The TAV RNA 3 sequence in the recombinant RNA 3 retained the first repeat [in order of 5 0 to 3 0 on the (+) sense strand] of two 163-nt tandem repeats (39) , but lacked the second one, which originally was present in the TAV RNA 3 inoculum. The difference between the two 163-nt repeats is an A at position 1966 in the first repeat, with a G at the corresponding position (2129) in the second 163-nt repeat ( Figure 3A left) (39) . The repeated sequences showed no difference in viral pathogenicity when only one or the other was present (39) . The 3 0 terminal 310 nt of the recombinant RNA 3 was not only the same as the 310 terminal nucleotides of Q-CMV RNA 1, but was also the same length as Q-CMV RNA 5. Q-CMV RNA 5 is a mixture of subgenomic RNAs derived from the 3 0 terminal NTR of RNAs 1, 2 and 3 [(48); our unpublished data]. The level of RNA 5 has a strong effect on the severity of symptoms; the presence of more RNA 5 in the plants results in less severe symptoms (our unpublished data).