A new begomovirus isolated from Gossypium barbadense in southern India

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 (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% identity 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-β component was amplified using primers described by Briddon et al. (2003) and its sequence (AY705381) shared most nucleotide identity (≈ 84%) with DNA-β molecules from cotton and hibiscus in Pakistan (accession nos AJ292769 and AJ297908). The conserved C1 gene of the DNA-β 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, Gossypium 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-β (Mansoor et al., 2003). Sequence data suggest that MLC symptoms have not originated from such regions, but are associated with a new begomovirus and distinct DNA-β component. Based on DNA-A sequence taxonomic guidelines (Fauquet et al., 2003), the virus from G. barbadense‘MLC’ is a new begomovirus species for which the name Cotton leaf curl Bangalore virus is proposed. This research was funded by the UK Department for International Development (project R8247, Crop Protection Programme).