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Carrot Viruses

The interaction between populations of pathogens in wild hosts and in cultivated ones can be crucial to understanding and controlling some diseases. No where is this more clearly true than in the case of parsnip yellow fleck virus (PYFV). This virus requires a helper virus for transmission (anthriscus yellows – AYV) but AYV cannot infect carrots; this means all infection of carrots is derived directly from infection of wild hosts.

We are undertaking a Defra-funded project to look at two virus complexes in members of the Apiaceae (carrots and their relations):

  • PYFV/AYV
  • carrot motley dwarf (CMD) complex of three viruses

The first of these causes damaging outbreaks every few years and the challenge is understand what triggers these sporadic occurrences. The second (CMD) occurs regularly but generally at only low levels due to the regular applications of insecticides. If, as thought possible, the use of insecticides is greatly reduced due to new regulations, CMD may well become much more frequent and important growers.

This project on pathogens in wild hosts also includes work on Sclerotinia lead by Dr John Clarkson.

Within the project we are comparing virus populations in a range of possible wild hosts with isolates found in carrots. We are also doing a little work on the aphid vector (primarily the carrot willow aphid, Cavariella aegepodii).

Once we understand the sources of infection in carrot we will be looking at new approaches to managing the interaction to minimise infection.

aphids on cow parsley
Aphids on cow parsley
 
symptoms of carrot motley dwarf
Symptoms of carrot motley dwarf