THE SATELLITE RNAS ASSOCIATED WITH THE GROUNDNUT ROSETTE DISEASE COMPLEX AND PEA ENATION MOSAIC-VIRUS - SEQUENCE SIMILARITIES AND ABILITY OF EACH OTHERS HELPER VIRUS TO SUPPORT THEIR REPLICATION

Pea enation mosaic virus (PEMV) and the causal agents of groundnut ros ette disease are diverse examples of disease complexes involving two R NA species, one of which is related to the genomes of luteoviruses and the other to those of umbraviruses. In both complexes, these viral RN A components may be supplemented with satellite RNAs that are dependen t on the umbravirus component for replication and systemic movement, a nd on the luteovirus component for encapsidation and vector transmissi on. Sequence analysis identified regions of similarity between the sat ellites of groundnut rosette virus (GRV) and PEMV, particularly at the 5' and 3' termini and around duplicate sequence repeats present in ea ch satellite RNA. The umbravirus GRV and the umbravirus-like PEMV RNA- 2 were each able to support the replication and systemic spread of hom ologous and heterologous satellites. The presence of the PEMV satellit e in infections with GRV had no effect on symptom expression in Nicoti ana spp. or in Arachis hypogaea. Likewise, in Pisum sativum, the GRV s atellite had no effect on the symptoms induced by PEMV. However, the i ntense yellow blotch symptoms induced in Nicotiana benthamiana by the YB3 GRV satellite in conjunction with GRV were also manifested when PE MV was the helper. Although PEMV RNA-1 was capable of supporting the e ncapsidation and aphid transmission of the GRV satellite, no evidence was obtained that the essential role of the GRV satellite in the aphid transmission of GRV could be supplied by the PEMV satellite. These da ta further strengthen the hypothesis of an evolutionary relationship b etween PEMV and the luteovirus-umbravirus complexes.