January 26, 2005
Source: British Soc. Plant Pathol., New Disease Reports, Vol. 10 [edited]

A new begomovirus isolated from Gossypium barbadense in Southern India
R.V. Chowda Reddy, Plant, Animal and Human Health Group, Natural Resources Institute, University of Greenwich at Medway, Kent, ME4 4TB, UK; V. Muniyappa, Department of Plant Pathology, University of Agricultural Sciences, GKVK, Bangalore-560065, India; J. Colvin (as for Chowda Reddy); and S. Seal (as for Chowda Reddy). Accepted for publication 20 Jan 2005.

<http://www.bspp.org.uk/ndr/jan2005/2005-05.asp>

Leaves were collected from a cotton (_Gossypium barbadense_) stock plant "MLC" found at the University of Agricultural Sciences, Hebbal, Bangalore, showing mild leaf curl, some vein thickening and enations.

The infection originated from a naturally-infected _G. barbadense_ at this site and was maintained by successive _Bemisia tabaci_ inoculations. Sequence data generated from cloning PCR products amplified from total MLC-leaf DNA using begomovirus-specific primers enabled the design of primers to amplify the complete DNA-A molecule.

The sequence of the cloned complete DNA-A PCR product (2751 nt, AY705380) had 84-85 percent nucleotide identity with Cotton leaf curl Multan virus (CLCuMV, AJ002447, AJ002459), followed by 83.4 percent with Malvastrum yellow vein virus (MYVV, AJ457824). A phylogenetic tree was constructed to show the relationship of the MLC virus to other Asian begomoviruses present in GenBank. Nucleotide identities of individual genes suggest that the DNA-A sequenced is of recombinant origin.

A DNA-B component could not be amplified from MLC-leaf total DNA using degenerate DNA-B specific primers. A DNA-b component was amplified using Briddon et al. (2003) primers and its sequence (AY705381) shared most nucleotide identity (approximately 84 percent) with DNA-b molecules from cotton and hibiscus in Pakistan (Acc. No. AJ292769 and AJ297908).

The conserved C1 gene of the DNA-b molecule showed highest nucleotide identities (89.1-89.6 percent) and amino acid similarity (80.5-81.4 percent) with similar sequences from tomato (AJ316035) and cotton _G. hirsutum_ (AJ298903) from Pakistan.

Cotton leaf curl diseases in Pakistan and northern India are associated with 5 distinct begomovirus species, which all share a similar DNA-b. Sequence data suggest MLC has not originated from such regions, but is associated with a new begomovirus and distinct DNA-b component.

Based on DNA-A sequence taxonomic guidelines, the virus from MLC is a new begomovirus species for which the name Cotton leaf curl Bangalore virus is proposed.

References:

Briddon RW, Bull SE, Amin I, Idris AM, Mansoor S, Bedford ID, Dhawan P, Rishi N, Siwatch SS, Abdel-Salam AM, Brown JK, Zafar Y, Markham PG, 2003. Diversity of DNA-b, a satellite molecule associated with some monopartite
begomoviruses. Virology 312, 106-21.

Fauquet CM, Bisaro DM, Briddon RW, Brown JK, Harrison BD, Rybicki EY, Stenger DC, Stanley J, 2003. Revision of taxonomic criteria for species demarcation in the family Geminiviridae, and an updated list of begomovirus species. Archives of Virology 148, 405-421.

Mansoor S, Briddon RW, Bull SE, Bedford ID, Bashir A, Hussain M, Saeed M, Zafar Y, Malik KA, Fauquet C, Markham PG, 2003. Cotton leaf curl disease is associated with multiple monopartite begomoviruses supported by single DNA-b. Archives of Virology 148, 1969-1986.

Rojas MR, Gilbertson RL, Russell DR, Maxwell DP, 1993. Use of degenerate primers in the polymerase chain reaction to detect whitefly transmitted geminiviruses. Plant Disease 77, 340-347.

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[The link to the original piece contains all of the text and graphics and is located just under the list of authors.

This piece illustrates the continual evolution of new cotton virus strains and species. There are at least 5 strains/isolates of CLCuV known, most of which are reported from Pakistan and western India. Cotton leaf curl Gezira virus is the more cosmopolitan strain, occurring in Egypt and Sudan, and is known to be present in Central Africa, Chad, Nigeria, Togo and West Africa. Cotton leaf curl disease (CLuCD) is a serious disease of cotton and several other malvaceous plant species that is transmitted by the whitefly _Bemisia tabaci_. Control of CLCuD is mainly based on insecticide treatments against _Bemisia tabaci_. Roguing, particularly of ratoon cotton from the previous seasons crop, is recommended but appears to have little affect in reducing disease incidence. Resistant cotton cultivars have been introduced that were developed by conventional breeding and selection. However, recent reports have suggested that the virus complex has overcome the resistance.

Do any of our readers know whether yields of cotton seed oil are affected by these viruses? Let me know, please.

Links:
<http://ag.arizona.edu/~zxiong/cotgemi.html>
<http://gemini.biosci.arizona.edu/viruses/clcuv-mw/index.htm>
<http://gemini.biosci.arizona.edu/viruses/clcurv/index.htm>
<http://gemini.biosci.arizona.edu/viruses/clcumv/index.html>
<http://gemini.biosci.arizona.edu/viruses/clcukv/index.html>
<http://gemini.biosci.arizona.edu/viruses/clcugv/index.htm>
<http://gemini.biosci.arizona.edu/viruses/clcuav/index.html>
<http://www.bspp.org.uk/publications/pathprofiles/pathprofile34.htm>
- Mod.DH]