Development and evaluation of Paenibacillus polymyxa PKPB1 as a biofungicide for greenhouse cucumbers and peppers

Code de projet BPI06-090

Project Lead

Prem Kharbanda - Alberta Research Council

Objective

To evaluate the efficacy of a biocontrol agent in controlling diseases (Fusarium root and stem rots, powdery mildew, Pythium root rot and gummy stem blight) in greenhouse grown cucumbers and peppers

Summary of Results

Canadian greenhouse vegetable producers spend more than $3000 per acre for fungicides to control a number of serious diseases. The bacterium Paenibacillus polymyxa PKPB1, discovered by researchers at the Alberta Research Council, was developed and assessed as an alternative, biopesticide solution to help reduce reliance on conventional fungicides and slow the development of resistance to these chemicals within pathogen populations.

Efficacy

Over the course of this two year project, PKPB1 was evaluated as a biocontrol for fungal diseases of vegetable crops in a greenhouse hydroponic system. Trials to assess efficacy against Fusarium, Pythium, powdery mildew and gummy stem blight pathogens in greenhouse cucumber and pepper production were conducted at Alberta Research Council commercial-scale greenhouse facilities.

Three experiments were conducted to evaluate PKPB1 for Pythium control on cucumber. It was found that PKPB1 delayed development of Pythium root rot in the first two weeks after inoculation, showed similar effect at the end of six weeks after treatments were applied, indicating that PKPBI was as effective as a commercial product (Mycostop®) in suppression of root disease.

Two experiments were conducted on powdery mildew control on cucumber. Foliar application of PKPB1 spore suspension reduced the severity of powdery mildew on cucumber plants infected under natural conditions but the effect was not significant compare to the mildew on non-treated control. Also, foliar application of PKPB1 spore suspension did not significantly reduce the severity of gummy stem blight on cucumber plants and did not reduce infection caused by Fusarium solani on pepper fruits based on the data from the three sets of experiments. PKPB1 treatments were not seen to be phytotoxic in any of the experiments.

Production and characterization

Paenibacillus polymyxa PKPB1 spores were produced at 10L scale-up quantity and this was assessed for quality control and long-term storage. For all samples out of eight fermentation lots, levels of contaminants were below detectable limits and only the PKPB1 inoculum was present in the culture. Storage tests completed showed good viability of PKPB1 spores after storage for 1, 3, 6 and 12 months at room temperature.

Production of entorotoxins was determined by detecting presence of DNA sequences encoding hemolysin (HBL) enterotoxin complex and Bacillus cereus enterotoxin T (BceT) using polymerase chain reaction technique with specific primers. The results indicate that P. polymyxa PKPB1 does not carry any of hblA, hblD, hblC and bceT genes. The information generated through these studies addresses some of the regulatory requirements identified by the federal regulator, Health Canada's Pest Management Regulatory Agency (PMRA).

Commercialization efforts have resulted in the establishment of several contacts with U.S. companies who have expressed an interest in potential further development of PKPB1 with the Alberta Research Council.

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