often grown by organic producers in this region. Over the 3 yr of this study, Cochliobolus sativus, the main causal agent of CRR, was the fungus most frequently isolated from discoloured subcrown internodes, followed by Fusarium spp. The latter constituted an overall total of over 19% of all isolations and consisted of at least 12 different species, the most frequently detected of which were F. equiseti, F. avenaceum, F. acuminatum and F. oxysporum. The relative prevalence of the most commonly isolated genera/species agrees most closely with previous studies conducted under organic management. In general, C. sativus was less common in Kamut than in durum and spelt wheat, and it was more frequently isolated from durum than common wheat. In contrast, there were few differences in the isolation of Fusarium spp. among wheat species. Their isolation was greater for common wheat and Kamut than for durum wheat. For all 3 yr, the greatest mean CRR severity was observed in spelt wheat, followed by durum wheat and Kamut, with common wheat having the lowest average severity. For individual cultivars, the durum wheat AC Avonlea, Kyle and Transcend had the greatest CRR severity of all cultivars in this species and CDC Verona the lowest. Common wheat cultivars AC Elsa, CDC Kernen and Red Fife had the greatest CRR severity and Superb and Unity the lowest severity within their species. Under organic conditions, avoiding growing cultivars with high susceptibility to CRR is recommended given the expected presence of this disease in most fields and environments.