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Abstract

Farmers have a serious economically harmful pest problem which urgently requires solving. Growers of winter oilseed rape (WOSR) have limited options available for controlling a major pest, the cabbage stem flea beetle, which has developed significant resistance to the only remaining authorized chemical insecticide (pyrethroid). Both larvae and adults also cause significant problems for other brassica crop growers (broccoli, cabbage, cauliflower, kale). This collaboration between RNA AgriBio Ltd, University of Plymouth and ÎåÒ»³Ô¹Ï×îйÙÍø will develop sequence specific RNA molecules encapsulated in a protective peptide wrapper to control cabbage stem flea beetle in a species-specific manner. This new RNA insecticide technology when sprayed onto crops will only harm the target pest, leaving beneficial insects and the environment unharmed. Our innovation and new approach to pest control is specifically focused on the use of peptides to deliver double stranded RNA (dsRNA) into cells of adult and larva Cabbage Stem Flea Beetle (CSFB: Psylliodes chrysocephala). A suitable target gene of the CSFB pest will be selected for gene knockdown/suppression. Sprayed onto oilseed rape cotyledons our protectively encapsulated dsRNA sequences is ingested by the pest and absorbed through the gut tissue. There, within the cells the degradation of the targeted gene transcript will occur by a process known as the RNA interference (RNAi) enzymatic pathway which is ubiquitous throughout nature. The RNAi pathway has evolved within cells over billions of years as protection against invasion of harmful RNA viruses. Almost all organisms have the RNAi pathway within their cells and beetles are particularly efficient at RNAi. To date there has been minimal research of this delivery method applied to pesticide research. However, similar approaches have already been tested and have proven to be possible in controlled laboratory/greenhouse conditions. For example, a Spray Induced Gene Silencing (SIGS) RNAi method which targeted aphids achieved 80% mortality by suppression of an aphid gene associated with feeding behaviour. A similar proof of concept method recently done at Plymouth University achieved partial mortality in CSFB when we targeted its specific actin gene, important for cellular integrity. This project will help develop this encouraging progress further. This will be off immense benefit to the UK oilseed rape sector and world agriculture.

Description

This project seeks to investigate a new solution for overcoming Cabbage Stem Flea Beetle, the most serious insect pest problem faced by winter oilseed rape farmers. If successful it will benefit:

Productivity. More yield will be obtained as crop losses from pest damage will be reduced. Our innovative approach increases efficiency for end users by using potentially more effective and safer control methods than currently available pesticides.

Sustainability and environmental impact. RNA interference (RNAi) based pest control can make a major contribution to sustainable agriculture because RNA spray applications can be designed with highly specific targeting to the pest species, leaving non-target species unharmed. Furthermore, the current chemical methods of controlling CSFB principally with pyrethroid sprays is highly toxic to adjacent habitats such as water bodies. A major disadvantage of the status quo of chemical insecticides is that they kill non-target species, reducing biodiversity in agricultural ecosystems. This has been of particular importance with regards to natural crop pollinators such as bumblebees, whose populations have been significantly affected by widespread pesticide use resulting in the need for assisted pollination.

Progression towards net zero emissions. The UK's ambition of net zero greenhouse gas emissions by 2050 will require reduction of emissions and improvements in carbon capture. Existing WOSR production efficiency can be improved by reduction of crop losses due to CSFB damage thereby requiring less planted area and fossil fuel burnt for crop tillage and replanting. Reduction of oilseed imports and the involved transport will reduce carbon dioxide emissions. Within soils more carbon capture can occur when the diversity and populations of soil living organisms are not harmed by current methods of chemical insecticide control. Carbon capture by soils should be enhanced by using environmentally benign RNA pesticide formulations. .

Resilience. Improved resilience to fight climate change can occur with improved soil biodiversity and soil carbon sequestration. Protection of soil health is an urgently required goal and a key aspiration of combatting climate change in agriculture. Soil security is linked to food production security and both are global existential challenges. A recent meta-analysis of 400 previous studies (Gunstone, 2021, Front. Environ. Sci.), found that chemical pesticides significantly harm soil invertebrates. If agroecosystems are to be resilient against climate change, a radical change of approach is required to protect soil biodiversity, and engineer in carbon sequestration. RNA pesticides offer a way forward as a saviour strategy to protect the soil invertebrate ecosystem.