Novel delivery of phytochemicals for sustainable crop protection

Abstract

New solutions for managing insect pests are urgently needed due to evolution of resistance to current insecticides. Insect pests cause annual losses of US$17.7 billion to the Brazilian economy. Our project focuses on development and bioactivity testing of nanotech and metallic coordination complexes as novel delivery mechanisms for bioactive phytochemicals, to provide new options for crop protection. By using defensive non-host phytochemicals, outside the metabolome of inbred crops, we can deliver phytochemicals that crop pests have not evolved with. UK-Brazil collaboration provides an ideal opportunity to share expertise and strengthen this new and promising area of research. The Stage 1 (pump-priming) project has successfully shown that nanoformulation and complexing of phytochemicals can solve low solubility issues, improve longevity of release and alleviate phytotoxicity; three major issues that have impeded the development of botanical insecticides to date. Furthermore, our early (proof of concept) phytochemical treatments have good efficacy, causing > 80% mortality of four major insecticide resistant pest species that are plaguing Brazilian agriculture (whitefly, Bemisia tabaci; fall armyworm, Spodoptera frugiperda; Western flower thrips, Frankliniella occidentalis, and peach-potato aphid, Myzus persicae). Treatments were also shown to strongly and significantly inhibit aphid reproduction (near complete shutdown) and had highly significant repellent activity. Stage 1 established a new collaboration between Biologists at Keele University (UK) and Chemists at the Federal University of São Carlos (UFSCar, Brazil), which was further strengthened by inclusion of crop protection expertise at São Paulo State University (UNESP, Brazil). The project has benefited from Keele Nanoceutics expertise, allowing low cost nanotech technologies from medical research to be translated into the agricultural field. Investment in Stage 1 has thus provided a solid foundation for future research. The Stage 2 project will use the collaboration established in Stage 1 to move towards generating new commercially viable phytochemical treatments. Workshops and exchange visits will be held to allow research groups to share expertise and work together. We have three workshops planned: UNESP (June 2019), Keele (Jan 2020) and UFSCar (Jan 2021). Experimental work will focus on three main areas: 1) Development and optimisation of phytochemical delivery using nanoformulation and complexing techniques. Treatments will be scaled up from leaf discs to whole plants with detailed investigation of two promising routes for application: sprayable formulations and systemic uptake via root drench treatments. 2) Testing bioactivity of formulations against economically important Brazilian crop pest targets. Antibiotic, antifeedant and repellent activity will be tested for using established methods we have developed for the four species. 3) Environmental and target specificity assessment. Most of the phytochemicals and formulations we are testing are already widely used as food ingredients, in medicine or in aromatherapy. However, we will obtain evidence in order to make the case for subsequent commercialisation of treatments. Breakdown of new biodegradable formulations will be measured. Non-target effects will be assessed with mammalian cell lines, an egg parasitoid wasp Trichogramma pretiosum, a beneficial natural enemy, and the honeybee, Apis mellifera. We have shown cross-fertilisation between the disciplines involved in the project, allowing Agriculture to advance by using approaches already developed in Chemistry and Medicine. Our hypothesis is that herbivore insects are susceptible to defensive phytochemicals produced by non-host plants on which they have not evolved and that they can be applied to crops using new formulation technologies. The Stage 2 project has considerable potential to generate much needed new tools for managing crop pests. (AU)