First report of Tobacco leaf curl Zimbabwe virus affecting tobacco in the Comoros Archipelago

In March 2004, within the Regional Program of Plant Protection, an inventory of plant pathogens was organised in the Comoros Archipelago, located in the northern part of the Mozambique Channel. Symptoms of leaf curling and yellowing (Fig. 1) were observed on tobacco plants in the Grande-Comore Island; the most northern Island of the Archipelago and the closest to the African continent.

Leaf samples from tobacco plants presenting the most severe symptoms, were collected from three different locations: Foumboudzivouni (eastern region), Foumbouni (southeast region) and Simboussa (southern region). Samples were conserved by dehydration and tested for the presence of begomoviruses using polymerase chain reaction (PCR) assays with two sets of degenerate primers designed to amplify part of the coat protein (CP) gene of the DNA A component. The first primer set used (AV494 and AC1048) amplify the approximately 550bp core region of the CP gene (Wyatt & Brown, 1996). The second primer set used (VD360 and CD1266) amplify an approximately 800bp fragment representing more than 90% of the CP gene (Delatte et al., 2005). PCR products of the expected size were obtained with both sets of primers. No PCR products were obtained with degenerate primers designed for begomovirus DNA B or DNA β. PCR products obtained with primers VD360 and CD1266 from one sample each originating from Foumboudzivouni (EMBL accession no. AM156758), Foumbouni (AM156760) and Simboussa (AM156759) were cloned and sequenced. The three sequences showed 97% nucleotide sequence identity (DNAMAN, Lynnon BioSoft). The most significant sequence alignments (NCBI, BLASTn) were 95 to 96% with Tobacco leaf curl Zimbabwe virus (TbLCZV; AF350330) and 83 to 85% with Chayotte yellow mosaic virus (ChaYMV; AJ223191). The 552bp core CP sequences, which are sometimes used to provide provisional identification of begomoviruses (Brown et al., 2001), showed 95 to 97% nucleotide sequence identity with TbLCZV and 83 to 84% with ChaYMV (Fig. 2).

These results demonstrate the presence of TbLCZV on tobacco in the Grande-Comore Island of the Comoros Archipelago. Previous reports have identified the presence of distinct indigenous begomoviruses on tomato in the south west islands of the Indian Ocean (Delatte et al., 2005), but this is the first report of TbLCZV.