A new begomovirus isolated from Gossypium barbadense in Southern India

R.V. Chowda Reddy¹, V. Muniyappa², J. Colvin¹ and S. Seal¹*

¹ Plant, Animal and Human Health Group, Natural Resources Institute, University of Greenwich at Medway, Kent, ME4 4TB, UK
² Department of Plant Pathology, University of Agricultural Sciences, GKVK, Bangalore-560065, India

*s.e.seal@greenwich.ac.uk

Accepted for publication 20/01/05

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 (Fig. 1). 

Figure 1: Vein clearing and leaf curling symptoms visible on stock G. barbadense plant showing mild cotton leaf curl symptoms.

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 (Rojas et al., 1993) 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% nucleotide identity with Cotton leaf curl Multan virus (CLCuMV, AJ002447, AJ002459), followed by 83.4% 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 (Fig. 2). Nucleotide identities of individual genes suggest that the DNA-A sequenced is of recombinant origin.

Figure 2: Neighbour joining tree showing the relationship of Cotton leaf curl Bangalore virus (Acc. No. AY705380; CLCuBV) to selected other full length DNA-A sequences from Asia available from GenBank. Numbers at nodes indicate the bootstrap percentage score out of 1000 replicates. The tree was constructed using ICMV as outgroup and sequence name abbreviations are according to Fauquet et al. (2003), with the exception of sequences ToLCV-Iran (Acc. No. AY297924) and ToLCV-Janti and ToLCBV-Pune, which are unpublished sequences obtained by Chowda Reddy RV.

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 (~84%) 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%) and amino acid similarity (80.5-81.4%) 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 five distinct begomovirus species which all share a similar DNA-b (Mansoor et al., 2003). 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 (Fauquet et al., 2003), the virus from MLC is a new begomovirus species for which the name Cotton leaf curl Bangalore virus is proposed.

Acknowledgement

This research was funded by the UK Department for International Development (project R8247, Crop Protection Programme).

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The British Society for Plant Pathology