In the UK, some 30 aphid species are pests of a wide range of arable and horticultural crops, causing potential economic losses in excess of £100 million per year as a result of direct feeding damage and the virus diseases which they spread.  Slightly more than half of all the known plant viruses are transmitted by aphids and more than 200 aphid species have been reported to transmit viruses. Our research aims to determine what makes one aphid a vector, when another species or even biotype is not, and to understand how these viruses spread in the environment. The biological processes involved in transmission differ between viruses.  This has important consequences for the epidemiology of the diseases they cause, and the methods devised for their control.

Potato leafroll virus (PLRV) and Potato virus Y (PVY) cause the most important aphid-borne virus diseases in potato crops, decreasing yields by 50-80% in crops grown from infected seed.

Over-use of insecticides has undesirable effects on the environment and promotes the selection of insecticide-resistant aphids. Our work focuses on the identification of other epidemiological components of potato virus pathosystems, in particular:

• the effects on PLRV acquisition and transmission from infected potato genotypes in which virus accumulation is restricted
• variations in virus structure and aphid biotype that result in poor transmission of PLRV
• molecular identification of genotypes of Myzus persicae, linked to biological traits and geographical origins
• identification of PVY vectors and virus sources.

Virus transmission during climate change

Interest in climate change has dramatically increased as the impact on our environment has become more obvious. It has become clear that plants and animals in general are becoming active earlier each year. This does not necessarily mean that there are going to be more pests, as natural control mechanisms can also shift. The effect this will have on the prevalence of virus in the Scottish seed potato crop is being studied at SCRI. In the laboratory it is only possible to measure components of the bigger problem and our research is currently examining the effects of climate change on the transmission of potato viruses. The research will take into account new information about the variation found within Scottish populations of virus vector aphids, including information on insecticide resistance and ecology. Studies will make use of the most effective means of measuring virus transmission at both a biological and molecular level, which we have developed. The project outputs will in turn contribute information to the multi-institute cross-cutting theme on climate change and be passed on to the industry via agronomists.

Selected publications

Kasprowicz, L., Malloch, G., Foster, S., Pickup, J., Zhan, J. and Fenton, B. 2007. Clonal turnover of MACE-carrying peach-potato aphids (Myzus persicae (Sulzer), Homoptera: Aphididae) colonizing Scotland. Bulletin of Entomological Research (in press).

Malloch, G., Borthwick, F., Kasprowicz, L., Pickup, J., Neilson, R. and Fenton, B. 2006. Analysis of peach-potato aphids (Myzus persicae (Sulzer), Homoptera: Aphididae) caught in Scottish suction traps using microsatellite markers. Bulletin of Entomological Research 96, 563- 582.

Fenton, B., Malloch, G., Woodford, JAT. Foster, S.P., Anstead, J., Denholm, I., King L. and Pickup J. 2005. The Attack of the Clones: Tracking the Movement of Insecticide Resistant Peach Potato Aphids (Myzus persicae). Bulletin of Entomological Research 95, 483-494.

Gildow, F.E., Reavy, B., Mayo, M.A., Duncan, G.H., Woodford, J.A.T., Lamb, J.W. and Hay R.T. 2000.  Aphid acquisition and cellular transport of Potato leafroll virus-like particles lacking P5 readthrough protein. Phytopathology 90, 1153-1161.

Fenton, B., Woodford, J.A.T. and Malloch, G. 1998. Analysis of clonal diversity of the peach-potato aphid, Myzus persicae (Sulzer), in Scotland, UK and evidence for the existence of a predominant clone. Molecular Ecology 7, 1475-1487.

Jones, D.A.C., Woodford, J.A.T., Main, S.C., Pallet, D. and Barker, H. 1996. The role of volunteer potatoes in the spread of potato virus YN in ware crops of cv. Record. Annals of Applied Biology 129, 461-478.

Robert, Y., Woodford, J.A.T. and Ducray-Bourdin, D.G. 2000. Some epidemiological approaches to the control of aphid-borne virus diseases in seed potato crops in northern Europe. Virus Research 71, 33-47.

Woodford, J.A.T. 1999. Comparison of sticky thread traps and yellow water traps for monitoring PVY vector aphids in potato fields. Proceedings Crop Protection in Northern Britain 1999, 267-272.

Woodford, J.A.T., Jolly, C.A. and Aveyard, C.S. 1995. Biological factors influencing the transmission of potato leafroll virus by different aphid species. Potato Research 38, 133-141.

Barker, H. and Woodford, J.A.T. 1992. Spread of potato leafroll virus is decreased from plants of potato clones in which virus accumulation is restricted. Annals of Applied Biology 121, 345-354.

Woodford, J.A.T. 1992. Virus transmission by aphids in potato crops. Netherlands Journal of Plant Pathology 98, Supplement 2, 47-54.