Fluorescent in situ hybridization on grapevine and nicotiana tissues infected by viruses A and B

In grapevine, multiple natural infections by vitiviruses are relatively common since mealybug transmission and grafting favours the spread of both Grapevine virus A (GVA) and Grapevine virus B (GVB). The two viruses share a relatively high sequence similarity (average of 50% nucleotide identity on the whole genome). Thus, close or identical replication sites in infected cells may increase the chance of homologous recombination, producing viable chimeric RNAs. Since potential recombination events between low titer virus RNAs in infected grapevines, studied by nested RT-PCR, are difficult to detect, an accurate analysis of virus replication sites is needed. Fluorescent in situ hybridization was designed with oligo-labelled DNA or PCR-amplified fragments of CP genes