Complete nucleotide sequences of two closely related tobacco rattle virus RNA2s for which previously possibly only deletion/recombination mutants had been described

• Molecular characterisation of the new HaB and HaW strains of tobacco rattle virus.
• Possibly missing genes in previously described TRV isolates from potatoes.
• Differences in the 3′ RNA1-like parts of TRV RNA2s with closely related 5′ parts.

The almost complete nucleotide (nt) sequences lacking only short primer-derived 5′ and 3′ terminal portions were determined for the RNA2s of two closely related tobacco rattle virus (TRV) isolates which were detected in recently infected roots of Nicotiana benthamiana bait plants (isolate HaB) or of field-grown potato plants (isolate HaW), respectively. The sequences of c. 1350 5′ proximal nts in these RNA2s were almost identical to those in four previously described TRV isolates from potatoes in the Netherlands and Poland which had been propagated in tobacco leaves. The RNA2s of the earlier isolates, however, consist of only c. 2000 nts, whereas the HaW and HaB RNA2s comprise more than 4000 nts. In addition to the coat protein gene which is present in the RNA2s of all isolates, the HaW and HaB RNA2s contain two further open reading frames which in the previous isolates were apparently lost either entirely or of which small remnants only were left. The RNA2s of the previously described isolates and of our new ones have different RNA1-related 3′ ends which apparently have been acquired from different supporting RNA1s. After transmission to tobacco leaves HaB RNA2 formed deletion/recombination mutants which – as in the previous isolates – consisted of only c. 2000 nts. They had acquired the 3′ end from their supporting RNA1.