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Plant-Virus Interactions Group

Funded PhD projects for 2020 entry:

  • A major virus threat to UK crops
  • Understanding and engineering virus resistance in plants

Deadline for application: 7 June 2020

Group Leader: Dr John A Walsh

Summary of group’s activities:

Viruses transmitted by aphids. Much of our research is focussed on plant–virus interactions, particularly Turnip mosaic virus–Brassica and Arabidopsis interactions. We are identifying, characterising and mapping natural plant resistance genes to Turnip mosaic virus (TuMV) and looking at how they recognise TuMV and how TuMV can overcome resistance.

We are also looking at virus–virus interactions and how these are mediated through the plant. One aspect relates to the use of mild isolates of viruses to protect plants against severe isolates (cross-protection). Another investigates the co-evolution of TuMV and wild brassica plant communities.

Viruses transmitted by fungi and similar organisms (protists). We have identified the virus Watercress yellow spot virus transmitted by Spongospora subterranea f.sp. nasturtii and have been working on those transmitted by Olpidium brassicae that cause lettuce big-vein disease. Control strategies for the vectors (by biological and chemical control and by using disinfectants) and natural plant resistance to the viruses (WYSV and big-vein) have been developed.

Current Projects:

  • Understanding the mechanisms of Brassica resistance genes to Turnip mosaic virus (BBSRC funded)
  • Molecular characterisation of virulence determinants to Turnip mosaic virus for the Brassica resistance gene TuRB01 (MSc studentship)
  • Identifying, characterising and mapping resistance genes to Turnip mosaic virus in different Brassica species (Defra funded)
  • Understanding the molecular mechanisms underlying cross-protection using TuMV and Cucumber mosaic virus (CMV) (Defra funded)
  • The genomics of plant-virus co-evolution in wild Brassica species (NERC funded)
Our aim is to:
  • Reduce pesticide inputs to crops by developing non-chemical means of controlling plant viruses
We can achieve this by:
  • Understanding how natural plant resistance to viruses works in order to try to deploy plant resistance genes in a durable manner, thereby reducing the pesticide inputs (that growers have to use in order to stop insect vectors spreading plant viruses) in food plants.
  • Determining how different virus isolates interact within plants and how virus isolates inducing mild symptoms can be used to protect plants against severe isolates.
We also work on natural virus infections of wild plants in order to:
  • Understand the natural ecology of plant viruses in wild plants communities
  • Study the co-evolution of viruses and plants in natural communities
  • Other aspects of our research programme have been funded by Defra, BBSRC, HDC, NERC, EC, the Environment Agency, DFID, The Royal Society and Horticulture Link.

Contact details:

For further information/enquiries contact John Walsh:


We currently have a diverse range of collaborators in the UK and overseas including: Dr Fernando Ponz’s group, INIA, Madrid; Dr Isobel Parkin’s and Prof Derek Lydiate’s groups, Agriculture Canada, Saskatoon; Dr Xiaowu Wang and Dr Rifei Sun’s groups, CAAS, Beijing; Syngenta Seeds.


Resting spores of Olpidium brassicae as seen in the light microscope
A cabbage head that has been cut open to reveal  internal necrosis caused by Turnip mosaic virus
Rod-shaped particles of Turnip mosaic virus as seen in the transmission electron microscope
Brassica plants challenged with Turnip mosaic virus showing susceptible plants (left) and resistant plants (right) possessing the resistance gene TuRB01
An aphid (Myzus persicae) vector of brassica viruses as seen in the scanning electron microscope
A section of a plant cell showing the cytoplasmic inclusion bodies of Turnip mosaic virus as seen in the transmission electron microscope
A lettuce plant in the field showing symptoms of lettuce big-vein disease
Brassica leaves, on the right infected by Turnip mosaic virus expressing the green fluorescent protein (GFP) and a healthy leaf on the left, as seen in ultraviolet light