| Abstract |
Protecting crops against damping-off diseases is a global issue Multiple crops are killed after planting and during germination by damping-off diseases. Controlling these diseases is required for food security and is a global, billion dollar market. Chemical pesticides are used to kill the pathogenic oomycete and fungal microbes that cause damping-off, but due to environmental toxicity, market withdrawal, and pathogen resistance, alternative control measures are urgently needed. In Europe, two chemical pesticides, thiram and metalaxyl, were recently withdrawn leaving UK pea growers with no means of damping-off control. Microbial biopesticides offer a natural, affordable and sustainable solution for crop protection. However, one group of bacteria called Burkholderia have not been fully harnessed even though they make many protective natural bioactives. In the US, Burkholderia biopesticides were used commercially until 1999, but because they can cause human infections in vulnerable people, a moratorium on the registration of such “opportunistic” disease-causing bacteria was established. Safety – the barrier to overcome for a route to market From our BBSRC funding we have found ways to produce safer Burkholderia biopesticides. We were also able to move the genes that encode the Burkholderia anti-damping off activity into inherently safe Paraburkholderia bacteria. Our route to market will be to prove the safety of our prototype biopesticides, and with sufficient evidence of this in place, and seek investment for full field testing and registration of the inventive biopesticides. BBSRC funding was used to identify how the biopesticides work Via BBSRC-funding to identify antibiotic-making genes in Burkholderia bacteria, we found many strains produced multiple novel antibiotics. Using further BBSRC funding, we identified the Burkholderia genes that make antimicrobials called polyynes and proved these metabolites acted to the prevent damping-off disease. Bacterial polyynes kill multiple oomycete and fungal diseases pathogens. We have shown that polyynes are most effective when specifically delivered by Burkholderia bacteria coated onto a crop seed. During germination the polyynes are delivered directly to the roots by the bacteria, mediating a targeted and localised protection against damping-off disease. A biopesticide development plan based on expert consultation Two prototype biopesticides will be constructed in our development plan and tested for safety as follows. 1. Construct an inventive, gene-edited and re-purposed Burkholderia ambifaria biopesticide with enhanced safety To improve safety in Burkholderia biopesticides, we removed their third chromosome DNA by genetics. This deletes 1000s of pathogenic genes and resulted in strain which could not survive in a mouse lung infection model, but retained its biopesticidal ability. This engineering of Burkholderia was not considered inventive by a patent attorney because the chromosome deletion strategy was published by others. Having now shown excellent crop season protection with the chromosome deletion Burkholderia, our position to develop an inventive strain is strengthen. We will therefore make proprietary gene-edits to remove antimicrobial resistance and pathogenicity genes, producing a safer strain, repurposed from the historically effective and commercially successful Burkholderia biopesticide. 2. Optimise a plant-growth promoting and polyyne-producing Paraburkholderia biopesticide We have also moved the polyyne-making genes from Burkholderia into safe and plant-beneficial Paraburkholderia bacteria which cannot at 37oC. The engineered Paraburkholderia are were considered inventive and with the excellent damping-off protection they delivered, the strategy was patented. However, we need to optimise a Paraburkholderia prototype by selecting a strain that is optimal for protection and plant growth promotion, and also removing the extra genetic engineering DNA to leave just the polyyne pathway in the prototype biopesticide. 3. Testing the safety of the Burkholderia and Paraburkholderia biopesticide prototypes To establish the basis for a route to market, the safety of the Burkholderia and Paraburkholderia prototypes will be tested. This will primarily focus on establishing human safety, but also account for additional plants insect, and general ecotoxicity. Safety testing will be carried out using accredited commercial service providers that work to the regulatory standards. 4. Undertake expert consultation and commercial networking to seek investment for the route to market With safety established and IP secured for our prototype biopesticides, we will work with our project consultants and partners to seek investment for their full regulatory testing and registration. The US biopesticide market will be our primary target as it allowed historical commercial use of Burkholderia biopesticides and permits the registration of genetically modified field agents. |