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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.