Abstract

Of about 14 different viruses or virus-like diseases reported to occur in Ribes species, only Blackcurrant reversion (BRD [blackcurrant reversion associated virus]) and Gooseberry vein banding (GVBD) diseases appear to be of international significance economically. BRD, that affects black currant and red currant, is the most important because of the severity of the crop loss it induces and its worldwide occurrence (except in the Americas and Australia). Additionally, effective control of BRD is very difficult because the causal virus is transmitted by microscopic eriophyid mite vectors that feed within buds, and disease symptoms may take up to 3 years to develop in plants. Although intractable to study for more than 50 years, the causal agent of BRD, blackcurrant reversion virus (BRV), has now been characterised and a rapid means of detecting it in infected Ribes plants was developed. The sensitivity of detection was improved further. The control of the disease is difficult using acaricides to kill mite vectors and roguing infected plants, and this not very effective once BRD incidence in crops reaches >5%. The most promising means of controlling BRD is by incorporating genes for resistance to eriophyid mite vectors and/or to BRV. GVBD occurs commonly in Ribes species worldwide and, under experimental conditions, is known to decrease growth and yield in gooseberry and red currant; symptoms in blackcurrant and red currant are less obvious than in gooseberry. The causal agent(s) is transmitted by several aphid species that colonize Ribes. Recent studies have identified and characterised a putative badnavirus, gooseberry vein banding associated virus, that is 100% correlated with the disease. A sensitive and rapid assay for this virus in Ribes was developed. Current control of GVBD depends on planting virus tested stock plants, roguing infected plants and controlling aphid infestations with aphicides.