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Special Issue "Viruses in Forest and Urban Trees and Shrubs"

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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Health".

Deadline for manuscript submissions: closed (20 October 2022) | Viewed by 7048

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Special Issue Editors

Dr. Susanne von Bargen

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Guest Editor

Humboldt-Universität zu Berlin, Faculty of Life Sciences, Albrecht Daniel Thaer-Insitute for Agricultural and Horticultural, Sciences Division of Phytomedicine Lentzeallee 55-57, D 14195 Berlin, Germany
Interests: emaraviruses; molecular characterization of plant viruses; viruses affecting decidious trees; genetic diversity; virus-plant-vector interaction

Prof. Dr. Carmen Büttner

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Guest Editor

Humboldt-Universität zu Berlin, Faculty of Life Sciences, Albrecht Daniel Thaer-Insitute for Agricultural and Horticultural, Sciences Division of Phytomedicine Lentzeallee 55-57, D 14195 Berlin, Germany
Interests: forest virology; epidemiology; emaraviruses; diagnostics; distribution; virus transmission; ecology; virus dendrology; virome in trees

Dr. Thierry Candresse

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Guest Editor

INRAE and Université de Bordeaux, Equipe de Virologie, UMR 1332 Biologie du Fruit et Pathologie, 71 avenue E. Bourlaux, CS 20032, 33882 Villenave d'Ornon, CEDEX, France
Interests: virus; viroid; metagenomics; diagnostics; genome; virus-plant interactions; mycovirus

Dr. Risto Jalkanen
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Guest Editor

RJ Consulting, Taimelantie 25, FI 96460 Rovaniemi, Finland
Interests: general forest pathology; viruses in forest trees; boreal forests; treeline and climate; retrospective forest pathology and past climate reconstruction; rust and needle diseases; abiotic diseases

Prof. Dr. Sebastien Massart

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Guest Editor

Plant Pathology Laboratory, TERRA-Gembloux Agro-Bio Tech, University of Liège, Passage des Déportés, 2, 5030 Gembloux, Belgium
Interests: virus epidemiology; plant virome analysis; high throughput sequencing; molecular diagnostics; microbial communitites; microbiome

Dr. Tod Ramsfield

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Guest Editor

Research Scientist Forest Pathology, Canadian Forest Service, Natural Resources Canada/Government of Canada, Northern Forestry Centre, 5320 – 122 Street NW, Edmonton, AB, T6H 3S5, Canada
Interests: forest pathogen molecular diagnostics; foliar pathogens of conifers; root disease fungi; parasitic plants; ecology of soil fungi; mycorrhizal fungi

Special Issue Information

Investigations of viruses in forest ecosystems are extremely rare as compared to viruses of the agricultural and horticultural environment and they are far outnumbered by the number of studies focussed on fungal pathogens and pest insects of forest trees. Many well-characterized viruses and viroids are known from different agricultural cultivars, but only a few viruses have been commonly detected in urban and forest trees and shrubs; viroids have not been detected yet. This lack of knowledge misleads to the impression that viral diseases in forest trees are unimportant. However, viruses are probably responsible for far greater economic losses in these hosts than generally recognized because of the insidious nature of the losses since symptoms are often inconspicuous and may therefore go unnoticed.

Studies of virus diseases in tree fruit crops, grape and citrus have shown that in extreme situations causal viruses can eliminate a tree species over a very broad region. Plant viruses can alter host physiology and predisposition leading to diseased and damaged tissues or to reductions in metabolism and yield and therefore play a central role in plant health status. In contrast to other pathogens, viruses cannot be controlled by curative treatments.

A comprehensive understanding of the impact of viruses on forest tree health is therefore an important research focus, starting with their proper characterization at genome level and their association with plant stress and disease. The availability of detection protocols is also a cornerstone in the study of these viruses while a deeper understanding of their biology (host range, symptoms, transmission pathways) is required to develop appropriate prophylactic and control measures when needed to ensure a long-term economic forest stand.

We welcome articles that deal with the identification and the characterization of known and novel viruses (single or as a virome) affecting woody host species. Suitable diagnostic tools for detection of plant viruses infecting these hosts can also be reported. Emphasis is given to viruses and virus complexes that affect host species which are important in forestry or urban greens, but virus diseases and disease complexes of trees and shrub species in general will also be considered. Research reports may also focus on epidemiological issues, for instance the importance of long-lived host species as virus reservoirs, or the effects of viruses on tree health in combination with other biotic (pathobiome) and abiotic stress factors. Moreover, knowledge of viruses affecting pathogens of trees is needed. This includes plant viruses bringing benefits to their hosts. For example, knowledge of mycoviruses will provide understanding of their role in the fungal host and their potential to reduce virulence of the pathogen. Studies providing information about effects of virus infection on wood quality and yield will be of interest to the special issue as well as the report of management strategies and best practices to minimize virus diseases and prevent virus infection.

Dr. Susanne von Bargen
Prof. Dr. Carmen Büttner
Dr. Thierry Candresse
Dr. Risto Jalkanen
Prof. Dr. Sebastien Massart
Dr. Tod Ramsfield
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

plant viruses
deciduous trees
conifers
virome
pathobiome
detection
epidemiology
viral genome
viroids
mycoviruses
virus-host interaction
metabolic impact
management

Published Papers (4 papers)

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Research

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Open AccessArticle

Quantitative Distribution and Transmission of Tea Plant Necrotic Ring Blotch Virus in Camellia sinensis

and

Forests 2022, 13(8), 1306; https://doi.org/10.3390/f13081306 - 16 Aug 2022

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Abstract

Tea plant necrotic ring blotch virus (TPNRBV), which carries four positive-sense single-stranded RNA segments, causes discoloration spots and multiple necrotic ring blotches in tea trees. To understand the distribution and transmission of TPNRBV in tea trees and prevent its spread, a SYBR Green real-time quantitative polymerase chain reaction (RT-qPCR) method for detecting the four virus segments was developed. The limit of detection of RT-qPCR was 3.81, 4.73, 3.58, and 4.64 copies/μL for the four strands of TPNRBV, which was 100-fold more sensitive than conventional PCR for RNA1 detection, 10-fold for RNA2 and RNA3, and 1000-fold for RNA4 detection. Visual observation and RT-qPCR of different tea plant tissues showed that symptomatic mature leaves contained the highest TPNRBV load; the concentrations of the four RNAs in other tissues decreased or were undetectable with increasing distances from symptomatic leaves. TPNRBV did not spread efficiently through seeds, cuttings, or mechanical inoculation, but was transmitted to some tea cultivars, particularly light albinistic varieties such as ‘Zhonghuang 1’ and ‘Huangjinya’, under field conditions. Our TPNRBV detection method is useful for determining the distribution and transmission characteristics of TPNRBV and selecting tissues with the highest viral load for early diagnosis, monitoring, and management of the disease. Full article

(This article belongs to the Special Issue Viruses in Forest and Urban Trees and Shrubs)

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Open AccessArticle

Characterization of a Novel Emaravirus Affecting Ash Species (Fraxinus spp.) in Europe

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Forests 2021, 12(11), 1574; https://doi.org/10.3390/f12111574 - 16 Nov 2021

Cited by 3 | Viewed by 1369

Abstract

We identified a novel virus in diseased European ash (Fraxinus excelsior) and manna ash (F. ornus) trees exhibiting chlorotic ringspots, mottle and leaf deformation such as curling and shoestring symptoms. High-throughput sequencing (HTS, Illumina RNASeq) of total RNA isolated from diseased leaf material in combination with RT-PCR-based amplification techniques and Sanger sequencing determined five complete genome segments, each encoding a single open reading frame. Sequence analyses of RNA1–RNA5 revealed a genome organization typical for emaraviruses, i.e., (i) conserved and complementary terminal 5′ and 3′ termini of each genome segment (ii) proteins showing significant homologies to the RNA-dependent RNA polymerase (RdRP) encoded by RNA1, the glycoprotein precursor (GPP) encoded by RNA2, the viral nucleocapsid protein (N, RNA3), the movement protein (MP, RNA4), and a protein of 26 kDA (P26, RNA5) highly similar to proteins of unknown function encoded by other emaraviruses. Furthermore, we identified spherical particles (double-membrane bodies, DMB) of different sizes (70–80 nm in diameter) which are typical for emaraviruses exclusively in virus-infected leaf tissue exhibiting mottle and leaf deformation. Sequence comparison and phylogenetic analyses confirmed the identified novel virus as a new member of the genus Emaravirus. We established a species-specific RT-PCR detection protocol and could associate the observed disease symptoms with the infection of the novel emaravirus in F. excelsior and F. ornus. Therefore, we propose the name ash shoestring-associated emaravirus (ASaV). Investigation of ASaV-infected sample trees originating from different locations in Switzerland, Germany, Italy and Sweden provided a wide geographical distribution of the virus in affected ash species. To our knowledge, this is the first confirmation of an emaravirus affecting ash tree species with shoestring symptoms of leaves in Europe. Full article

(This article belongs to the Special Issue Viruses in Forest and Urban Trees and Shrubs)

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Open AccessArticle

Identification of an Emaravirus in a Common Oak (Quercus robur L.) Conservation Seed Orchard in Germany: Implications for Oak Health

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Forests 2020, 11(11), 1174; https://doi.org/10.3390/f11111174 - 04 Nov 2020

Cited by 7 | Viewed by 1889

Abstract

We observed the health status of oak trees in a conservation seed orchard for over twenty years, focusing on characteristic virus-suspected symptoms. The orchard was established in 1992 in Kreuztal, North Rhine-Westphalia (Germany) with 1302 seedlings in 186 clusters. The number of seedlings showing chlorotic ringspots and mottle on leaves has fluctuated annually, but has increased from 3.3% to 12.1% in the last 20 years; the number of affected clusters has risen from 8% to 25.9%. A scientific breakthrough was the identification of a novel virus related to members of the genus Emaravirus in diseased oak by high-throughput sequencing (HTS). Screening of the oak seedlings in three consecutive years, using a newly established virus-specific diagnostic reverse transcription polymerase chain reaction (RT-PCR), confirmed the virus infection and revealed a close to 100% association between the observed leaf symptoms and the novel virus. As no other plant virus could be identified in the HTS-datasets, we assume the novel virus is primarily causing the symptoms. To reliably detect the novel virus in oaks, RT-PCR targeting the viral RNA3 or RNA4 should be applied in routine testing of symptomatic leaf tissue. It was obvious that most groups with virus-infected plants cluster, with only five out of the 42 affected groups being offside, not bordering on other affected groups of plants. There was no clear correlation between the detection of the virus and the overall vitality of the seedlings. There was no relation between seedling performance and presence or absence of viral infection. Forecasts on the future growth behavior of these virus-infected oak trees are therefore not possible. Full article

(This article belongs to the Special Issue Viruses in Forest and Urban Trees and Shrubs)

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Review

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Open AccessFeature PaperReview

The Complex World of Emaraviruses—Challenges, Insights, and Prospects

Shaheen Nourinejhad Zarghani

Thierry Candresse

Carmen Büttner

and

Susanne von Bargen

Forests 2022, 13(11), 1868; https://doi.org/10.3390/f13111868 - 08 Nov 2022

Viewed by 1205

Abstract

Emaravirus (Order Bunyavirales; Family Fimoviridae) is a genus comprising over 20 emerging plant viruses with a worldwide distribution and economic impact. Emaraviruses infect a variety of host plants and have especially become prevalent in important long-living woody plants. These viruses are enveloped, with a segmented, single-stranded, negative-sense RNA genome and are transmitted by eriophyid mites or mechanical transmission. Emaraviruses have four core genome segments encoding an RNA-dependent RNA polymerase, a glycoprotein precursor, a nucleocapsid protein, and a movement protein. They also have additional genome segments, whose number varies widely. We report here that the proteins encoded by these segments form three main homology groups: a homolog of the sadwavirus Glu2 Pro glutamic protease; a protein involved in pathogenicity, which we named “ABC”; and a protein of unknown function, which we named “P55”. The distribution of these proteins parallels the emaravirus phylogeny and suggests, with other analyses, that emaraviruses should be split into at least two genera. Reliable diagnosis systems are urgently needed to detect emaraviruses, assess their economic and ecological importance, and take appropriate measures to prevent their spread (such as routine testing, hygiene measures, and control of mite vectors). Additional research needs include understanding the function of emaravirus proteins, breeding resistant plants, and clarifying transmission modes. Full article

(This article belongs to the Special Issue Viruses in Forest and Urban Trees and Shrubs)

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