Biological control of fusarium root rot and seedling blight of soybean in Ontario

Project Code BPI09-070

Project Lead

Allan Xue - Agriculture and Agri-Food Canada

Objective

To assess the efficacy of experimental formulations of Clonostachys rosea strain ACM941 for management of soybean Fusarium root rot and seedling blight in greenhouse and field trials

Summary of Results

Background

Fusarium root rot and seedling blight, caused by a Fusarium complex - which includes Fusarium solani, F. oxysporum, and F. graminearum - are top priority issues that affect soybean production in Canada according to stakeholder consultations held in 2006. Current management of these diseases relies on only a few fungicide seed treatments, thus the need to investigate new and reduced risk seed treatment options has been put forward. In previous studies, the biocontrol agent Clonostachys rosea strain ACM941 was identified as an antagonist against a number of soil-borne and seed-borne pathogens, including F. solani, F. oxysporum, and F. graminearum. ACM941 is identified as a mycoparasite and its hyphae can coil around and penetrate pathogen mycelia, resulting in reduced pathogen growth, loss of mycelial cytoplasm, and mycelial lysis in later stages.

Approaches

In 2009, efficacy of the formulated ACM941 was compared with the commercial standard treatment Vitaflo-280 (carbathiin + thiram) for the control of root rot caused by each pathogen (F. solani, F. oxysporum, and F. graminearum). Following an initial efficacy screening in greenhouse trials in Ottawa, ACM941 was evaluated in replicated field trials under inoculated conditions. Each Fusarium species was tested in two soybean production regions in Ontario: Harrow in south-western Ontario (long-season soybean) and Ottawa (short-season soybean). The population dynamics of the biocontrol agent were also monitored in the rhizosphere of soybean plants grown from ACM941-treated soybean seeds in both greenhouse and field environments.

Results

In 2009, appropriate root rot pressure in greenhouse trials was developed by spraying Fusarium suspension. When compared to the untreated control, neither ACM941 nor Vitaflo-280 showed significantly improving emergence or reducing root rot severity in greenhouse trials. Root rot caused by all three Fusarium species developed in the Ottawa experimental field at levels sufficient for efficacy testing; however, only slight root rot was observed in the Harrow field trials, even under the artificially inoculated conditions. In field plots inoculated with F. graminearum, ACM941 significantly increased emergence by approximately 15% at two sites, but showed no effect on disease severity or yield compared to the untreated control. In F. oxysporum inoculated plots, ACM941 significantly increased emergence by 14.6% and yield by 6.0%, and reduced root rot severity by 75.0% in Harrow, but showed no significant effect in Ottawa. In soybean inoculated with F. solani, ACM941 significantly reduced root rot severity by 76.9% in Harrow and showed significant effects on emergence and yield at both sites. The success of ACM941 in increasing emergence and yield and reducing root rot severity was numerically better, but the results were not significantly different from those of Vitaflo-280 in these trials. The population dynamics of ACM941 bioagent, after the seed treatment application, were monitored in both greenhouse and field environments. In the greenhouse the density of ACM941 increased with soybean root growth, and maximum density occurred between 15 and 35 days after planting. In the field environment, the density of ACM941 was at its highest level in late September, when plants were at the stage of early maturity. The results of this project suggest that ACM941 is better than, or at least as effective as, the common seed treatment fungicide Vitaflo-280 for controlling Fusarium root rot in soybean. However, reliability of these results should be confirmed through additional studies as less than satisfactory disease pressure was observed in this project, even though artificial inoculation was applied. Further trials are being conducted in a combined project (BPI10-020), which involves the control of FHB in wheat, in Ottawa and Harrow in 2010 to confirm ACM941 efficacy for the control of soybean root rot and population dynamics in the soybean rhizosphere over an extended period of time through the previous winter season.

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