Viral reservoir capacity of wild Prunus alternative hosts of plum pox virus through multiple cycles of transmission and dormancy

Plum pox virus (PPV) is a significant pathogen of Prunus worldwide and is known for having a broad experimental host range. Many of these hosts represent epidemiological risks as potential wild viral reservoirs. A comparative study of the PPV reservoir capacity of three commonly found native North American species, western choke cherry (P. virginiana var. demissa), black cherry (P. serotina), and American plum (P. americana) was conducted. Pennsylvania isolates of PPV-D were transmitted from the original host peach (P. persica cv. GF305) to all three species. Viral accumulation and transmission rates to alternative hosts and peach were monitored over the course of five vegetative growth and cold induced dormancy (CID) cycles. The three alternative host species demonstrated differences in their ability to maintain PPV-D and the likelihood of transmission to additional alternative hosts or back transmission to peach. Western choke cherry had low (5.8%) initial infection levels, PPV-D was not transmissible to additional western choke cherry, and transmission of PPV-D from western choke cherry to peach was only possible before the first CID cycle. Black cherry had intermediate initial infection levels (26.6%) but did not maintain high infection levels after repeated CID cycles. Conversely, American plum had a high level (50%) of initial infection that was not significantly different from initial infection in peach (72.2%) and maintained moderate levels (15-25%) of infection and PPV-D transmission to both American plum and peach through all five cycles of CID. Our results indicate that American plum has the greatest potential to act as a reservoir host for Pennsylvania isolates of PPV-D.

Plantago asiatica mosaic virus.

PlAMV was first described from the wild/weedy plant Plantago asiatica in the Russian Far East, and a Nandina mosaic isolate from cultivated Nandina domestica in the USA. PlAMV also naturally infects P. asiatica and Rehmannia glutinosa in the Republic of Korea, and N. domestica, Primula sieboldii, Lilium maximowiczii [Lilium leichtlinii var. maximowiczii] and Viola grypoceras in Japan. PlAMV has also been detected in commercially grown lilies in the Netherlands and elsewhere in Europe, Taiwan, the USA, Republic of Korea, Chile, China, New Zealand, India and Costa Rica. Japanese lily isolates are distinct from 'European-like' lily isolates, suggesting more than one introduction into lilies. Widespread occurrence in cultivated lilies is likely due to international distribution of infected bulbs. Losses of up to 80% have been reported in commercial greenhouse cut-flower production. PlAMV is able to spread readily through soil by uptake (and probably exudation) through the roots and is quite stable in contaminated planting media; no animal vector is known. PlAMV has a wide experimental host range.

Plantago asiatica mosaic virus.

PlAMV was first described from the wild/weedy plant Plantago asiatica in the Russian Far East, and a Nandina mosaic isolate from cultivated Nandina domestica in the USA. PlAMV also naturally infects P. asiatica and Rehmannia glutinosa in the Republic of Korea, and N. domestica, Primula sieboldii, Lilium maximowiczii [Lilium leichtlinii var. maximowiczii] and Viola grypoceras in Japan. PlAMV has also been detected in commercially grown lilies in the Netherlands and elsewhere in Europe, Taiwan, the USA, Republic of Korea, Chile, China, New Zealand, India and Costa Rica. Japanese lily isolates are distinct from 'European-like' lily isolates, suggesting more than one introduction into lilies. Widespread occurrence in cultivated lilies is likely due to international distribution of infected bulbs. Losses of up to 80% have been reported in commercial greenhouse cut-flower production. PlAMV is able to spread readily through soil by uptake (and probably exudation) through the roots and is quite stable in contaminated planting media; no animal vector is known. PlAMV has a wide experimental host range.

Viral Host Range database, an online tool for recording, analyzing and disseminating virus-host interactions

Motivation Viruses are ubiquitous in the living world, and their ability to infect more than one host defines their host range. However, information about which virus infects which host, and about which host is infected by which virus, is not readily available. Results We developed a web-based tool called the Viral Host Range database to record, analyze and disseminate experimental host range data for viruses infecting archaea, bacteria and eukaryotes. Availability The ViralHostRangeDB application is available from https://viralhostrangedb.pasteur.cloud. Its source code is freely available from the Gitlab hub of Institut Pasteur (https://gitlab.pasteur.fr/hub/viralhostrangedb).

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

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.

An Integrated Badnavirus Is Prevalent in Fig Germplasm

Fig mosaic occurs worldwide and is the most common and important viral disease of fig. In the quest to identify the causal agent of the disease, several new viruses have been identified, including a new DNA virus, the subject of this communication. Phylogenetic analysis placed the virus, provisionally named Fig badnavirus-1 (FBV-1), in the genus Badnavirus, family Caulimoviridae. The experimental host range of FBV-1 was evaluated and the virus was mechanically transmitted to several herbaceous hosts. FBV-1 was detected in the National Clonal Germplasm Repository fig collection and additional samples from Arkansas, California, Florida, Michigan, Ohio, Oregon, and South Carolina, suggesting its wide distribution in the United States. Further tests revealed the presence of FBV-1 in seedlings and meristem tissue culture plants. Forty-four isolates were used in a study evaluating the population structure of the virus in the United States. Evidence that FBV-1 is integrated in the fig genome is presented and discussed.