Complete nucleotide sequence of a highly divergent cherry-associated luteovirus (ChALV) isolate from peach in South Korea

The Expanding Menagerie of Prunus-Infecting Luteoviruses

Members of the genus Luteovirus are responsible for economically destructive plant diseases worldwide. Over the past few years, three luteoviruses infecting Prunus trees have been characterized. However, the biological properties, prevalence, and genetic diversity of those viruses have not yet been studied. High-throughput sequencing of samples of various wild, cultivated, and ornamental Prunus species enabled the identification of four novel species in the genus Luteovirus for which we obtained complete or nearly complete genomes. Additionally, we identified another new putative species recovered from Sequence Read Archive data. Furthermore, we conducted a survey on peach-infecting luteoviruses in eight European countries. Analyses of 350 leaf samples collected from germplasm, production orchards, and private gardens showed that peach-associated luteovirus (PaLV), nectarine stem pitting-associated virus (NSPaV), and a novel luteovirus, peach-associated luteovirus 2 (PaLV2), are present in all countries; the most prevalent virus was NSPaV, followed by PaLV. The genetic diversity of these viruses was also analyzed. Moreover, the biological indexing on GF305 peach indicator plants demonstrated that PaLV and PaLV2, like NSPaV, are transmitted by graft at relatively low rates. No clear viral symptoms have been observed in either graft-inoculated GF305 indicators or different peach tree varieties observed in an orchard. The data generated during this study provide a broader overview of the genetic diversity, geographical distribution, and prevalence of peach-infecting luteoviruses and suggest that these viruses are likely asymptomatic in peach under most circumstances.

Is There a "Biological Desert" With the Discovery of New Plant Viruses? A Retrospective Analysis for New Fruit Tree Viruses

High throughput sequencing technologies accelerated the pace of discovery and identification of new viral species. Nevertheless, biological characterization of a new virus is a complex and long process, which can hardly follow the current pace of virus discovery. This review has analyzed 78 publications of new viruses and viroids discovered from 32 fruit tree species since 2011. The scientific biological information useful for a pest risk assessment and published together with the discovery of a new fruit tree virus or viroid has been analyzed. In addition, the 933 publications citing at least one of these original publications were reviewed, focusing on the biology-related information provided. In the original publications, the scientific information provided was the development of a detection test (94%), whole-genome sequence including UTRs (92%), local and large-scale epidemiological surveys (68%), infectivity and indicators experiments (50%), association with symptoms (25%), host range infection (23%), and natural vector identification (8%). The publication of a new virus is cited 2.8 times per year on average. Only 18% of the citations reported information on the biology or geographical repartition of the new viruses. These citing publications improved the new virus characterization by identifying the virus in a new country or continent, determining a new host, developing a new diagnostic test, studying genome or gene diversity, or by studying the transmission. Based on the gathered scientific information on the virus biology, the fulfillment of a recently proposed framework has been evaluated. A baseline prioritization approach for publishing a new plant virus is proposed for proper assessment of the potential risks caused by a newly identified fruit tree virus.

Identification and characterization of a novel rhabdovirus infecting peach in China

A novel negative-sense, single-stranded (ss) RNA virus was identified in peach trees by high-throughput sequencing, and named peach virus 1 (PeV1). The genome of PeV1 consists of 13,949 nucleotides (nt), and its organization is typical of rhabdoviruses with six open reading frames (ORFs) encoding deduced proteins N-P-P3-M-G-L on the antisense strand. These ORFs are separated by highly conserved intergenic sequences and flanked by complementary 3'-leader and 5'-trailer sequences. PeV1 shared highest complete genome (41.9%), N amino acid (43.6%), G amino acid (41.0%), and L amino acid (42.7%) identities with viruses which belong to the genus Alphanucleorhabdovirus, suggesting it may belong to a new species. This was further supported by phylogenetic analyses using amino acid sequences of N, G, and L proteins, in which this virus is always clustered with alphanucleorhabdoviruses. Collectively, results suggest that PeV1 is a member of a new alphanucleorhabdovirus species. Moreover, bioassays revealed that it could be transmitted through grafting. The findings expand our knowledge of peach-infecting viruses and alphanucleorhabdoviruses.

Recent Advances on Detection and Characterization of Fruit Tree Viruses Using High-Throughput Sequencing Technologies

Perennial crops, such as fruit trees, are infected by many viruses, which are transmitted through vegetative propagation and grafting of infected plant material. Some of these pathogens cause severe crop losses and often reduce the productive life of the orchards. Detection and characterization of these agents in fruit trees is challenging, however, during the last years, the wide application of high-throughput sequencing (HTS) technologies has significantly facilitated this task. In this review, we present recent advances in the discovery, detection, and characterization of fruit tree viruses and virus-like agents accomplished by HTS approaches. A high number of new viruses have been described in the last 5 years, some of them exhibiting novel genomic features that have led to the proposal of the creation of new genera, and the revision of the current virus taxonomy status. Interestingly, several of the newly identified viruses belong to virus genera previously unknown to infect fruit tree species (e.g., Fabavirus, Luteovirus) a fact that challenges our perspective of plant viruses in general. Finally, applied methodologies, including the use of different molecules as templates, as well as advantages and disadvantages and future directions of HTS in fruit tree virology are discussed.

Complete Genome Sequence of Nectarine stem pitting-associated virus, Isolated from Prunus persica in Cheongdo County, South Korea

We report here the first complete genome sequence of a South Korean isolate of Nectarine stem pitting-associated virus (NSPaV) from peach and compare it with previously described complete NSPaV genome sequences. The highest whole-genome nucleotide sequence identity was 95.3% with GenBank accession no. KT273409 (NSPaV) from the United States.