Occurrence of Sweet potato leaf curl virus in Sicily.

The Ipomoea -infecting begomoviruses are an evolutionary curiosity. Two such viruses have been identified: Sweet potato leaf curl virus (SPLCV; Lotrakul & Valverde, 1999) and Sweet potato leaf curl Georgia virus (SPLCGV), originating from the USA (SPLCV and SPLCGV) and Spain [SPLCV-Ipo, previously known as Ipomoea yellow vein virus (Banks et al ., 1999) but now recognized as a distinct strain of SPLCV]. These viruses are monopartite (no DNA B or DNA β component has been identified for any of the viruses), have a genome organization typical of Old World begomoviruses, and are distinct from all other begomoviruses. Cuttings of Ipomoea indica (Convolvulaceae) showing yellow vein symptoms were collected in the vicinity of Catania, Sicily in 1999. A full-length clone of the begomovirus associated with the disease was produced by PCR-mediated amplification with a pair of primers abutting at their 5 ′ ends and spanning (for SPLCV-Ipo) nucleotides 697–758 (virion-sense primer 5 ′ -GGATCCGCTGAACTTTGGCCAGATCTTCACTATG-3 ′ ; complementary-sense primer 5 ′ -GGATCCTTATTGGGCCTTGTATCACGAATCAACC-3 ′ ). These were designed to the sequence of SPLCV-Ipo (EMBL accession number AJ132548) and span a unique Bam HI restriction endonuclease site. The full-length PCR product was cloned into the T-Easy vector (Promega) and the sequence of a single clone was determined. This sequence (accession no. AJ586885) is 2830 nucleotides long and shows the arrangement of genes typical of the genomes (or DNA A components) of Old World begomoviruses. The virus is closely related to other begomoviruses isolated from Ipomoea spp., including SPLCGV (84·2% nucleotide sequence identity), SPLCV (89·9%) and SPLCV-Ipo (90·9%), with which it clusters in phylogenetic analyses. We conclude that the isolate originating from Sicily is a strain of SPLCV which is provisionally designated SPLCV-[Sicily]. The occurrence of this begomovirus species in Sicily indicates that its geographical range extends further across the Mediterranean basin than previously identified.