Efficacy evaluation of the formulated biocontrol agent, Clonostachys rosea strain ACM941 for the management of Fusarium Head blight in wheat

Project Code BPI09-040

Project Lead

Dr. Allen Xue - Agriculture and Agri-Food Canada

Objective

To evaluate the efficacy of Clonostachys rosea strain ACM941 and generate data for its registration as management tool for Fusarium Head Blight in wheat

Summary of Results

Background

Fusarium head blight (FHB), caused by Gibberella zeae (syn. Fusarium graminearum), is the most significant disease in wheat. This disease has been identified as a priority issue in wheat by stakeholders in Canada in 2006. It is responsible for over $1 billion in losses in agricultural industries in Canada and the United States. Infection of wheat by the pathogen results in the reduction of grain yield and quality, as well as kernel contamination (with deoxynivalenol (DON) and other mycotoxins). Current management of this disease is reliant on fungicides to sustain the productivity and quality of grains in most wheat production areas. Multiple fungicide applications have led to an increase in: the economic cost to growers, public concerns regarding pesticide risks, and the risk of pathogen resistance to fungicides. Therefore, it is important to develop alternatives to conventional methods to help manage pesticide risks and resistance. AAC has patented a strain of fungus discovered by Dr. A. G. Xue, Clonostachysrosea, ACM941, which is very effective at fighting against many plant pathogens, including F. graminearum. Previous research, including Pesticide Risk Reduction (PRR) Program projects BPI07-110 and BPI08-020, showed that strain ACM941 can effectively reduce FHB incidence and mycotoxin levels in wheat grain. 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

Evaluation of the efficacy of the formulated product, ACM941-CL01 for FHB control was conducted by Dr. Xue under both greenhouse and field conditions at the Central Experimental Farm (CEF), Ottawa, Ontario from 2007 to 2009 under projects BPI07-110, BPI08-020, and the current project. To determine the effective concentration range, five concentrations ranging from 104 to 108 cfu/ml were used in both greenhouse and field tests. These were compared to untreated controls and to the commercial standard fungicide Folicur 432F (active ingredient tebuconazole). Efficacy evaluation also included a spray experiment in which ACM941-CL01 and Folicur 432F were alternated to evaluate efficacy when fewer sprays of Folicur 432F were used. The concentration 107 cfu/ml was used for evaluating the effects of cultivar resistance on the efficacy of ACM941-CL01 on nine cultivars in 2007 and on three cultivars in 2009. In both greenhouse and field tests, plants were inoculated with F. graminearum macrospore suspensions or Fusarium infested wheat grain to establish disease pressure. ACM 941-CL01 was then applied by spraying the treatment on wheat heads at the 50% blossom stage. Efficacy was evaluated by examining the area under the disease progress curve (AUDPC), the percentage of infected spikelets (IS), the percentage of Fusarium damaged kernels (FDK), the 1000-kernel weight (TKW), yield, and the amount of DON in wheat kernels. To evaluate the efficacy of ACM941 for the suppression of perithecial formation, ACM941 was sprayed on corn kernels at 5 ×104 cfu/ml in 2007 and 2008 and on crop residue stems of corn, soybean, and wheat in 2009, either on the same day or 3 days prior to treatment with the Fusarium pathogen.

Results

Sufficient disease pressure was obtained in both greenhouse and field tests for the evaluation of the efficacy of five ACM941-CL01 concentrations to control FHB to proceed. All the concentration treatments ranging from 104 to 108 cfu/ml provided significant levels of reduction in the four disease parameters AUDPC, IS, FDK, and DON under both greenhouse and field conditions. Better efficacy was observed with increases in the conidial concentration. The treatments at 108 cfu/ml provided the best efficacy, reducing AUDPC by 43%, IS by 45%, FDK by 43%, and DON by 28% and increasing yield by 7% in the field tests, compared to untreated controls. In general, treatment with ACM941-CL01 did not significantly differ from the Folicur fungicide in these parameters. Enhanced effectiveness was not observed when ACM941 was sprayed with 50% Folicur 432F, compared to the application of 50% Folicur alone. ACM941 showed consistent efficacy in controlling FHB on different cultivars, although the different genotypes expressed different levels of resistance to F. graminearum. On average, in 6 field trials in 9 cultivars, ACM941-CL01 significantly reduced AUDPC by 20 to 24%, IS by 24%,and FDK by 11 to 34.8%. Two trials demonstrated a significant reduction in DON by 13.9 to 18.6%. ACM941-CL01 significantly inhibited perithecial formation on kernels and all three types of crop residues. On average, ACM941 reduced the daily production of perithecia by 59 to 68% on corn kernels, 90% on corn residue, 90% on soybean residue, and 71% on wheat residue.

Results of this research project suggest that ACM941-CL01 is an effective biocontrol product that can be used as a foliar application at concentrations of 107 to 10 8 cfu/ml for the control of FHB , or used as a spray treatment for crop residues to inhibit G. zeae perithecial production, thus reducing the initial inoculum of FHB . It is anticipated that the bioagent may be used as an alternative to fungicides or incorporated as a part of an integrated disease management system for a pesticide risk reduction strategy. The use of this product would greatly reduce the application of conventional fungicides, reducing risks associated with their use, including risk of resistance development in the pathogen population. Due to the significance of this disease and the promising data from this work, grower representatives selected ACM941-CL01 as a Pest Management Centre priority for biopesticides regulatory support at the PRR program’s first Biopesticides Selection Meeting in March 2010. Further work is planned to validate efficacy results in diverse environments and confirm perithecial reduction over an extended time period after applied on plant residues. Meanwhile the PRR Biopesticides Regulatory Support team, together with the Health Canada’s Pest Management Regulatory Agency, Dr. Xue, and the commercial partner ICUS, are working toward the first time registration of this promising product in Canada and the USA. For further information contact Dr. Allen Xue.

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