Biological and Genomic Characterization of a Novel Tobamovirus Infecting Hoya spp.

Abstract

Foliar symptoms suggestive of virus infection were observed on the ornamental plant hoya (Hoya spp.; commonly known as waxflower) in Florida. An agent that reacted with commercially available tobamovirus detection reagents was mechanically transmitted to Chenopodium quinoa and Nicotiana benthamiana. Rod-shaped particles ∼300 nm in length and typical of tobamoviruses were observed in partially purified virion preparations by electron microscopy. An experimental host range was determined by mechanical inoculation with virions, and systemic infections were observed in plants in the Asclepiadaceae, Apocynaceae, and Solanaceae families. Some species in the Solanaceae and Chenopodiaceae families allowed virus replication only in inoculated leaves, and were thus only local hosts for the virus. Tested plants in the Amaranthaceae, Apiaceae, Brassicaceae, Cucurbitaceae, Fabaceae, and Malvaceae did not support either local or systemic virus infection. The complete genome for the virus was sequenced and shown to have a typical tobamovirus organization. Comparisons of genome nucleotide sequence and individual gene deduced amino acid sequences indicate that it is a novel tobamovirus sharing the highest level of sequence identity with Streptocarpus flower break virus and members of the Brassicaceae-infecting subgroup of tobamoviruses. The virus, for which the name Hoya chlorotic spot virus (HoCSV) is proposed, was detected in multiple hoya plants from different locations in Florida.

To Be Seen or Not to Be Seen: Latent Infection by Tobamoviruses

“…The virus can replicate and move systemically but does not cause disease [33] No visible symptoms Hibiscus latent Fort Pierce virus [10] Hibiscus latent Singapore virus [8] Tobacco latent virus [62] Brugmansia latent virus [64] Tolerance…”

First report of Chili pepper mild mottle virus in calibrachoa in the United States

“…For further characterisation, total RNA from four calibrachoa samples (two each from two different greenhouses located in two different states) representing four different calibrachoa varieties were selected for additional RT‐PCR testing at USDA‐ARS with degenerate tobamovirus primers. Amplicons of c. 200 bp were observed from all samples with the tob4404v and tob4593 primers (Adkins et al., 2018) designed to amplify a conserved portion of the replicase gene. Similarly, amplicons of c. 800 bp were observed from all samples with the SolACPv and SolACPvc primers (Chellemi et al., 2011) designed to amplify the 3′ terminus of the movement protein gene, the entire coat protein (CP) gene, and part of the 3′ UTR.…”

A new tobamovirus infecting Hoya spp.

“…Resulting amplicons of c. 800 bp were Sanger sequenced in both directions (Microsynth Seqlab, Germany). The sequences showed 69.4% nucleotide (nt) identity to Hoya chlorotic spot virus (HoCSV; KX434725) (Adkins et al , 2018) indicating the presence of a novel tobamovirus, provisionally named Hoya tobamovirus 2 (HoToV2).…”