June 8, 2005
Source: British Society for Plant Pathology, New Disease Reports, Vol. 11 [edited]
<http://www.bspp.org.uk/ndr/july2005/2005-46.asp>

A novel begomovirus with distinct genomic and phenotypic features infects tomato in Bangladesh
M. N. Maruthi, Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK; A. R. Rekha (as for Maruthi);S. N. Alam, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh; K. A. Kader (as Alam); A. Cork (as for Maruthi); and J.Colvin (as for Maruthi) Accepted for publication 10 May 2005.

In Bangladesh tomato is cultivated over ca. 40 000 acres annually. Tomato leaf curl virus disease (ToLCVD) normally reduces tomato production significantly, often causing up to 100 percent yield loss. Diseased tomato plants were collected from Joydebpur, Bangladesh, in September 2003, because they exhibited unusually mild ToLCVD symptoms of yellowing and leaf curling. In addition, "mosaic-like" symptoms developed on the older leaves of the susceptible tomato variety "Moneymaker", which is atypical for leaf curl- inducing viruses.

Total DNA was extracted from leaves with symptoms and putative viral genomes were amplified by PCR using degenerate primers specific to DNA-A and -B and DNA-beta molecules. Sequences generated from the amplicons were either used to design virus-specific primers or to obtain directly complete viral sequences. A previously undescribed monopartite begomovirus, designated Tomato leaf curl Joydebpur virus-Mild (ToLCJV-Mld), was found associated with these mild symptoms. Based on DNA-A sequences (2761 nucleotides, EMBL Accession No.
AJ875159), ToLCJV-Mld was most similar to Pepper leaf curl Bangladesh virus (AF314531) at 87.1 percent nt [nucleotide] identity. ToLCJV-Mld satellite DNA- molecule (1366 nt, AJ966244) shared highest (59.0 percent) nt identity with a molecule isolated from ToLCVD in India (AY438558). No DNA-B component was detected.

The number and arrangement of ToLCJV-Mld DNA-A open reading frames (ORFs) was identical to monopartite begomoviruses, except that an additional ORF of 849 nt (282 amino acids) was predicted to occur on the complementary strand between nt positions 1139 and 291 encompassing the entire length of the coat protein gene. The association of a DNA-beta molecule with begomoviruses is known to cause severe symptoms, but to our knowledge this is the 1st report where it was associated with mild symptoms. ToLCJV-Mld DNA-A shared 86.0
percent and 74.4 percent nt identities with the previously reported Tomato leaf curl Bangladesh virus (AF188481) and Tomato leaf curl New Delhi virus- Severe [Jessore] (AJ875157), respectively.

These results confirm the occurrence of at least 3 begomovirus species in tomato in Bangladesh.

References
----------
Briddon RW, Bull SE, Mansoor S, Amin I, Markham PG, 2002. Universal primers for the PCR-mediated amplification of DNA: A molecule associated with monopartite begomoviruses. Molecular Biotechnology 20, 315-318.

Green SK, Tsai WS, Shih SL, Black LL, Rezajan A, Rashid MH, Roff MMN, Myint YY, Hong LTA, 2001. Molecular characterisation of begomoviruses associated with leafcurl diseases of tomato in Bangladesh, Laos, Malaysia, Myanmar and Vietnam. Plant Disease 85, 1286.

Maruthi MN, Rekha AR, Cork A, Colvin J, Alam SN, Kader KA, (submitted). First report of Tomato leaf curl New Delhi virus infecting tomato in Bangladesh. Plant Disease

Muniyappa V, Maruthi MN, Babitha CR, Colvin J, Briddon RW, Rangaswamy KT, 2003. Characterisation of pumpkin yellow vein mosaic virus from India. Annals of Applied Biology 142, 323-331.

--
ProMED-mail
<promed@promedmail.org>

[Plant virologists continue to report new begomoviruses, and new ones will undoubtedly emerge. The combination of high temperatures, presence of high populations of whiteflies, and suitable natural host plants apparently results in a mix that is conducive to generating new begomovirus strains in the region. The most significant aspect of this piece is the interaction between Mungbean yellow mosaic India virus (MYMIV-[cowpea strain]) and its DNA satellite (beta). Plants infected by MYMIV satellite DNA-beta express more severe symptoms compared to those inoculated with MYMIV alone. Similar results have been reported for other DNA-beta molecules and viruses. The begomovirus-satellite disease complexes are associated with economically important diseases and have been isolated from vegetable and fiber crops, ornamental plants, and weeds throughout Africa and Asia. Their widespread distribution and diversity, coupled to the global movement of plant material and the dissemination of the whitefly vector, suggests that these disease complexes pose a serious threat to tropical and sub-tropical agro-ecosystems worldwide.

Disease management of ToLCV and other begomoviruses depends on preventing movement of _Bemisia tabaci_ [Bt] -infected plants (e.g. tomato transplants) to virus-free areas, where the virus can become established. Various control options include removal of infected plants (roguing, removal, or burial of infected crop residues) and intercropping in combination with chemical insecticides and use of available resistant cultivars. Use of plastic UV- absorbing screening material to exclude Bt is another method. Genetic resistance to begomoviruses has been reported in some wild _Lycopersicon_ species such as _L. hirsutum_ and _L. peruvianum_ which might be transferred to tomato. In Pakistan, resistance to leaf curl virus has been incorporated into tomato and chili cultivars. - Mod.DH

Links:
<http://gemini.biosci.arizona.edu/viruses/peplcbv/index.html>
<http://gemini.biosci.arizona.edu/viruses/tolcndv/index.htm>
<http://www.seedquest.com/News/releases/2004/november/10534.htm>]