Occurrence and genetic diversity of Blackcurrant reversion virus found on various cultivated and wild Ribes in Latvia

A large‐scale survey was carried out to assess the occurrence, natural host range and genetic diversity of Blackcurrant reversion virus (BRV) in cultivated and wild Ribes in Latvia using RT‐PCR and sequence analyses of 3′ NTR of BRV RNA2. The virus was detected in all surveyed habitats in most of the studied Ribes, except gooseberries, Ribes sanguineum, Ribes laxiflorum and crossbreeds between blackcurrants and gooseberries. The overall occurrence of BRV was 27%, although it varied significantly among the surveyed Ribes habitats, exceeding 40% in home gardens and germplasm collections. Among cultivated Ribes, blackcurrants were the most infected and BRV was detected in all commonly grown cultivars. The virus was detected for the first time in Ribes aureum, Ribes fragrans, Ribes nigrum var. pauciflorum and Ribes fasciculatum var. chinense. The sequence identities of the studied fragments of RNA2 3′ NTR varied from 92.8% to 99.7% among 26 BRV isolates from various cultivated, ornamental and wild hosts from Latvia and from 91.1% to 97.1% when they were compared with 27 corresponding sequences from GenBank. Phylogenetic analyses revealed that the major clustering of isolates was not related to host, origin or symptoms. Grouping of BRV isolates based on host or location was identified within the phylogenetic subclusters. Several well‐supported clades were formed within the subclusters, including a group of BRV isolates from redcurrants that had unique nucleotide substitutions. Five putative recombinants were identified for the first time among BRV isolates from Latvia, Finland, Scotland and the Czech Republic.