New Disease Reports
New Disease Reports (2003) 7, 17.
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Carrot Red Leaf Associated RNA in Carrots in the United Kingdom

A. Morton, N.J. Spence, N. Boonham and D.J. Barbara*

*dez.barbara@hri.ac.uk

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Accepted: 07 Apr 2003

Carrot red leaf associated RNA (CtRLVaRNA) was originally described in Californian carrots (Daucus carota L.) (Watson et al., 1998). It has also been reported from parsley (Petroselenium crispum) in Belgium (Vercruysse et al., 2000). CtRLVaRNA is thought to be replication independent but is dependent on carrot red leaf virus (CtRLV) for cell-to-cell movement and aphid transmission (Falk et al., 1999). In California CtRLVaRNA was found in conjunction with the two previously identified components of carrot motley dwarf complex (CMD), viz. CtRLV and carrot mottle (CMoV) virus.

During July 2002, six samples of carrot leaves, selected for CMD-like symptoms, were collected from four fields in Lancashire, U.K. An additional 40 samples from symptomless plants (each sample comprised leaves from five plants) were taken from 20 fields in Lancashire, Yorkshire, Nottinghamshire and East Anglia. Primer CtRLVaRNA-2 (5'-ACCCTCCCCTGTAGTTC-3') was used for reverse transcription, and this primer plus CtRLVaRNA-1 (5'-TCTAGTTTCTCTCAAGTTCCA-3') (Vercruysse et al., 2000) for standard PCR reactions (annealing temperature 52°C) on total RNA extracts of carrot leaves. Samples were also tested for CtRLV and CMoV by RT-PCR.

All six plants showing symptoms were positive for CtRLVaRNA. CtRLV and CMoV were also present in these samples. CtRLVaRNA was found in five of the 40 bulk samples; four had all three viruses while one had CtRLV but not CMoV. The CtRLVaRNA infected bulk samples represented three fields in East Anglia and one in Yorkshire.

Identification of the virus as CtRLVaRNA was confirmed by sequencing six amplicons representing isolates from all three UK regions where infection had been detected. All the UK sequences were similar to those of two Californian isolates, a8 and a25 (Accession numbers AF020616, AF020617). The UK isolates were all distinct, differing from each other by between 0.6% and 13.3% (with aligned sequence lengths of 324 nts); the two Californian isolates differed from each other by 13.9%.

This is the first report of CtRLVaRNA in carrots in the UK or, indeed, anywhere outside California.

Figure1+
Figure 1: Figure: 1 Cladogram showing nucleotide divergence between six UK and two Californian isolates of CtRLVaRNA
Figure 1: Figure: 1 Cladogram showing nucleotide divergence between six UK and two Californian isolates of CtRLVaRNA

Acknowledgements

This work was funded by DEFRA, HDC, ACRS, Huntapac and PlantSystems through HortLINK project 248.

References

  1. Falk BW, Tian T, Yeh H-H, 1999. Luteovirus-associated viruses and subviral RNAs. Current Topics in Microbiology and Immunology 239, 159-75.
  2. Vercruysse P, Gibbs M, Tirry L, Höfte M, 2000. RT-PCR using redundant primers to detect the three viruses associated with carrot motley dwarf disease. Journal of Virological Methods 88, 153-61.
  3. Watson MT, Tian T, Estabrook E, Falk BW, 1998. A small RNA resembling the beet western yellows luteovirus ST9-associated RNA is a component of the Californian motley dwarf complex. Phytopathology 88, 164-70.
This report was formally published in Plant Pathology

©2003 The Authors