| Summary: | Specialization: Plant Science Degree: Master of Science Abstract: Fusarium root rot is a major disease of soybean (Glycine max) in many regions worldwide. As soybean is a relatively new crop in Alberta, Canada, studies were undertaken to determine the occurrence and severity of root rot in this province, identify and characterize the Fusarium species associated with disease development, and evaluate seed treatments and host resistance as disease management tools. Root rot was found in all soybean crops surveyed in 2013 and 2014. A total of seven species of Fusarium were identified from infected roots based on their morphological characteristics, with Fusarium avenaceum, F. solani, F. oxysporum, and F. acuminatum occurring most frequently. In greenhouse bioassays, isolates of F. proliferatum and F. acuminatum were the most aggressive, although some isolates of F. acuminatum caused little disease. Seed treatment with ipconazole + metalaxyl + fludioxonil, ipconazole + metalaxyl, fludioxonil + metalaxyl, or penflufen + prothioconazole + metalaxyl resulted in relatively high crop emergence rates (≥70%) under field conditions, while in greenhouse experiments, ipconazole + metalaxyl and carbathiin + thiram provided the best results. The resistance of soybean genotypes to F. avenaceum varied significantly, with genotype 90M01 having the highest emergence rate (83%) under field conditions. In greenhouse trials, the genotype Tundra was most resistant to root rot, whereas TH29002RR was the most susceptible. The results suggest that while root rot represents a significant challenge to soybean production in Alberta, fungicidal seed treatments and planting of genotypes with improved resistance may help to mitigate the impact of this disease.
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