Natural Occurrence of Viruses in Lycopersicon spp. in Ecuador

The Andean region is home of important genetic diversity for the genus Lycopersicon. A survey of three asymptomatic populations of L. hirsutum, 17 of L. parviflorum, 188 of L. pimpinellifolium, and four cultivated populations of L. esculentum was made in nine departments of Ecuador. Samples were analyzed serologically for Tomato spotted wilt virus (TSWV), Tomato mosaic virus (ToMV), Tobacco mosaic virus (TMV), Cucumber mosaic virus (CMV), Potato virus Y (PVY), Potato virus X (PVX), Groundnut ringspot virus (GRSV), Tomato chlorosis spot virus (TCSV), and Pepino mosaic virus (PepMV). Samples positive as determined using double-antibody sandwich enzyme-linked immunosorbent assay (absorbance values three times higher than negative controls) were analyzed using reverse transcription-polymerase chain reaction (RT-PCR) with virus-specific primers. L pimpinellifolium was the only species of the four found to be infected with viruses. In the department of Manabí, ToMV was detected in 15 of 16 plants from one population, but only a single plant was infected with PepMV. In this department, PepMV was also detected in a single-plant population that corresponded to a volunteer plant found in the wild and TSWV was detected in another plant. In Esmeraldas and Guayas, two single-plant populations were found infected with PepMV and CMV, respectively. TMV, PVY, PVX, GRSV, and TCSV were not detected in this survey. Specific primers were selected for ToMV (To1/To2, genome coordinates 3498-3518/4902-4922, AJ417701), PepMV (Pe1/Pe2 genome coordinates 5030-5050/5913-5935, AJ606359), CMV (Cm1/Cm2 genome coordinates 541-561/1756-1779, D00356), and TSWV (Ts1/Ts2 genome coordinates 4078-4101/4738-4769, AF208498). Amplicons of the expected size were obtained using RT-PCR and then cloned and sequenced. DNA fragments of ToMV, PepMV, and TSWV showed identities greater than 99% with respective sequences in the GenBank database. The highest identity of the CMV DNA fragment was 92% with an isolate from Indonesia (AB042292). The occurrence of viruses such as CMV, ToMV, and TSWV in coastal Ecuador was not surprising. However, infected plants were not found among the samples collected in the departments of Azuay, Carchí, El Oro, Imbabura, Loja, and Pichincha in eastern Ecuador. L. chilense, L. chmielewskii, L. parviflorum, and L. peruvianum were previously reported as natural hosts of PepMV in central and southern Peru (2), and the virus was also detected in L. esculentum in Chile (1). Our results show that PepMV now occurs in wild L. pimpinellifolium populations along the Pacific coast of the South American continent and that it must have efficient means of transmission, although no specific vectors have as yet been identified for this virus. To our knowledge, this is the first report of PepMV in Ecuador and L. pimpinellifolium as a natural host of PepMV. References: (1) M. Muñoz et al. Fitopatología 37:67, 2002. (2) S. Soler et al. J. Phytopathol. 150:49, 2002.