June 2, 2005
Source: British Society for Plant Pathology, New Disease Reports, Vol. 11 [edited]
<http://www.bspp.org.uk/ndr/july2005/2005-51.asp>

Occurrence of Tomato chlorosis virus on tomato in Reunion Island
H. Delatte, CIRAD, UMR PVBMT C53 CIRAD-Universite de La Reunion, Pole de Protection des Plantes, Ligne Paradis, 97410 Saint-Pierre, La Reunion, France; F. Naze (as for Delatte); J.S. Cottineau, SCA VIVEA, 8 bis route de la ZI2, 97410 Saint Pierre, La Reunion, France; P. Lefeuvre (as for Delatte); B. Hostachy, Service de la Protection des Vegetaux, Pole de Protection des Plantes, Ligne Paradis, 97410 Saint-Pierre, La Reunion, France; B. Reynaud (as for Delatte); and J.M. Lett (as for Delatte) Accepted for publication 19 May 2005.

Pronounced yellowing symptoms on the lower and middle leaves of tomato plants, similar to those caused by magnesium deficiencies, were observed in 2004 and 2005 in farmers' greenhouses in Reunion Island. Fruits on such plants were smaller, and yields were indirectly affected. The flame-like pattern of the discolored leaves and the abundance of whiteflies on these plants suggested the possible involvement of Tomato chlorosis virus (ToCV)
or Tomato infectious chlorosis virus (TICV) (_Closteroviridae_, _Crinivirus_) (Wisler et al., 1998).

20 symptomatic leaf samples were collected from tomato plants in March 2005, and total RNA was extracted from these samples using the Qiagen RNeasy Plant Mini kit. For detection of a potential crinivirus, a nested PCR was performed (Dovas et al., 2002). The method consists of a 1-step RT-PCR using primers HS-11 and HS-12, followed by nested PCR with primers TIC-3/TIC-4 and ToC-5/ToC-6, for detecting TICV or ToCV respectively. These primers were designed to amplify the highly conserved region of the heat shock protein 70 gene. A PCR product at the expected size was observed with ToCV primers for 14 of the symptomatic leaf samples. No PCR product was observed for the PCR performed with TICV primers.

3 PCR products were cloned using pGEM-T easy vector system II (Promega, France) and sequenced (Genome Express, France) (Accession Nos AJ968394, AJ968395 and AJ968396). Sequences obtained from the 3 samples had 99.5 percent nucleotide identity when aligned (DNAMAN, Lynnon BioSoft, Quebec). The most significant sequence alignments (NCBI, BLASTn) were 98 percent with ToCV isolates from the USA (Accession No AF024630), Spain (Accession Nos AF233435, AF215818 and AF215817) and from Italy (Accession Nos AF234029 and AY048854).

To our knowledge, this is the 1st report of ToCV in Reunion Island.

References

Dovas CI, Katis NI, Avgelis AD, 2002. Multiplex detection of criniviruses associated with epidemics of a yellowing disease of tomato in Greece. Plant Disease 86, 1345-1349.

Wisler GC, Li HY, Lowry DS, Duffus JE, 1998. Tomato chlorosis virus: a new whitefly-transmitted, phloem-limited, bipartite closterovirus of tomato. Phytopathology 88, 402-409.

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[Criniviruses are filamentous viruses containing 2 separate genomic segments (650-850 and 700-900 nm), both of which are required for infectivity. Field and glasshouse tomato crops are the main host, but other crops such as potato (_Solanum tuberosum_) and lettuce (_Lactuca sativa_) are susceptible. 2 weed species (Jimson weed, _Datura stramonium_ and Black nightshade, _Solanum nigrum_) are also hosts that may contribute to
maintaining these viruses in the wild. TICV is transmitted only by _T. vaporariorum_, but ToCV is transmitted by the greenhouse whitefly (_Trialeurodes vaporariorum_), the banded-wing whitefly (_T. abutilonea_), and by _Bemisia tabaci_ (biotype A) and _B. argentifolii_ (biotype B). Once either virus is established in an agricultural environment containing susceptible hosts, it is very difficult to prevent infection. Disease management requires use of virus-free transplants, avoidance of susceptible hosts (especially weeds), roguing (physical removal) of infected plants, and control of insect vectors by chemical insecticides. - Mod.DH]