An onion isolate of tobacco rattle virus: reactivity with an antiserum to Hypochoeris mosaic virus, a putative furovirus, and molecular analysis of its RNA 2.

A tubular virus from onion was found to react with an antiserum to Hypochoeris mosaic virus (HyMV), a putative furovirus. Sequence analysis of its genomic RNAs and further serological tests, however, indicated it to be a tobravirus rather than a furovirus. The reactivity of the HyMV antiserum with several isolates of tobacco rattle virus (TRV) suggests that HyMV itself may be a tobravirus. The deduced amino acid sequences of the putative proteins encoded on RNA 2 of the onion virus isolate (ON) suggest close evolutionary relationships to the TRV isolate TCM from tulip. However, RNA 2 of the ON isolate contains a shorter RNA 1-like sequence on its 3'-end and an additional small ORF upstream of its RNA 1-like part. The sequence of its 315 5'-terminal nucleotides is more similar to that of RNA 2 of the PLB isolate from potato than to that of TCM RNA 2.