First report of Blackcurrant reversion virus in Ribes nigrum germplasm in the United States

Authors: Zurn, Jason; HO, THIEN - University Of Arkansas; Li, Ruhui; Bassil, Nahla; TZANETAKIS, IOANNIS - University Of Arkansas; Martin, Robert; Postman, Joseph

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2019
Publication Date: 3/12/2019
Citation: Zurn, J.D., Ho, T., Li, R., Bassil, N.V., Tzanetakis, I., Martin, R.R., Postman, J.D. 2019. First report of Blackcurrant reversion virus in Ribes nigrum germplasm in the United States. Plant Disease. 103:1051. https://doi.org/10.1094/PDIS-03-18-0526-PDN.
DOI: https://doi.org/10.1094/PDIS-03-18-0526-PDN

Interpretive Summary: Reversion disease in black currants is a devistating disease caused by Blackcurrant reversion virus (BRV). A quarantine has been in place for many years to prevent BRV and the mite which spreads it from entering the United States. In 2016, BRV was detected for the first time in the black currant cultivar Burga during a next generation DNA sequencing experiment at the University of Arkansas. A second test was conducted on 'Burga' as well as 11 other black currants which exhibited suspicious leaf symptoms using reverse transcrition polymerase chain reaction (RT-PCR) to confirm the presence of BRV in Oregon. Four of the 11 black currants tested positive for the disease and subsiquent sequencing of the amplicons produced confirmed the presence of BRV. Three of the four black currants which tested positive have been growing in the United States for more than 20 years. These plants were tested when they entered the country through grafting and were thought to be BRV-free. At the time, this assay was the only tool available for BRV detection and is not sufficient to enforce a BRV quarantine. Future work will focus on trying to identify if any additonal plants are infected in the United States black currant collection. Additonally, plant distribution records will be consulted and recipients of infected plants will be notified.

Technical Abstract: Reversion disease, thought to be caused by the eriophyid mite transmitted Blackcurrant reversion virus (BRV), is the most economically important disease of black currants (Ribes nigrum L.) and can be found nearly everywhere blackcurrants are cultivated except North America and Australia (Jones & McGavin, 2002; Lemmetty et al., 1997; Susi, 2004). BRV causes morphological changes to leaf and flower form and shape, reduced flower bud hairiness, decreased plant vigor, sterility, and increased flower pigmentation (Jones & McGavin, 2002; Susi, 2004). National quarantines have prevented the movement of BRV and its vector, Cecidophyopsis ribis Westwood, into the U.S. The host range is limited to the genus Ribes, and the virus rarely infects species other than R. nigrum. In a virus survey of currant germplasm at the National Clonal Germplasm Repository (NCGR) in Oregon, a significant portion of the BRV genome was detected in the black currant cultivar Burga using Next Generation Sequencing (NGS) in Arkansas. ‘Burga’ had been selected for NGS based on abnormal leaf morphology suggestive of BRV. In 2016, RNA extracted from leaf tissue of ‘Burga’ and 11 other NCGR black currant accessions, several of which also exhibited suspicious leaf symptoms, was assayed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in Oregon for BRV using the iTaq One-Step SYBR green RT-PCR Kit (Bio-Rad Laboratories Inc, Hercules, CA, U.S.A.) and primers and annealing conditions recommended by Dolan et al. (2011) and Jones and McGavin (2002). Four cultivars tested positive for BRV at the USDA-ARS NCGR: ‘Bogatyr’ (PI 556413, from Germany); ‘Burga’ (PI 653058, from France); ‘Minaj Shmyrev’ (PI 617766, from England); and an R. nigrum selection (PI 617781, from France). Amplicons from ‘Bogatyr’ and ‘Burga’ were sequenced and showed >96% identity to the published BRV sequences (GenBank: MH078528-9). The vector, C. ribis, is not known to be present in North America and it is unknown if any mites endemic to North America could serve as vectors. Three of the infected clones have been growing at the NCGR for more than 20 years. These clones had been tested by a graft-bioassay when they entered the country and were thought to be BRV-free. At the time, this assay was the only tool available for BRV detection and is not sufficient to enforce a BRV quarantine. Germplasm from the NCGR Ribes collection has been distributed to nurseries and research programs across North America as part of the National Plant Germplasm System. To ensure there has not been any spread and that other black currant clones in the NCGR collection are free of BRV, all 200 black currant clones in the collection will be tested for BRV. Past distribution records of the four infected cultivars of black currant used to identify where these clones have been shipped and the recipients of these materials will be notified (USDA-NPGS, 2018).