Based on putative secondary structures for the 3 0 NTRs of CMV and TAV, models have been proposed to account for the generation of some of the other recombination products previously observed to occur between CMV and TAV (33, 38) . These models are based on template switching of the viral replicase on a stem-loop structure present in the (À) RNA 3 (L1/L2 in Figure 7 ) that may be the promoter for the synthesis of subgenomic RNAs 3B and 5 (33, 38) . Similar structures can be used to explain the various recombinant products obtained here and the effect of the 163-nt repeats and the single G to A substitution on the recombination event.