New Disease Reports
New Disease Reports (2012) 25, 1. [http://dx.doi.org/10.5197/j.2044-0588.2012.025.001]
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New virus detected on Nasturtium officinale (watercress)

V. Harju 1*, A. Skelton 1, S. Forde 1, S. Bennett 1, R. Glover 1, W. Monger 1,2, I. Adams 1, N. Boonham 1 and A. Fox 1

*val.harju@fera.gsi.gov.uk

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Received: 07 Oct 2011; Published: 27 Jan 2012

Keywords: next generation sequencing, tymovirus

Nasturtium officinale (watercress) is a semi-aquatic, high value, leaf and stem crop. As a member of the family Brassicaceae (Cruciferae), it has a variety of culinary, medicinal and cosmetic uses. In 2009 watercress samples from Spain were received for virus testing. The leaves had symptoms of vein clearing with the veins appearing white, with chlorotic spotting and distortion (Fig. 1). The prominent, raised leaf veins had led to a number of customer rejections due to undesirable appearance. In severe cases breakdown of the raised vascular system was causing the ingress of opportunistic plant pathogens such as a Pseudomonas sp. having a direct effect on the crop shelf life. Overall, the crop was unmarketable.

The sample tested negative by ELISA for known watercress viruses such as Turnip mosaic virus, Tomato aspermy virus, Broad bean wilt viruses 1 and 2, Cucumber mosaic virus and Watercress yellow spot virus (WYSV). Further testing by sap inoculation followed. Six days after inoculation, local chlorotic spots were noted on Nicotiana occidentalis P1 and similarly on N. benthamiana after 13 days. No virus reaction was seen on Chenopodium quinoa, C. amaranticolor, . hesperis, N. clevlandii, N. glutinosa, or Petunia sp. This further differentiates the new virus from WYSV which is reported to induce symptoms on C. quinoa and N. clevlandii (Walsh & Phelps, 1991; Walsh et al., 1989) or Watercress chlorotic leaf spot virus which is reported to induce symptoms on C. quinoa and C. amaranticolor (Tomlinson & Hunt, 1987). A sample of plant material infected with the new virus was then sequenced with a Roche 454 FLX system using the methods described in Adams et al., (2009). Out of 55140 readings obtained, 13122 contained tymovirus-related sequences. From these readings a coat protein sequence was assembled (GenBank Accession No. JN808774) and compared to that of existing viruses. The new virus is a tymovirus related to Turnip yellow mosaic virus (TYMV). Fig. 2 shows a neighbour-joining tree of related coat protein sequences constructed using MEGA (Kumar et al., 2008). The coat protein sequence of the new virus is only 82% similar to its closest neighbour, TYMV, and thus constitutes a new viral species according to ICTV guidelines (Fauquet et al., 2005). We propose the tentative name of Watercress white vein virus(WWVV) for this new virus.

Figure1+
Figure 1: Watercress leaf showing the prominent white veins and chlorotic leaf margin (left); uninfected watercress leaf (right).
Figure 1: Watercress leaf showing the prominent white veins and chlorotic leaf margin (left); uninfected watercress leaf (right).
Figure2+
Figure 2: Phylogenetic tree of the coat protein sequences of related viruses in Tymovirales.
Figure 2: Phylogenetic tree of the coat protein sequences of related viruses in Tymovirales.

Acknowledgements

We would like to thank JamesHarper, Product Manager, The Watercress Company, Waddock Cross, DT2 8QY, UK for sending these samples to us from his growers. This work was funded by the EU-Qbol project. Antisera of WYSV was a gift from John Walsh, University of Warwick, UK.

References

  1. Adams IP, Glover RH, Monger WA, Mumford R, Jackeviciene E, Navalinskiene M, Samuitiene M, Boonham N, 2009. Next-generation sequencing and metagenomic analysis: a universal diagnostic tool in plant virology. Molecular Plant Pathology, 537-45 [http://dx.doi.org/10.1111/j.1364-3703.2009.00545.x]
  2. Fauquet CM, Mayo MA, Maniloff J, Desselberger U, Ball LA, eds, 2005. Virus Taxonomy. Eighth Report of the International Committee on Taxonomy of Viruses. San Diego, CA, USA: Academic Press.
  3. Kumar S, Nei M, Dudley J, Tamura K, 2008. MEGA: A biologist-centric software for evolutionary analysis of DNA and protein sequences. Brief Bioinformatics 9, 299-306. [http://dx.doi.org/dx.doi.org/10.1093/bib/bbn017]
  4. Tomlinson JA, Hunt J, 1987. Studies on watercress chlorotic leaf spot virus and on the control of the fungus vector (Spongospora subterranea) with zinc. Annals of Applied Biology , 75-88. [http://dx.doi.org/10.1111/j.1744-7348.1987.tb03234.x]
  5. Walsh JA, Phelps K, 1991. Development and evaluation of a technique for screening watercress (Rorippa nasturtium-aquaticum) for resistance to watercress yellow spot virus and crook-root fungus (Spongospora subterranea f. sp. nasturtii). Plant Pathology 40, 212-20. [http://dx.doi.org/10.1111/j.1365-3059.1991.tb02369.x]
  6. Walsh JA, Clay CM, Miller A, 1989. A new virus disease of watercress in England. EPPO Bulletin 19, 463-70. [http://dx.doi.org/10.1111/j.1365-2338.1989.tb00420.x]
To cite this report: Harju V, Skelton A, Forde S, Bennett S, Glover R, Monger W, Adams I, Boonham N, Fox A, 2012. New virus detected on Nasturtium officinale (watercress). New Disease Reports 25, 1. [http://dx.doi.org/10.5197/j.2044-0588.2012.025.001]

©2012 The Authors