Submitted to: Virus Genes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/17/2006
Publication Date: 1/1/2007
Citation: Ling, K. 2007. Molecular characterization of two Pepino mosaic virus variants from imported tomato seed reveals high levels of sequence identity between Chilean and U.S. isolates. Virus Genes. 34:1-8. Interpretive Summary: Pepino mosaic virus (PepMV) has caused an emerging disease in greenhouse tomato production in Europe, North America, and South America since 1999. The seed borne nature of PepMV in tomato seed may have contributed to the spread of the disease across several continents. PepMV is very contagious and can spread rapidly through mechanical contacts to plants by contaminated hands or tools. In this study, we were interested in studying the possible origin and source of virus inoculum to the two US isolates (US1 and US2). Two Chilean isolates of PepMV (Ch1 and Ch2) were cloned and their genomes sequenced. Comparisons between different PepMV isolates around the world revealed high levels of nucleotide sequence identity between Chilean (Ch1 and Ch2) and US (US1 and US2) isolates, with 99% between PepMV Ch1 and US1, and 91% between Ch2 and US2. The close relationship between the Chilean and the US isolates suggests that US1 and US2 were likely recent introductions from Chile to the United States. This study provided some clues as to the possible origin of US isolates.
Technical Abstract: Two isolates (Ch1 and Ch2) of pepino mosaic virus (PepMV) were obtained from an imported tomato seed lot originally produced in Chile. Their RNA genomes have been cloned and sequenced. Excluding poly(A) tails, the genomes of PepMV Ch1 and Ch2 were 6,414 nt and 6,412 nt, respectively. Pairwise comparisons of PepMV Ch1 or Ch2 genomes with other PepMV isolates showed that the highest nucleotide sequence identity was with two US isolates, 98.7% between PepMV Ch1 and US1, and 90.7% between Ch2 and US2. In contrast, PepMV Ch1 and Ch2 were the most divergent (78%). These Chilean isolates shared only 78-86% nucleotide identity to the other seven PepMV tomato isolate sequences in GenBank. The high level of sequence identity between Chilean and US isolates suggests a common origin.