First molecular identification of a begomovirus isolated from tomato in Madagascar

In April 2001, reduced leaf size, leaf curling, yellowing symptoms, and reduced yield were observed in tomato plants in the southwestern (Toliary, Morondava, Miandrivazo) and northern (Antsiranana) regions of Madagascar. Symptoms were similar to these caused by Tomato yellow leaf curl virus (TYLCV, genus Begomovirus, family Geminiviridae). Large populations of Semisia tabaci (Gennadius) were observed colonizing tomato, other crops, and weeds. Leaf samples were collected from tomato plants from 14 sites located in northern, central, and southern Madagascar. Two plant samples collected near Antsiranana, one sample near Morondava, and one sample near Toliary were positive in triple-antibody sandwich enzyme-linked immunosorbent assay using a begomovirus-specific antibody purchased from ADGEN (Nellies Gates, Auchincruive, Scotland, UK). A 500-bp product was amplified and cloned (2) from two leaf samples collected near Toliary and one near Morondava using a pair of degenerate primers that are expected to amplify a region of the A component of begomoviruses between the intergenic conserved nonanucleotide sequence and the first 200 nucleotides of the coat protein ORF. The sequences corresponding to (he two Toliary samples (GenBank Accession Nos. AJ422123 and AJ422124) and the Morondava sample (GenBank No. AJ422125) showed the most significant alignments (NCBI, BLAST) with begomoviruses, Tobacco leaf curl virus from Zimbabwe (GenBank Accession No. AF 350330) and Tomato leaf curl virus from Tanzania (GenBank Accession No. U73498) with 76 to 77% nucleotide identity (Clustal method, MegAlign, DNASTAR, London) and South African cassava mosaic viruses (SACMV GenBank Accession Nos. AJ422132 and AF155806) and East African cassava mosaic viruses from Malawi (GenBank Accession Nos. AJ006459 and AJ006460) with 74 to 75.5% nucleotide identity. The low nucleotide identity suggests that the begomovirus isolated from tomato in Madagascar is a new species. Since the core region of the coat protein gene is a molecular marker for provisional classification of begomoviruses (1), this region was amplified for the Morondava isolate with degenerate primers. The 519nt core fragment obtained showed the most significant alignments with SACMV (GenBank Accession No. AF329227), Cassava geminivirus from Mozambique (GenBank Accession No. AF329240), and with TYLCV (GenBank Accession Nos. AB014346 and AF105975) with 81 to 82% nucleotide identity. According to the current taxonomic criteria (4), the begomovirus from Madagascar is a new one that is related to begomoviruses from the southern part of Africa and to TYLCV and is provisionally named Tomato yellow leaf curl Morondava virus (TYLCMV). Tomato yellow leaf curl disease was previously described in Madagascar by Reckhaus (3) who presumed that it was caused by TYLCV Although symptoms in the tomato plant from which TYLCMV was isolated were similar to those induced by TYLCV, TYLCV was not detected in our samples. (Texte intégral