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First Report of Sinaloa Tomato Leaf Curl Geminivirus in Costa Rica

In October 1998, geminivirus-like symptoms were widespread in tomato plantings near Turrialba, Costa Rica. Isolates from several fields were experimentally transmitted to tomato seedlings with whiteflies from a Bemisia tabaci (Genn.) colony maintained at CATIE, which resulted in interveinal chlorosis and leaf curling symptoms indistinguishable from those observed in the field. Total DNA was extracted from leaves of 16 of these experimentally inoculated plants and assayed by polymerase chain reaction (PCR) for the presence of begomovirus DNA with the degenerate primers AV324 and AC889 (2) to amplify the core region of the coat protein gene (core Cp). PCR yielded the expected size core Cp fragment (576 bp) from 16 of 16 samples. The core Cp fragments of six samples were cloned and sequenced. A comparison of the core Cp sequences with reference begomovirus sequences indicated all Costa Rican isolates were >95% identical to Sinaloa tomato leaf curl geminivirus reported in 1994 from Sinaloa, Mexico (STLCV-SINALOA). Virus identity was confirmed by multiple sequence alignments of the viral coat protein gene (Cp) and the common region (CR) sequences of A and B components (CR-A and CR-B), respectively, with analogous reference begomovirus sequences. Cp and CRs were obtained by PCR, and amplicons were cloned and sequenced as described (1). The Cp open reading frame (ORF; 756 nucleotides) (AF110515) identified within the A component amplicon shared 92.9% sequence identity with STLCV-SINALOA Cp (AF040635). The CR sequences of the A (AF1150516) and B (AF110517) components (163 nucleotides) shared 98.2% sequence identity with each other, suggesting that they were amplified from the cognate A and B components of the same virus. Further, the CR-A and CR-B components contained the same putative Rep binding site, TGGGGT-AA-TGGGGT, which was also identical to that of STLCV-SINALOA. The mean percent divergences between viral Cp and CR amplicons (n = 6+) ranged from 98 to 100%. Collectively, STLCV-like symptoms in tomato, >92% identity between viral Cp sequences, and identical CR iterons indicate that the Costa Rican tomato virus is STLCV, or a closely related strain. This is the first report of an STLCV-like begomovirus in tomato in Costa Rica (STLCV-CR).

References: (1) A. M. Idris and J. K. Brown. Phytopathology 88:648, 1998. (2) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.