First report of Cilevirus associated with green ringspot on senescent hibiscus leaves in Tampa, Florida

Authors: Roy, Avijit; Stone, Andrew; MELZER, M - University Of Hawaii; Hartung, John; MAVRODIEVA, VESELA - Animal And Plant Health Inspection Service (APHIS); NAKHLA, MARK - Animal And Plant Health Inspection Service (APHIS); BRLANSKY, RONALD - University Of Florida; Schneider, William

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2017
Publication Date: 12/20/2017
Citation: Roy, A., Stone, A.L., Melzer, M.J., Hartung, J.S., Mavrodieva, V., Nakhla, M.K., Brlansky, R.H., Schneider, W.L. 2017. First report of Cilevirus associated with green ringspot on senescent hibiscus leaves in Tampa, Florida. Plant Disease. http://doi.org/10.1094/PDIS-11-17-1699-PDN.
DOI: https://doi.org/10.1094/PDIS-11-17-1699-PDN

Interpretive Summary: A group of viruses called Cileviruses cause a very important disease of citrus in South America, called leprosis. These viruses have not been found in the mainland of the United States, though a hibiscus-infecting member of the group was reported previously from Hawaii. Cileviruses share many common biological features and are all transmitted by a group of mites that are known to feed on different plants, including citrus. We observed symptoms on hibiscus leaves in Tampa, Florida that looked very much like those observed on hibiscus in Hawaii. Samples were taken to the laboratory for analysis and a hibiscus-infecting strain of Cilevirus was unambiguously identified. This virus is very closely related to the hibiscus-infecting virus in Hawaii and to a Cilevirus from Colombia that causes a very serious disease of sweet orange. This is the first time this virus has been reported in Florida. Symptoms have not been reported in citrus in Florida, and it is not known whether the mite vector that transmitted the virus to hibiscus will also feed on citrus in Florida. Citrus growers in Florida will now have to be on the alert for a new disease problem.

Technical Abstract: The genus Cilevirus includes plant and mite associated viruses with single stranded and positive sense bipartite genomes. The type member of the genus is Citrus leprosis virus, which causes an important disease of citrus in South America, but is not known to occur in Florida. Symptoms of the disease begin with green ringspots. Green ringspot symptoms in senescing Hibiscus (H. rosa-sinensis) leaves were observed in Tampa, Florida, in August, 2016. Both symptomatic and asymptomatic leaves were collected from five hibiscus plants. Total RNA was isolated and tested by RT-PCR using primers specific for different isolates of citrus leprosis and Hibiscus green spot viruses. In addition, a generic Cilevirus forward primer and HiCV specific reverse primer were designed and utilized in the RT-PCR assays. Primers specific for CiLV-C, -C2 and HGSV-2 failed to produce any amplicons from symptomatic hibiscus samples. The HiCV genome specific RT-PCR assays yielded a 1447 nt amplicon that encoded part of the RNA dependent RNA polymerase and complete coat protein genes of a Cilevirus. The amplicon was cloned and sequenced. BLAST analysis of the amplicon sequence showed nucleotide sequence identity of 95% and a close phylogenetic relationship with the HiCV isolate from Hawaii (KC626783) confirming the identity of the virus as HiCV. The amplicon sequence of the new Cilevirus from Tampa has been deposited in GenBank (Accession: MG021325). A small RNA library was constructed for Illumina next generation sequencing assay using RT-PCR positive RNA. Potential virus reads (21-24 nt) were identified following a subtractive approach to confirm the presence of HiCV genome sequence in the symptomatic hibiscus leaves. Blast results of several contigs showed 92-98% nucleotide identity with HiCV Hawaiian isolate. Except for HiCV no other virus sequence was detected. To our knowledge, this is the first report of HiCV in Florida and the mainland United States. There is no report of HiCV infection on citrus, but the likely vector of HiCV, (Brevipalpus spp.), is widespread in Florida, and the closely related virus CiLV-C2 causes destructive citrus leprosis disease in Colombia. Because the symptoms of CiLV-C2 observed on hibiscus in Colombia were not typical of leprosis symptoms reported in sweet orange, further studies are necessary to determine the incidence and distribution of HiCV in other citrus growing countries and its potential effects on citrus.