Different variants of the satellite RNA of groundnut rosette virus are responsible for the chlorotic and green forms of groundnut rosette disease*

Abstract

Groundnut plants with symptoms of rosette disease contain groundnut rosette virus (GRV), but GRV is transmitted by Aphis craccivora only from plants that also contain groundnut rosette assistor virus (GRAV). Two main forms of rosette disease are recognised, 'chlorotic rosette' and 'green rosette'. GRV cultures invariably possess a satellite RNA and this is the major cause of rosette symptoms: satellite-free isolates derived from GRV cultures from Nigerian plants with chlorotic or green rosette, or from Malawian plants with chlorotic rosette, induced no symptoms, or only transient mild mottle or interveinal yellowing, in groundnut. When the satellite RNA species from GRV cultures from Nigerian green or Malawian chlorotic rosette were reintroduced into the three satellite-free isolates in homologous and heterologous combinations, the ability to induce rosette symptoms was restored and the type of rosette induced was that of the cultures from which the satellite RNA was derived. Thus different forms of the satellite are responsible for the different forms of rosette disease. Other forms of the satellite induce only mild chlorosis or mottle symptoms in groundnut. Individual plants may contain more than one form of the satellite, and variations in their relative predominance are suggested to account for the variable symptoms (ranging from overall yellowing to mosaic) seen in some plants graft-inoculated with chlorotic rosette.

Molecular biology of umbraviruses: phantom warriors

“…Experiments on replication in protoplasts have not been done, but absolute dependence of the replication of the satellite RNAs on an umbravirus helper has been demonstrated in whole plants (Murant et al, 1988;Murant & Kumar, 1990;Demler et al, 1994), although it does not have to be the natural helper (Demler et al, 1996a). Thus, the helper virus replicase is presumably involved in replication of satellite RNA.…”

“…In the case of GRV, satellite RNA is found in all naturally occurring isolates, and is primarily responsible for the symptoms of groundnut rosette disease (Murant et al, 1988;Murant & Kumar, 1990). GRV satellite RNA is an ssRNA of 895-903 nt, which relies on GRV for its replication (Blok et al, 1994) and, more unusually, is also required for the Groundnut rosette assistor virus (GRAV)-dependent aphid transmission of GRV (Murant, 1990).…”

Monoclonal antibodies to double-stranded RNA as probes of RNA structure in crude nucleic acid extracts

“…Two of the major dsRNAs, dsRNA-1 (4.6 kbp) and dsRNA-2 (1.3 kbp) both hybridize to the genomic ssRNA and probably represent its replicative forms (10). The highly abundant dsRNA-3 (900 bp) seems to be a satellite RNA which is probably responsible for the symptoms of groundnut rosette (10,11). By using dsRNA specific MAB we detected the same dsRNA species in aqueous leaf extracts as those described in the literature (10) and determined the thermal denaturation profile of dsRNA-3.…”

Trans-acting untranslated elements of groundnut rosette virus satellite RNA are involved in symptom production.

“…GRV isolates that lack the satellite induce no symptoms or only a transient mild mottle when inoculated to groundnut (Murant et al, 1988). Moreover, different variants of the sat-RNA are responsible for the different forms of rosette disease, such as green rosette and chlorotic rosette (Murant & Kumar, 1990). The sequences of 10 variants of GRV sat-RNA have been determined (Blok et al, 1994).…”