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Professor John Carr


Brief Summary

The student will explore the hypothesis that bees not only benefit plants through pollination but may also carry viruses that are harmful to pest insects and may provide an adjunct to plant innate defence mechanisms  
Importance of Research
Aphids are sap-sucking insects that damage plants and transmit most plant viruses. However, plant phloem sap can harbour aphid-infecting viruses that do not infect or damage plants but can be lethal to any aphids that feed on the phloem. We think that these viruses may provide a natural biocontrol for plants. We want to know how these viruses survive and spread in the plant, and how they affect the behaviour (sensing of visual and olfactory cues) and performance (mortality, reproduction, growth) of aphids to better understand them as natural biocontrol agents and if they can safety be exploited. This could provide an avenue for decreased use of pesticides and greater sustainability in agriculture.


Project Summary

Aphids are plant pests that cause direct damage to plants and carry plant-pathogenic viruses and bacteria. Aphids are currently controlled using insecticides that harm beneficial insects and pollute the environment. The use of insecticides is being restricted, and aphids are evolving resistance. Using biological agents that already occur in many wild and cultivated plants to control aphid populations would benefit non-pest insect populations including beneficial insects such as pollinators. Our previous work suggests that certain insect viruses (dicistroviruses) circulate between plants (in which these viruses cannot replicate or cause damage) and insects (including aphids and whiteflies) and might be carried by bees. Our hypothesis is that this is a natural form of biological control that supplements plants’ innate defences against insect herbivory. 


What will the successful applicant do?

Year 1 Use metagenomics to discover the range of insect hosts (predominantly aphid, whiteflies, bees) and wild and crop plant ‘infection reservoirs’ for aphid-pathogenic viruses present in our collection of insect and plant samples gathered from the UK and east and west Africa to further explore our hypothesis that dicistroviruses are involved in cross-species/cross-Kingdom circulation. 

Years 2-3 Establish dicistrovirus-carrying aphid and plant populations from material surveyed in year 1. Fallback use our characterised isolate of aphid lethal paralysis virus to explore if viruses can be transferred via the plant between aphids and possibly other insects under controlled conditions.


Training Provided 

Training will be provided in sequencing,  bioinformatics, entomological, virology and molecular ecological methods, plant techniques, and in-field insect capture and identification. 



Murphy, A.M., Jiang, S., Elderfield, J.A.D., Pate, A.E., Halliwell, C., Glover, B.J., Cunniffe, N.J., and Carr, J.P. (2023). Biased pollen transfer between virus-infected and non-infected plants by bumblebees favors the paternity of infected plants in cross-pollination. iScience 26(3): 106116.

Wamonje, F.O., Michuki, G.N., Braidwood, L.A., Njuguna, J., Mutuku, J.M., Djikeng, A., Harvey, J.J.W. and Carr, J.P. (2017). Viral metagenomics of aphids present in bean and maize plots on mixed-use farms in Kenya reveals the presence of three dicistroviruses including a novel Big Sioux River virus-like dicistrovirus. Virology Journal 14:188.

Groen, S.C., Jiang S., Murphy, A.M., Cunniffe N.J., Westwood, J.H., Davey, M.P., Bruce, T.J.A., Caulfield, J.C., Furzer, O.J., Reed, A., Robinson, S.I., Miller, E., Davis C.N., Pickett, J.A., Whitney, H.M., Glover, B.J. and Carr, J.P. (2016). Virus infection of plants alters pollinator preference: A payback for susceptible hosts? PLoS Pathogens 12(8): e1005790.


NERC C-Clear DTP / University Trust Funds (UF) / OTHER