Fusarium species affecting field pea, dry bean and soybean in Manitoba

Fusarium root rot of field pea, dry bean and soybean is a concern in Manitoba. In recent years, there has been an increasing number of reports of severe losses in plant stand and yield caused by root rot. Annual surveys of dry bean, field pea and soybean have been conducted to determine the prevalence and severity of root rot, to identify the common root pathogens and to detect the presence of any new root diseases. These annual surveys date back over 10 years for dry bean and field pea, but as soybean is a relatively new crop to Manitoba, the annual soybean root disease surveys began in 2012. Since 2014, approximately 40 crops each of pea, bean and soybean were sampled per year where roots were rated for the incidence and severity of root rot disease and fungal species were identified. The isolation and identification of fungal species was based on morphology and analyses of the IGS and ITS regions and the EF1-α gene. Our research has shown that root rot of pea, bean and soybean in Manitoba is primarily caused by several species of Fusarium. Fusarium species isolated in each year included F. oxysporum, F. graminearum, F. redolens, F. acuminatum, F. avenaceum, and F. solani, with some Fusarium spp. common to all three crops. A Fusarium species of concern is F. graminearum which is the main causal agent of Fusarium Head Blight (FHB) in cereals. FHB is considered to be the most serious disease affecting cereals causing significant yield losses worldwide. An important finding from our research was the identification of F. graminearum in dry bean and soybean. With increasing acreages of these crops in Manitoba, F. graminearum may be problematic in current crop rotation regimes with cross-pathogenicity and source of inoculum issues. Overall, findings from our research will support the development of effective management strategies for root rot disease associated with different Fusarium spp. affecting field pea, dry bean and soybean in Manitoba and across Canada.