Nucleotide Sequence Homologies among RNA Species of Strains of Tomato Black Ring Virus and Other Nepoviruses

Abstract

SUMMARYNucleotide sequences of the genome RNA species of four strains of tomato black ring virus (TBRV), two each from the Scottish and German serotypes, were compared by hybridization with complementary DNA copies. Within each serotype 90 ~ or more homology was observed between the corresponding RNA species of each pair of strains. Between serotypes greater differences were found, with 30 to 40~ of RNA-1 sequences and only about 10~ of RNA-2 sequences being common to all four strains. Hybridization reactions between RNA species and complementary DNA preparations representing different serotypes proceeded more slowly, and the hybrids melted at lower temperatures than those between homologous combinations, indicating that the apparently conserved sequences are similar, but not identical, in the two serotypes. Satellite RNA species from two TBRV strains in different serotypes had only about a quarter of their sequences in common. Limited nucleotide sequence homology was found between the genome RNA species of TBRV and those of the serologically distantly related grapevine chrome mosaic, cacao necrosis and artichoke Italian latent viruses, but not between TBRV RNA species and those of seven serologically unrelated nepoviruses.

Conservation of the 3'-Terminal Sequences of the Genome RNA Species of Tomato Black Ring Virus

“…In contrast, no homology between the RNA-1 and RNA-2 sequences as a whole could be detected by hybridization techniques (Robinson et aL, 1980;Dodd & Robinson, 1984). However, the regions sequenced amount to less than 3 ~o of each of the RNA molecules, and this degree of homology would be below the sensitivity of the hybridization technique.…”

“…Hybridization experiments did not detect nucleotide sequences common to RNA-1 and RNA-2 of any of four strains of TBRV (Robinson et al, 1980;Robinson, 1982;Dodd & Robinson, 1984). However, homologous sequences comprising less than about 5 ~ of the smaller RNA species might not be detected by this technique, which therefore gives an upper limit of about 250 residues for the homology between RNA-1 and RNA-2.…”

“…Bottom and middle components were separated and RNA-1 and RNA-2 respectively were extracted from them as described by Dodd & Robinson (1984).…”

“…Between serotypes greater differences were found, 30 to 40~ of RNA-1 sequences and only about 10~o of RNA-2 sequences being common to all TBRV strains tested. Limited nucleotide sequence homology was found between the genome RNA species of TBRV and those of serologically distantly related nepoviruses in the same subgroup, such as grapevine chrome mosaic, cacao necrosis and artichoke Italian latent viruses, but not between TBRV RNA species and those of seven serologically unrelated nepoviruses (Dodd & Robinson, 1984).…”

Nucleotide sequence of Hungarian grapevine chrome mosaic nepovirus RNA1

“…GCMV is closely related to tomato black ring virus (TBRV) both serologically (5) and by nucleic acid hybridization (6). Pseudorecombinants have been obtained between GCMV and TBRV (7) and GCMV can cross protect Chenopodium quinoa Wild against the severe apical necrosis caused by the strain S of TBRV (8,9).…”