The need for new control agents for viruses, insect pests and diseases grows each year, driven by the need for greater production and climate driven pest and disease expansion. Viruses are one of the major plant diseases and responsible for about ~US$50b/annum production loss with few, if any, commercially available products available for their control. At the same time finding new modes of actions to combat pest resistance development is increasingly difficult, due in part to community and regulatory demands. The cost of developing a single new chemical crop protection agent is now commonly stated as being above US$250m.
In this context, the use of RNA silencing (RNAi) plant defence mechanisms offers a significant opportunity to address crop protection needs. Research has demonstrated that the application of double stranded RNA (dsRNA) onto plants will confer viral resistance. Naked dsRNA can transfect plant cells when topically applied to leaf material and can infer protection against viral disease for up to 7 days (Gan 2010). The single biggest inhibitor to realising the full potential of the RNAi technology is the ability to deliver the dsRNA constructs into the plant cell and maintain its activity over extended periods of time.
A Layered Double Hydroxide (LDH) nanoparticle has been developed at the University of Queensland that can load dsRNA (300-2000bp RNAi) to form a slow release capsule. This nanoparticle delivery mechanism gives a sustained, adjustable, slow-release of dsRNA to plants following topical application, giving viral protection. This technology opens the potential to combine a range of different, very selective RNAi control agents into one spray.