Structure predictions correlated with evidence for SSSV in TBFV genomes ( Figure 2) . A remarkable drop in SSSV was observed in the SL6 region between positions 209 and 254 of the Vs sequence. The most extreme drop in variability was observed in a window centred on position 221 within the apical stem of SL6. The levels of SSSV within the remainder of the structural protein-encoding region (positions 295-2435) were higher than the upstream portion. Similarly, high levels of SSSV were observed across the non-structural portion of the genome between positions 322 and 2425 (data not shown).