First report of tobacco as a natural host of Euphorbia mosaic virus in Cuba

In January 2007, two different symptoms appeared in tobacco plants (Nicotiana tabacum) in a field in the eastern province of Cuba. Foliar yellowing and crinkling symptoms were associated with a novel bipartite begomovirus, Tobacco yellow crinkle virus (Fiallo-Olivé et al., 2009). The other symptoms were downward curling, rugosity and yellow mottle of leaves with reduction in plant height (Fig. 1). These symptoms preclude the use of tobacco leaves for the manufacture of cigarettes, an industry of importance to the economy of Cuba. Six plants with symptoms were selected for analysis and all showed amplification with generic primers for genomic components DNA-A and DNA-B, demonstrating the presence of a bipartite begomovirus (Rojas et al., 1993). Restriction analyses were performed on rolling-circle amplification products using EcoRI, EcoRV HindIII, PstI and XbaI. Restriction fragment patterns were the same for the six samples. DNA-A was cloned with EcoRI and DNA-B with HindIII. Both molecules were sequenced (GenBank Accession Nos. FJ807782 and FJ807783, respectively).

Comparisons with the sequences of begomoviruses available in the databases using the program CLUSTAL V showed the virus to have high levels of nucleotide sequence identity to isolates of Euphorbia mosaic virus (EuMV), with the highest to the components of EuMV-[Jamaica:Wissadula] (98.7% identity for DNA-A [DQ395342] and 96.5% for DNA-B [EU740969]). To all other begomovirus species the levels of identity were less than 89%. Comparisons of the DNA-A and DNA-B sequences showed them to share an approximately 174 nt sequence with high sequence identity (98.3%), a feature of bipartite begomoviruses known as the common region. This indicates that the two sequences mostly likely represent the cognate components of a bipartite begomovirus. These data indicate that the virus identified is an isolate of EuMV. This is the first record of EuMV infecting tobacco and of the occurrence of this species in Cuba. Additional work is now needed to determine the epidemiological risk of the presence of this virus in Cuba. Previously, four bipartite begomovirus have been reported to infect tobacco in Cuba (Fiallo-Olivé et al., 2009; Domínguez et al., 2008). For EuMV there is a natural host, Euphorbia heterophylla (Costa & Bennett, 1950), a weed that occurs in many cropping areas in Cuba that can act as a reservoir and contribute to dissemination of the virus.