First Report of Tomato golden mottle virus on Lycopersicon esculentum and Solanum rostratum in Mexico.

The Rioverde Valley is an important farming area of the San Luis Potosi State in the north-central region of Mexico, where a variety of horticultural crops (i.e., tomato, pepper, cucumber, and watermelon) are annually cultivated. In the summer of 2005, a number of plants exhibiting a variety of symptoms, including leaf yellowing, curling, and stunted growth, were observed in several tomato (Lycopersicon esculentum L.) fields. The presence of whiteflies (Bemisia tabaci Genn.) and symptoms seemed to suggest a begomoviral etiology. Leaves of 12 symptomatic tomato plants and seven plants of the weed Solanum rostratum (Dunal) growing into the same area were collected in July and September from several fields throughout the Rioverde area and assessed for the presence of begomoviruses (genus Begomovirus, family Geminiviridae) by PCR using the degenerate primers prRepDGR (CCTCCTCTAGCASWTCTNCCGTC), SL2050 (2), and prC889 (3). Amplicons of 1.4 kb were derived from viral DNA-A present in all examined S. rostratum and tomato samples, which were cloned into pGEM-T Easy Vector (Promega, Madison, WI) and subsequently analyzed by restriction fragment length polymorphism (RFLP) using MspI and HinfI. Several restriction fragment patterns were observed among the cloned PCR products, hence indicating the occurrence of different begomoviruses in the sampled fields. Sequencing of amplicons derived from one S. rostratum plant revealed the concurrent presence of Tomato severe leaf curl virus (ToSLCV; GenBank Accession No. DQ347946; [2]) and a distinct virus (GenBank Accession No. EF501978) displaying a high sequence identity with Tomato golden mottle virus from Guatemala (ToGMoV-GT94-R2; GenBank Accession No. AF32852). Restriction fragment patterns identical to that of the ToGMoV-like isolate were found in PCR clones from three additional S. rostratum plants and five tomato samples. A set of partially overlapping PCR products of 1.8 and 1.4 kb encompassing the complete DNA-A component of ToGMoV were obtained from one tomato sample by using two pairs of degenerate primers, prRepQGR-rev and prCP70 (1) and prRepDGR and prC889. Amplicons were cloned, sequenced, and compared with viral sequences available in the GenBank database using BlastN and Clustal V alignments (MegAlign, DNASTAR, Madison, WI). The 2,614-bp DNA-A sequence of the Rioverde isolate (GenBank Accession No. DQ520943) displays 93% sequence identity with the Guatemalan isolate of ToGMoV. In addition, a number of B. tabaci specimens of unidentified biotype were collected in one tomato field and total DNA was isolated from them by a modified Dellaporta method. Amplification of viral DNA present in the whiteflies was carried out and the PCR products were cloned and sequenced. One of the begomoviral DNA-A genomes isolated from the whiteflies (GenBank Accession No. EF501976) displayed 99% sequence identity with the virus isolated from plants. Previously, ToGMoV had been found only in Central America ( http://gemini.biosci.arizona.edu/viruses ), but this report considerably expands its known geographical distribution. References: (1) R. De La Torre-Almaraz et al. Plant Dis. 90:378, 2006. (2) J. A. Mauricio-Castillo et al. Plant Dis. 90:1116, 2006. (3) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

First Report of Tomato severe leaf curl virus in México.

San Luis Potosí and Morelos are states situated in the north-central and south-central regions of Mexico, respectively, where a considerable area of agricultural land is occupied by tomato crops. In the summer of 2005, stunting and leaf curling/crumpling symptoms were observed in several tomato (Lycopersicon esculentum L.) fields in Rioverde, San Luis Potosí (Rioverde-SLP). These symptoms and the existence of large populations of whiteflies (Bemisia tabaci Gennadius) in the affected fields suggested a viral etiology. Symptomatic tomato leaves collected during July and September of 2005 from several locations throughout the Rioverde area were assessed for begomovirus presence using polymerase chain reaction (PCR) with three sets of degenerate primers: PAL1v1978/PAR1c496 (3), pCP70for/pCP70rev (1), and two new primers that specifically amplify DNA from viruses of the Squash leaf curl virus (SLCV) lineage, prSL060-for (CGGCGTTRTRRTARACGTCGTC) and prSL150-rev (GCWGCC-AAAGACACCAAYGCCGT). These primers amplify overlapping DNA segments encompassing the complete begomovirus genome A. Amplicons were cloned into pGEM-T easy vector (Promega, Madison, WI) and sequenced. The complete sequence for component A of isolates from two different fields in the Rioverde Valley were assembled and compared with sequences available in the GenBank database using BlastN and the Clustal alignment method (MegAlign, DNASTAR, Madison, WI). The 2588-bp sequence of the Rioverde-SLP1 isolate (Accession No. DQ347946) and the 2594-bp sequence of Rioverde-SLP2 isolate (Accession No. DQ347947) were 97.2% identical. Both field isolates displayed the highest similarity (97.1 and 97.3% nt identity, respectively) with Tomato severe leaf curl virus from Guatemala (ToSLCV-GT96; Accession No. AF130415). Similarity of SLP isolates with Tomato severe leaf curl virus from Nicaragua (Accession Nos. AJ508784 and AJ508785) was significantly lower, 89.9 and 89.7%, respectively. A parallel survey of tomato fields in Xochitepec, Morelos, located 550 km southeast of Rioverde-SLP, was performed during September, 2005. Leaf samples from six plants displaying leaf curling/crumpling symptoms were collected and assessed for begomovirus presence using PCR with the degenerate primers, prC889 (4) and prSL060-for. The 1.4-kb PCR fragments obtained were subsequently analyzed by restriction fragment length polymorphism using MspI and HhaI. Restriction fragment patterns were the same for all amplicons. The 1435-bp DNA A sequence of one isolate from Morelos was determined (Accession No. DQ267157) and compared with sequences available for other begomoviruses using Clustal alignment method. The highest identity (98%) was with ToSLCV-SLP and ToSLCV-GT96 isolates. These data confirm that ToSLCV is infecting tomato in different horticultural regions of Mexico. The presence of this begomovirus has been previously reported in Honduras, Guatemala, and Nicaragua (2). To our knowledge, this is the first report of ToSLCV in Mexico. References: (1) R. De La Torre-Almaraz et al. Plant Dis. 90:378, 2006. (2) M. K. Nakhla et al. Acta Hort. (ISHS) 695:277. Proc. First Int. Symp. on Tomato Diseases. M. T. Momol et al., eds., 2005. (3) M. Rojas et al. Plant Dis. 77:340, 1993. (4) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.