Black currant reversion disease - the probable causal agent, eriophyid mite vectors, epidemiology and prospects for control

Black currant reversion disease and the vector of its causal agent, the bla ck currant gall mite Cecidophyopsis ribis, have been recognised for at leas t 100 years and are the two most damaging organisms of black currant crops world-wide. However, the molecular characterisation of these two organisms has begun to be determined in only the last few years. The probable causal agent of reversion disease, Black currant reversion associated virus (BRAV) , belongs to the genus Nepovirus, has isometric particles c. 28nm in diamet er that contain a single major polypeptide of c. 55 KDa and two polyadenyla ted ssRNA species of 7700 nt and 6400 nt. Some particle preparations also c ontain a satellite ssRNA species of 1432 nt. Using immune-capture RT-PCR an d primers based on the genomic RNA of BRAV, this virus was shown to be clos ely associated with reversion disease. Analysis of Cecidiophyopsis mite rDN A, identified rapidly and unambiguously the three known species on Ribes an d distinguished four new ones. Resistance to the reversion agent and to the gall mite vector has been introduced into black currant and has given effe ctive control of these respective organisms in the field. These findings an d their significance for the ecology, epidemiology and control of variants of these two organisms are reviewed and discussed. (C) 2000 Elsevier Scienc e B.V. All rights reserved.