First report of Rose rosette virus associated with rose rosette disease infecting roses in Kern County, California

Authors: AL RWAHNIH, MAHER - University Of California, Davis; KARLIK, JOHN - University Of California, Davis; DIAZ-LARA, ALFREDO - University Of California, Davis; ONG, KEVIN - Texas A&M University; Mollov, Dimitre; HAVILAND, DAVID - University Of California, Davis; GOLINO, DEBORAH - University Of California, Davis

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2018
Publication Date: 9/23/2018
Citation: Al Rwahnih, M., Karlik, J., Diaz-Lara, A., Ong, K., Mollov, D.S., Haviland, D., Golino, D. 2018. First report of Rose rosette virus associated with rose rosette disease infecting roses in Kern County, California. Plant Disease. https://doi.org/10.1094/PDIS-07-18-1203-PDN.
DOI: https://doi.org/10.1094/PDIS-07-18-1203-PDN

Interpretive Summary: Roses are widely used as ornamental landscape plants and for cut flower production. Two rose plants obtained from a commercial nursery and three rose plants obtained from homeowner gardens, all in Kern County, CA, were observed with rose rosette disease symptoms. These plants tested positive for Rose rosette virus (RRV). RRV is known to be spread by an eriophyid mite, which was found on infected plants. This is the first report of RRV infecting roses in California. This information will be useful to plant diagnosticians and regulatory agencies, as well as the ornamental and landscape industries.

Technical Abstract: Rose rosette disease (RRD) affecting rose (Rosa spp.) is an endemic disorder in the United States (U.S.). RRD was first described in the western U.S. and Canada in the early 1940s (Conners 1941) and is now widely distributed in the eastern U.S. Typical RRD symptoms include excessive lateral shoot growth and thorniness, witch's broom, leaf proliferation and malformation, mosaic, red pigmentation, and eventual plant decline and death. RRD is caused by the negative-sense RNA virus, Rose rosette virus (RRV), which is vectored by the eriophyid mite (Phyllocoptes fructiphilus Keifer) (Laney et al. 2011; Di Bello et al. 2015). California (CA) is one of the main producers of roses in the U.S. with a wholesale value of $17.6 million in 2016 (NASS 2016). In August 2017, symptoms suggestive of RRD were observed on two roses (cvs. Veterans’ Honor and Brilliant Pink Iceberg) in a commercial nursery in Wasco, CA. A total of 415 samples, representing many rose cultivars were collected from the nursery. Total RNA was extracted from leaf petioles using the MagMAX™-96 viral RNA isolation kit (Thermo Fisher Scientific, U.S.) and tested for RRV using a modified real-time reverse transcription quantitative PCR (RT-qPCR) assay developed by Dobhal et al. (2016). Only the two symptomatic plants were positive for RRV. Plants were also microscopically examined and the P. fructiphilus mite was observed and recovered from several plants throughout the nursery. In June 2018, a separate incident occurred where three garden roses (unknown cultivars) planted in two neighboring homes in Bakersfield, CA, ca. 50 km from the 2017 finds, were identified with RRV-like symptoms. Leaves from all three plants tested positive for RRV by RT-qPCR and were also infested with P. fructiphilus mites. To confirm these results, total nucleic acid was extracted from leaves that had been collected and stored (-80 °C) from all five symptomatic plants and used for cDNA library construction after a ribosomal RNA depletion step (TruSeq Stranded Total RNA with RiboZero Plant kit, Illumina, San Diego, CA). High-throughput sequencing (HTS) was performed on the Illumina NextSeq 500 platform, generating between 15-41 million 75 nt single-end raw data reads per sample. Analysis of the HTS reads identified nearly complete sequences of the seven RRV genome segments from all five samples. The RRV genomes from the two nursery plants sampled in 2017 were 100% identical to one another. The RRV genomes from the three homeowner plants sampled in 2018 were 100% identical to each other, but not to the nursery samples. These results suggest that the samples from these two locations are likely two separate introductions of RRV. Two genomic sequences, one from each location, were submitted to GenBank under the accession numbers MH581213-26. Sequences from the two locations share 98% nucleotide identity to the NCBI reference RRV RNA3 (NC_015300) and RNA7 (NC_034981) and 99% identity to the NCBI reference RRV RNA1-2 (NC_015298-99) and RNA4-6 (NC_015301, NC_034979-80). To our knowledge, this is the first detection of RRV causing RRD in CA. A larger scale survey of commercial fields and landscape gardens is needed to determine the prevalence of RRV and its P. fructiphilus vector in CA.