Brief Summary of Minutes of Annual Meeting

Ioannis Tzanetakis, University of Arkansas, was elected as Secretary of the annual WERA-20 2019 meeting.  Additionally, it was unanimously agreed that WERA-20 2020 will be hosted by the University of Hawaii.  Subsequently, John Hu, University of Hawaii, is proposing the meeting to be held on May 22-26, 2020.  Below are the minutes of the meeting taken by the Secretary: 

Naidu Rayapati, Washington State University

Surveys were conducted to identify economically important viruses of grapevine and blueberry in Washington State, and determine their distribution.  In grape, leafroll-associated viruses, particularly grapevine leafroll-associated virus 3 (GLRaV-3) (87% of the same tested positive for this virus), red blotch, fanleaf, vitiviruses, and nepoviruses are present.  The ratio of GLRaV-3 and grapevine red blotch virus (GRBV) is 11:1 in WA vineyards.  Symptoms of leafroll and red blotch cannot be distinguished visually.  Tobacco ringspot virus (TRSV) starts to emerge as a problem.  Nursery material has less than 1% of GLRaV-3 and no GRBV.  In blueberry, decline was observed on Draper in association with TRSV.  This is the first report of TRSV in blueberry WA and the pacific Northwest.  Blueberry mosaic-associated virus and Blueberry latent virus were also detected. 

Scott Harper, Washington State University

Surveys of graft-transmissible pathogens in stone fruit trees showed a high incidence of western-X phytoplasma (24%), little cherry virus 2 (14%) and a lower incidence of little cherry virus 1 (less than 1%).  Interestingly, little cherry disease is primarily distributed in the north and western X disease in the south of Washington State.  Western X is present in peaches and nectarines, pollinator trees and weeds.  In apple, declining trees are reported.  The phloem tissue of declining trees is dying, and several known but also new viruses are identified in declining trees.  In hops, viruses and viroids are detected using in-situ hybridization. 

Lauri Guerra, Washington State Department of Agriculture

Registration and certification in Washington State is based on the process rather than the plants.  Testing of trees showed that the majority of positive samples are infected by ilarviruses, several positives are infected with cherry leafroll virus (CLRV) but none of the samples has ever tested positive for plum pox virus (PPV).  For nepoviruses, there is a need to monitor weeds or use sentinel plants.  In stoolbeds, efforts are underway to clean the material from apple chlorotic leaf spot virus (ACLSV) and apple stem grooving virus (ASGV).  Challenges are nepoviruses, little cherry disease, western X disease, cherry virus A and new viruses. 

Cindy Cooper, Washington State Department of Agriculture

Efforts to revise the grape certification in Washington State are almost complete.  Some insect vectors, viruses and pests have been added to the quarantine list. 

Kari Peter, Penn State University

Apple decline is a major issue.  Several known viruses have been identified in affected trees but none of them is associated with decline.  Apple luteovirus 1 (ALV1) was identified by high throughput sequencing in declining trees.  Some nurseries have 100% of their stoolbeds infected with ALV1.  Rapid apple decline is on the uptick in Pennsylvania because of the multiple rain events. 

Katya Nikolaeva, Pennsylvania Department of Agriculture

Surveys of grapes, stone fruits and pome fruits for phytoplasmas identified new species or subspecies.  The infection rate was low: 1% for grapes and apples, and 5% for peaches.  Phytoplasma americanum was identified in strawberry. 

Ruhui Li, USDA-ARS

Two novel viruses were identified in cherry by high throughput sequencing: cherry robigovirus 5 and cherry trichovirus 3.  Neither of them is very common. 

John Hu, University of Hawaii

Banana bract mosaic virus was identified in ginger showing mosaic symptoms.  The virus is similar to the ones found in India and the Philippines.  This virus is transmissible from ginger to banana by the banana aphid.  Canna yellow mottle virus (CaYMoV) and banana streak virus were also found in plants.  Stunted plants had CaYMoV and bean common mosaic virus. 

Shulu Zhang, Agdia, Inc

AmplifyRP Acceler8 and AmplifyRP Acceler8 XRT assays based on the end-point rapid DNA amplification technology were developed and released for 13 pathogens and discovery purpose (universal kits). 

Larissa Osterbaan, Cornell AgriTech

Grapevine fanleaf virus (GFLV) mutants derived from strains F13 (asymptomatic) and GHu (vein clearing) were produced to identify the molecular determinant of symptom development in Nicotiana benthamiana.  Symptom determinants mapped to the 21 nt/7 aa at the C-terminus of the RNA1-coded 1E^Pol.  Symptoms are protein associated, rather than nucleotide-based, and residue 802 determines vein clearing symptomology. 

Joseph Postman, USDA-ARS

Among the pathogen affecting the National Clonal Germplasm Repository in Corvallis, ORm Actinidia yellow leaf spot is recognized as a new disease of unknown etiology.  Tomato ringspot virus (ToRSV) is spreading in Ribes.  BRV is present in the collection but in only four plants.  Blueberry shock virus (BlShV) has spread in the Vaccinium collection.  There are accessions with potential resistance to BlShV.  In apple, knobbed Russet is suspected of being of viral origin.  For Xyllela, Oregon and Washington are free zones.

 Bob Martin, USDA-ARS

Surveys of Rubus for viruses.  At the G1 level, it is important to start clean from all viruses.  Nurseries should stay clean using best management practices and testing for ‘canary’ viruses.  In production fields, virus identity is not important as long as no disease is identified.  A new luteovirus and two new cytorhabdoviruses were identified in raspberry in northern US.  Eradication efforts of blueberry fruit drop-associated virus are in progress in Washington State. 

Yannis Tzanetakis, University of Arkansas

A new detection protocol for the detection of viruses and taxonomic placement of eriophyiod mites using a single individual was developed and optimized.  Using this assay, only viruses in vector species are detected, making this protocol a valuable tool to identify potential eriophyiod vectors of known and new diseases. 

Maher Al Rwahnih, UC-Davis

Introduced grape material can receive a provisional release following high throughput sequencing.  Are indicators that are used for biological assays of known viruses still useful since known viruses are identified based on laboratory techniques?  Efforts within RSMP 35 call for the elimination of agents for which no type isolate or sequence is available. 

Margaret Kelly, New York State Department of Agriculture and Markets

Best management practices are important but nurseries need to sell plants.  Plants other than those available in foundation blocks can be considered for certification if there is not enough foundation material, they are obtained from reliable sources, and undergo extra testing. 

Christie Almeyda, North Carolina State University

The pipeline for the production of clean plants for breeders at MPRU based on testing-clean up (heat therapy)-storage-release was outlined.  Meristems from tissue culture plants collected at 39°C show approximately 50% survival.  MPRU serves breeding programs in the Southeast and companies in Florida and the West Coast.  Berries and grapes were tested for several viruses. 

Anna-mary Schmidt, Canadian Food Inspection Agency

CFIA is ISO 17025 certified.  Standard operating procedures and method development were advanced to support the implementation on high throughput sequencing in diagnostics.  The technology is evaluated for sensitivity, reproducibility and repeatability 

Oscar Hurtado, USDA-APHIS

Latent pome viruses are the most commonly intercepted agents at the Plant Germplasm Quarantine Program (PGQP).  More than 360 plants, including over 120 pome fruits, have been gone through high throughput sequencing at PGQP.

A virus like citrus concave gum-associated virus was detected in pear from 22 countries.  Testing efforts of the Malus germplasm repository in Geneva, NY are under way. 

Yazmin, Rivera, USDA-APHIS

The performance of the MinIon technology was tested using ribo-depleted and smallRNA.  The MinIon cDNA kit gives better results than RNA.  A higher mapping to an RNA virus is obtained using the RNA kit but a lower percentage of complete genomes compared with RNA. 

Libby Cieniewicz, Cornell Agritech

Epidemiological studies of grapevine red blotch virus (GRBV) showed an annual increase of virus incidence by 10% in proximity to riparian areas where aggregation of diseased vines occur.  Populations of the three-cornered alfalfa hopper (TCAH) pick in summer months in Napa Valley, California.  More TCAH are found in grapes close to the riparian zone.  No spread of GRBV was found in NY.  Wild vitis virus 1 (WWV-1), a new grablovirus, is only present in wild Vitis species in California.  GRBV was found 20% of wild vines in California and WVV-1 in only 7 of them.  Legume cover crops have not tested positive for GRBV. 

Keith Perry, Cornell University

Grapevine DNA viruses consist of two badnaviruses and four grabloviruses.  Rolling circle amplification and loop-mediated isothermal amplification are very sensitive and do not require the need of nucleic acid extraction from plant tissue.  RNAseq revealed novel transcription patterns of some GRBV genes.  GRBV is distributed in many areas around the globe although it appears to be of North American origin.

Naidu Rayapati, Washington State University

In a recent industry-wide survey, vineyard health was identified as one of the top research priorities for sustainable growth of the grape and wine industry in Washington State. Among diseases caused by different pathogens, virus diseases are by far the major constraints affecting vineyard health and longevity.  With increased expansion of wine grape (Vitis vinifera) acreage in the state, implementing an integrated approach of planting virus-tested ‘clean’ planting materials and post-planting management of virus diseases has been recognized as an effective strategy for maintaining healthy vineyards.  Towards this objective, diagnostic activities were conducted to improve the sanitary status of grapevines in registered mother blocks maintained by certified nurseries.  A composite sampling strategy in combination with molecular diagnostic assays were used for high-throughput and reliable testing of grapevine samples from certified nurseries.  The results obtained so far showed the absence of grapevine red blotch virus (GRBV) and very low incidence of grapevine leafroll-associated virus 3 (GLRaV-3) in registered mother blocks.  Testing grapevine samples received from growers indicated that GLRaV-3 is more common than other GLRaVs and GRBV, independent of cultivars and geographic origin of samples.  Although a few additional viruses were documented in commercial vineyards, they were detected largely as co-infections with GLRaV-3 and/or GRBV and found causing asymptomatic infections when present alone.  Participatory approaches were pursued in collaboration with growers and nursery personnel to translate science-based knowledge for strengthening grapevine supply chain and to deploy integrated measures for controlling virus diseases in vineyards.  For blueberries, Washington State became in recent years the national leader in blueberry production and the crop acreage is increasing rapidly in eastern Washington.  Virus-like symptoms were observed in two blueberry fields affecting crop production.  Leaf samples showing symptoms were tested by serological and molecular diagnostic assays and analyzed next-generation sequencing to identify viruses present in affected plants.  In one field, blueberry mosaic-associated virus and blueberry latent virus were detected in symptomatic plants.  In another field, tobacco ringspot virus was detected in symptomatic plants.  Together with a previous report of the occurrence of TRSV in wine grapes, the finding of TRSV infecting blueberries highlights the potential significance of TRSV as an emerging virus problem to several specialty fruit crops in eastern Washington.  Knowledge of viruses and improved understanding of their complex biology helped growers to deploy robust tactics for management of virus diseases in vineyards. 

Scott Harper, Washington State University

Over the past year, research was focused on understanding and developing diagnostic methods and control measures for two major diseases affecting tree fruits in the Pacific Northwest: Little cherry disease and apple decline. We have been active in extension and outreach for affected growers, particularly for little cherry disease which has reached epidemic proportions in Washington State. In the past season, we have tested a total of 1945 cherry samples for the two pathogens that cause this disease, allowing growers to make informed management decisions about whether to remove trees in orchards. We are also actively researching the pathways by which the two unrelated pathogens, little cherry virus-2 and Candidatus Phytoplasma pruni, cause what is basically the same disease, small, bitter or acrid cherries, with the hope of identifying pathogenesis related genes of effectors, so that resistant or tolerant cherry varieties can be bred for commercial production.  Work on apple decline has increased engagement with the apple industry, identifying a number of pathogens that may be involved with this disease, and require further study.  This work has increased grower awareness of virus-like pathogens and the need for active management.  Finally, we have been actively developing and publishing new and improved diagnostic methods for general use in detecting pathogens in both pome and stone fruit and for virus control. 

Ekatarina Nikolaeva, Pennsylvania Department of Agriculture

The Pennsylvania Department of Agriculture (PDA) in cooperation with Penn State University conducted 2018 Farm Bill-funded surveys for exotic diseases in orchards and small fruits.  Orchard survey targets included plum pox virus, Asian pear blight (Erwinia pyrifoliae), Asiatic brown rot (Monilia polystroma), Apple brown rot (Monilinia fructigena), Apple proliferation (Candidatus Phytoplasma mali), European stone fruit yellow (Ca. Phytoplasma prunorums), and Almond witches’ broom (Ca. Phytoplasma phoenicium).  Small fruit survey targeted Asian pear blight (Erwinia pyrifolia), tomato black ring virus, Australian grapevine yellows (Ca. Phytoplasma australiense), Flavescence dorée phytoplasma (Ca. Phytoplasma vitis), and Bois noir phytoplasma (Ca. Phytoplasma solani).  No exotic targets were detected, but we did confirm the presence of Ca. Phytoplasma pruni (16SrIII-A group, X-disease group) in peach and grapes, and Ca. Phytoplasma pyri (16SrX, Apple Proliferation group) in pears.  In 2018, Ca. phytoplasma americanum has been detected in a strawberry plant (Fragaria × ananassa) with symptoms of stunting and unseasonal reddening and distortion of leaves.  To our knowledge, this is a first report to indicate that Fragaria × ananassa can serve as a host of ‘Ca. Phytoplasma americanum’.  In addition, data gathering was continued on rapid apple decline. Since August 2018, PDA inspected 27 apple blocks from 14 farms located in seven Pennsylvania counties for symptoms and signs of rapid apple decline, including the presence of declining trees, unseasonal tree discoloration and defoliation, brown cankers around graft union, and presence of root suckers.  The main target was the newly described apple luteovirus 1 (ALV-1) which may play a role in RAD.  A total of 121 samples from scion leaves, bark, blossoms, fruits, and root sucker leaves were found positive for ALV-1 using one-step reverse transcription (RT)-PCR assay developed by USDA ARS National Germplasm Resources Lab.  The virus was detected from a wide range of apple varieties including Crimson Crisp, Fuji, Gala, Honeycrisp, Red Delicious and Golden Delicious.  Most of the ALV1 positive trees (67%) were grafted on M9 rootstocks while only few positive trees found on Bud 9, Emla 26, M26, M7A, and G935.  Our results suggest the virus does not distribute equally within the tree and the number of positive tree scaffolds increases during the infection process.  ALV-1 was detected on some trees in combination with 1-3 apple latent viruses (ApMV, ASGV, ASPV, ACLSV) but there was no consistency in virus combinations.  The work on determination of ALV1 pathogenicity was started in August 2018.  Two hundred and twelve M9 rootstocks (not grafted) trees from different suppliers were evaluated for the presence of ALV1. Surprisingly, about 50% of the tested trees were found positive.  ALV1 positive trees with a single virus infection were used for grafting with ALV1 negative budwood.  We plan to revisit grafted trees this summer to evaluate virus transmission to the scion of the grafted trees and possible symptom development.  Finally, PDA continues to operate the Fruit Tree Improvement Program (FTIP), a specialized virus-tested fruit tree certification program. Three nurseries have been participating in the FTIP last year. Over 2,000 samples were tested for viruses of concern, including Prunus necrotic ringspot, prune dwarf virus, tomato ringspot virus, and plum pox virus. No PPV was detected in rootstock blocks or in registered source blocks. PNRSV (1.5%) remains the most commonly found virus in Prunus in PA nurseries. PDV (0.6%) and ToRSV (0.2%) finds in registered blocks and nursery production blocks are very rare. All blocks met virus-testing requirements for FTIP certification.

Ruhui Li, USDA-ARS

Research involved characterization and detection of plant viruses infecting tree fruits and small fruits.  The characterization of novel viruses or variants infecting these crops provides a foundation for detection and elimination of these viruses from germplasm and seedlings.  Two new viruses have been discovered from currants, and preliminary surveys showed that these viruses were common, and they may be associated with viral diseases. 

John Hu, University of Hawaii

Bean common mosaic virus (BCMV) is a species of the genus Potyvirus in the family Potyviridae.  BCMV is transmitted mechanically and in a non-persistent manner by several species of aphids.  Flowering ginger (Alpinia purpurata) is an important ornamental crop in Hawaiʻi that has been previously shown to harbor single and mixed infections by the potyvirus banana bract mosaic virus (BBrMV) and the badnavirus canna yellow mottle virus (CaYMV).  In March 2019, flowering ginger plants with virus-like symptoms that were distinct from the mosaic and streaking symptoms produced by dual infections of BBrMV and CaYMV were observed on Oʻahu, Hawaiʻi.  The symptoms included green mosaic patterns along leaf veins, plant stuntedness, and chlorosis. Symptomatic leaf samples were collected and total nucleic acids were extracted for testing by PCR.  Using degenerate primers, the samples were assayed for the presence of potyviral and badnaviral infection.  All symptomatic samples were found to be infected by CaYMV, but BBrMV was not detected.  Direct Sanger sequencing and analysis of the resultant PCR products generated using the potyviral primers indicated the presence of BCMV.  BLASTN search showed that the potyviral sequence (MN073501) shared 93.8% identity to BCMV strain A1 (MK282414), a new strain of BCMV characterized from Lima Bean in Hawaiʻi.  To confirm BCMV infection, a BCMV-specific primer set (BCMV-CIg-F 5′-AGCTCGCCACATAAACAAGC-3′ and BCMV-CIg-R 5′-CTCAGAATGCGCGGRTTGAGC-3′) was designed to target the cylindrical inclusion (CI) protein gene.  The expected 350-bp PCR products were obtained and the resulting sequences (MN043985) displayed a high similarity with the corresponding CI protein gene from a BCMV isolate obtained from a Sesamum indicum plant growing in China (MK282414), sharing 96.56% and 95.28% identity at the nucleotide and amino acids levels, respectively.  Subsequently, the samples also tested positive using a potyvirus group-specific ELISA and a BCMV-specific ELISA following the manufacturer’s directions (Agdia, Elkhart, IN). In May 2019, four additional samples were collected from the same location.  The BCMV primer-specific set was used in RT-PCR to verify infection by BCMV based on the amplification of PCR fragments of the expected size.  The results of these assays further confirmed the presence of BCMV in flowering ginger.  To our knowledge, this is the first report of BCMV naturally infecting flowering ginger.  It is unclear if its presence in ginger is contributing to the current serious die-back disease of flowering ginger in Hawaiʻi. Additional research is needed to determine the potential cause of the threat to the ginger industry in Hawaiʻi.  Collaborative work on BCMV is with Dr. Karasev, and on ginger and papaya viruses with Dr. Al Rwahnih.

Shulu Zhang, Agdia, Inc

Early detection and effective control of plant pathogens is very important to prevent their wide spread resulting in serious economic losses in crops like cherries, citruses, grapes, hops, peaches or plums.  Agdia's AmplifyRP^® utilizes a leading isothermal amplification technology called recombinase polymerase amplification (RPA) and has recently become a versatile diagnostic tool for rapid and accurate detection of nucleic acids in all types of plant pathogens.  So far, Agdia has commercialized 13 AmplifyRP^® kits specific to single species/strains of diverse pathogens and 2 AmplifyRP^® Discovery kits suitable for any pathogens.  Among the pathogen-specific kits, there are 7 kits in AmplifyRP^® Acceler8^® format, 3 kits in AmplifyRP^® XRT format and 3 kits in AmplifyRP^®  XRT⁺ format.  Two of these kits, AmplifyRP^® XRT for Clavibacter michiganensis subsp. nebraskensis and AmplifyRP^® XRT⁺ for Dickeya spp. were released since 2018 WERA-20 meeting.  There are additional 14 pathogen-specific AmplifyRP^® kits in development. Agdia has acquired the intellectual properties right for AmpliFire and started to produce and offer this portable, battery-operable fluorescence reader.  

Bob Martin, USDA-ARS

The project on blueberry fruit drop-associated virus is leading to the eradication of this virus from commercial blueberries in the U.S.  In a national survey carried out in 2015-2018, this virus was only detected in northwest Washington.  For the past three years we have been working with growers in northwest WA to eradicate this virus from their fields.  Approximately 2500 samples were tested representing all the major blueberry production areas in the U.S.  After the first year of this project we have identified an enamovirus that is only present in the northeast U.S. and eastern Canada thus far.  This virus is being studied to determine if it can cause raspberry leaf curl disease in Rubus cultivars that were grown in that region in the 1940s-1970 when the disease was common.  We have also identified two novel rhabdoviruses but they are very limited in distribution at this time (one plant each), though one is a strain of raspberry vein chlorosis virus, which is considered a European virus.    We are working with entomologists to identify vector(s) of GRBV in Oregon, where the three-cornered alfalfa hopper is very rare but we are seeing significant spread of the virus in commercial vineyards.  We are also working with viticulturists and enologists at OSU to evaluate the impact of viticultural practices on fruit quality from plants infected with GRBV. 

Yannis Tzanetakis, University of Arkansas

In collaboration with colleagues, several of which participate in WERA-20, we are working on the characterization and population structure of several viruses in strawberry (rhabdovirus), blueberry (luteo and carlavirus) and blackberry (allexi-, ifla- and reovirus).  This information is used in the development of detection protocols that have the ability to detect the vast majority of isolates that circulate in the United States.  One of the highlights of the year is the development of a new detection protocol that allows for the detection of viruses and taxonomic placement of eriophyiod mites using a single individual.  In our experiments we were only able to detect viruses in vector species, making this protocol a valuable tool when it comes to identifying potential eriophyiod vectors of known and new diseases.  To harmonize certification guidelines among states and commodities, we have obtained new funding for two meetings between representatives of several specialty crops, federal and state regulators.

Maher Al Rwahnih, University of California

At Foundation Plant Services (FPS), we continue to make advances in developing and refining our methods using high throughput sequencing (HTS) as a superior diagnostic tool.  We have used sequence information generated by HTS analysis to design new, specific PCR primers for use in PCR diagnostics. In addition, HTS proves to be an invaluable tool in the discovery of unknown viruses and in establishing a baseline analysis of the virome of a crop.  Below are some specific accomplishments:

• We have greatly improved the efficiency of diagnostic laboratory assays for grapevine leafroll-associated virus 3 (GLRaV-3). GLRaV-3 has an exceptional number of highly diverse variants.  Recent studies based on genome-wide phylogenetic analysis demonstrated that GLRaV-3 variants can be divided into eight distinct groups, six of which have been identified in California.  This level of genetic diversity makes it very difficult to identify a conserved region common to all isolates for design of a single qPCR-based assay, however using six different variant specific assays is not desirable.  FPS analyzed GLRaV-3 sequence data available in GenBank and those generated in-house to develop a new RT-qPCR assay with the capacity to detect all known GLRaV-3 variants.  The new assay, referred to as FPST, was challenged against samples that included plants infected with different GLRaV-3 variants and originating from 46 countries.  The FPST assay detected all known GLRaV-3 variants, including the highly divergent variants, by amplifying a small highly conserved region in the 3’ untranslated terminal region (UTR) of the virus genome.  The reliability of the new RT-qPCR assay was confirmed by a newly developed enzyme linked immunosorbent assay (ELISA) that can detect all known GLRaV-3 variants characterized to date.  The assay was further validated with 2415 samples obtained from the USDA National Clonal Germplasm Repository in Winters, CA, the Davis Virus Collection at UC-Davis, the FPS pipeline of foreign and domestic introductions, selected vineyards in the main grape-growing areas of California, and samples provided by international collaborators.  This new assay is being shared with stakeholders, thus benefiting growers, researchers, and diagnostic labs involved in the grapevine industry in the US and around the world.
• Last year, we reported the discovery of a novel vitivirus, named grapevine virus J (GVJ). Vitiviruses are ssRNA(+) viruses in the family Betaflexiviridae (subfamily Trivirinae).  This year we report two novel vitiviruses: grapevine virus L (GVL) and grapevine virus M (GVM).  GVL has a genomic sequence that is 7,607 nt long, including a typical genome organization of open reading frames (ORFs) encoding a replicase (RP), a 22 kDa protein, a movement protein, a coat protein (CP) and a nucleic acid binding protein.  GVM was discovered by high-throughput sequencing in samples of the American hybrid bunch grape cultivar Blanc du Bois in Texas.  The genome length is 7,387 nt, excluding the polyA tail. The genome sequence contains five ORFs that are homologous and phylogenetically related to ORFs of grapevine-infecting vitiviruses.  In the last few years at least 5-10 new vitiviruses have been discovered.  This high number of discoveries led us to launch a survey in 2018 to determine the incidence of the novel vitiviruses (GVG, GVH, GVI, GVJ and GVL) in California.  The survey included 2,327 samples from commercial vineyards (728), FPS’ introduction pipeline (390), and the USDA National Clonal Germplasm Repository (1,209).  Results of the survey showed that all the novel vitiviruses were identified in California, 55 of the 2,327 samples were positive, and mixed infections were common.
• Rose rosette disease (RRD), caused by rose rosette virus (RRV), is a highly destructive disease of roses in the eastern U.S. In 2017, two symptomatic plants from a commercial nursery in Wasco, CA and three garden roses in Bakersfield, CA were positive for RRV.  To our knowledge, this was the first report of rose rosette virus associated with rose rosette disease affecting roses in California.  Given the high wholesale value of the rose industry at US$ 17.6 million in 2016, a widespread RRV outbreak would be devastating.  This year rose plants in Dixon and Sacramento, California with disease symptoms similar to RRD were examined and tested for RRV at FPS.  Samples were also sent to the USDA-ARS lab in Beltsville, Maryland to inspect for the vector but no vector was found.  FPS is taking all necessary measures to reduce the risk of introducing RRV to the FPS foundation rose collection, the largest public collection of virus-tested roses in the United States and is not accepting introduction of material from sources in which RRD is known to occur.
• Little cherry disease (LCD), associated with little cherry virus-1 (LChV-1) or -2 (LChV-2), is a common problem of cherries which occurs worldwide, causes unmarketable fruit and often results in tree or orchard removal. Most of the new cherry rootstocks used in cherry production are interspecific Prunus hybrids which introduces an increased risk of an adverse reaction (hypersensitivity) to some viruses.  Hypersensitive reactions exhibit graft union gum exudation, premature abscission, and tree death within one or two growing seasons and have been shown to occur in Prunus when infected with prunus necrotic ringspot virus (PNRSV) and prune dwarf virus (PDV).  FPS has begun evaluating the effects of LChV-1 and LChV-2 on 16 different popular Prunus rootstocks.  All rootstocks will be grafted with a scion variety from the same accession.  Observations of bud take and tree performance will be recorded and evaluated for two years. We are currently in the second year of this project; the first trial has been planted in the field.  Rootstocks will be rated for sensitivity to LChV-1 and LChV-2 and this information will be shared with growers and nurseries to assist in making rootstock selection decisions.
• As the fruit tree program at FPS is experiencing significant growth, FPS is working to improve fruit tree virus detection. FPS is running HTS versus the standard biological assay in side-by-side studies to accumulate comparative data.  This work will help support our request to revise the Prunus 588 Controlled Import Permit SOP.  Currently, the permit requires introduced plants to be held inside greenhouses and screenhouses.  FPS would like to have the ability to plant HTS negative plants in the field.  In addition, we would like to remove the unnecessary poorly performing woody indicators, Canindex and Kwanzan.  We are also harmonizing our efforts with the Plant Inspection Station in Beltsville, Maryland and the Clean Plant Center Northwest, in Prosser, Washington, pursuing similar protocol revisions and establishing a framework for the evaluation of risks posed by new virus discovered by HTS.
• The development and validation of real time quantitative PCR assays for the detection of fruit tree viruses is a new project. The objectives of the project are to evaluate current published assays and develop new assays, if needed. Representative sets of genome sequences of the targeted viruses were compiled, and current published primers were evaluated.  New genetic data were incorporated and used to construct new and improved RT-qPCR assays that have been validated to efficiently and specifically detect 13 different pathogens.  Next steps in the project are to design RT-qPCR assays for pear decline and apple stem grooving virus, complete validation of all assays, and large-scale validations of assays with screening samples from commercial orchards.
• The value of using virus-tested material was documented in two recent papers. Research presented in Economic Benefits from Virus Screening: A Case Study of Grapevine Leafroll in the North Coast of California presents the costs and benefits of a virus screening program for Grapevine Leafroll associated Virus-3 (GLRaV-3) in the North Coast region of California.  Grower costs and benefits from using GLRaV-3-free vines were computed and extrapolated to the North Coast wine grape industry as a whole.  Economic benefits from the GLRaV-3 testing, therapy and distribution programs were found to be in excess of $20 million per year for the region, and substantially outweighed the costs.  The results showed potential benefits from removing and replacing diseased vines rather than leaving them in the vineyard where they can be foci for disease spread.  In addition, significant costs were associated with disease entering from infected vines in neighboring properties.  In a second paper, research presented in Virus surveys of commercial vineyards show value of planting certified vines demonstrates the value of selecting certified vines for new plantings.  Viruses cost the California wine grape industry as much as $91,661 per acre over the life of a vineyard.  In the North Coast wine-growing region, mixed infections were predominant in older vineyards, while recently planted certified vines did not have mixed infections.  Planting certified material regulated by the California Grapevine Registration and Certification program is a first step toward managing viruses.
• While HTS remains a powerful new technology with significant benefits, there are technical challenges associated with the technology that warrants the establishment of guidelines for its use in plant certification and quarantine programs. We have begun efforts in a collaborative project to coordinate the development of minimum basic requirements for the adoption of HTS technologies, including nucleic acid extractions, library preparation, depth of sequencing and bioinformatics, for the detection of viral pathogens.

Anna-mary Schmidt, Canadian Food Inspection Agency

The Centre for Plant Health continues to test a sampling of accessions taken from grapevine and tree fruit shipments from Canadian approved foreign certification programs in the United States, France and Germany for grapevines, and the United States, France, Belgium, Germany, Netherlands and United Kingdom for tree fruit.  Non-certified material is also accepted and tested, and must be routed directly to the Centre for Plant Health PEQ facility for a full range of testing before release.  This material includes imports from non-approved foreign sources or domestic breeding programs.  Additionally, the Centre for Plant Health does a limited amount of regulatory testing for virus and virus-like diseases of berry crops.  The testing requirements for imports are determined on a case-by-case basis depending on the origin of the material.  Since Canada does not have a national small fruit certification program for exports, all testing for export is also done on a case-by-case basis depending on the requirements of the importing country. Furthermore, the tissue culture facility at the CFIA Sidney Laboratory supplies virus-tested rootstock and indicator plants for field and greenhouse woody bioassay testing.  Upon request, the facility may produce small numbers of Generation 1 tissue culture initiates, from the CFIA’s tree fruit and grapevine virus-tested repository, for domestic or international distribution.  This facility also receives and maintains tissue culture plants from international sources for inclusion in the CFIA Sidney Laboratory’s virus testing program. The tissue culture facility plays an integral part in the virus elimination service of the Sidney Laboratory. Virus elimination, when requested, is conducted on grapevine varieties using meristem culture following in vivo heat therapy of infected plants, and virus elimination of small fruit and tree fruit varieties occurs with meristem or microshoot culture following in vivo heat therapy.  Finally, the Sidney Laboratory staff is involved in various plant-health related groups and committees including:

• NAPPO working group: Review of RSPM 35 "Guidelines for the Movement of Stone and Pome Fruit Trees and Grapevines into a NAPPO Member Country";
• NAPPO panel for the development of Next Generation Sequencing (NGS) standards for plant virus diagnostics;
• Canadian Grapevine Certification Network (CGCN);
• BC Plant Protection Advisory council for grapevines;
• International Council for the Study of Viruses and Virus-like Diseases of Grapevine;
• Food and Agricultural Organization (FAO) International Plant Protection Convention (IPPC) Technical Panel on Diagnostic Protocols (TPDP);
• Plant Health Quadrilateral (Canada, USA, New Zealand and Australia) Working Groups: “DNA barcoding”; “Diagnostic Collaboration” and “Managing regulatory issues arising from new diagnostic technologies”;
• Genomics Research and Development Initiative;
• Collaborative projects as part of the Euphresco (European Phytosanitary Research Coordination) Network (a network of European organisations funding research projects and coordinating national research in the phytosanitary area);
• International Organization for Standardization working group for “Horizontal methods for molecular biomarker analysis”

Oscar Hurtado, USDA-APHIS, Plant Germplasm Quarantine Program

The training received at Foundation Plant Services as well as the use of pipelines and UC Davis cluster HP computing facilities for high throughput sequencing (HTS) data analysis has enabled the Plant Germplasm Quarantine Program to move towards the implementation of HTS as a routine diagnostic tool in the fruit tree program. 

Keith Perry and Marc Fuchs, Cornell University

We documented the role of grapevine red blotch virus (GRBV) in red blotch disease by fulfilling Koch’s postulates using infectious clones of a representative isolate of each of the two phylogenetic clades of virus.  Agro-inoculated Vitis vinifera vines that became infected with GRBV manifested typical red blotch disease symptoms.  We also developed a quantitative PCR for the detection of GRBV and identified the optimal time of the year and best tissue for optimal diagnosis.  Additionally, we developed a rapid diagnostic assay for GRBV based on loop-mediated isothermal amplification (LAMP).  This assay should have of high interest for onsite diagnosis.  In parallel, a novel grablovirus, wild Vitis virus 1 (WVV1), was identified from non-cultivated Vitis sp. in California.  No information is available on the potential role of WVV1 in disease etiology.  Furthermore, progress was made on the ecology of grapevine red blotch virus by documenting a 10% annual increase in virus incidence in a vineyard edge proximal to a riparian area in California where disease vines are aggregated.  In the remaining of the vineyard, annual disease progress was lower (2-3%).  Also, a statistically strong association was found between the distribution of GRBV-infected vines and viruliferous three cornered alfalfa hoppers (TCAH) in a diseased vineyard, suggesting that TCAH is a vector of epidemiological significance.  Moreover, a lower TCAH population was found associated with a reduced annual increase of GRBV incidence in California.  This suggested that the TCAH population density could play a role in disease dynamics.  To the contrary, no spread of GRBV was documented in a diseased vineyard in New York.  Finally, GRBV was found widespread in wild grapevines in California, but not in New York.  Overall findings on disease ecology informed disease management tactics that were disseminated to growers, vineyard managers, extension educators and service providers.

Al Rwahnih, M., Golino, D. 2018. Prospects and challenges of high throughput sequencing for viral pathogen diagnosis and expedited release of quarantined propagative plant material. American Phytopathological Society. Boston, MA, USA.

Al Rwahnih, M., Golino, D., Westrick, N., Diaz-Lara, A., Cooper, M., Smith, R., Battany, M., Bettiga, L., Zhuang, S., Arnold, K., Farrar, K., Rowhani, A. 2018. Field survey and molecular characterization of Californian isolates of Grapevine Pinot gris virus. Proceedings of the 19th Congress of ICVG, Santiago, Chile, 130-131.

Al Rwahnih, M. 2018. High Throughput Sequencing as a tool for viral pathogen diagnosis and expedited release of quarantined propagative plant material current prospect and challenges. Proceedings of the 19th Congress of ICVG, Santiago, Chile, 58.

Alabi, O.J., McBride, S., Appel, D.N., Al Rwahnih, M. and Pontasch, F.M., 2019. Grapevine virus M, a novel vitivirus discovered in the American hybrid bunch grape cultivar Blanc du Bois in Texas. Archives of virology, pp.1-3.

Alzubi, H., Yepes, L.M. and Fuchs, M. 2019. In vitro storage at low temperature of micropropagated grapevine rootstocks. In Vitro Cellular & Developmental Biology - Plant, 55:334-341.

Arnold, K.L., N. McRoberts, M.L. Cooper, R. Smith, D. Golino. 2019Virus Surveys of Commercial Vineyards Show Value of Planting Certified Vines. California Agriculture 73: 90-95

Beaver-Kanuya E, Harper SJ. 2019. Detection and quantification of four viruses in Prunus pollen: Implications for biosecurity. Journal of Virological Methods 271:113673

Beaver-Kanuya E, Szostek S, Harper SJ. 2019. Development of real-time RT-PCR assays for two viruses infecting pome fruit. Journal of Virological Methods 266:25-29

Chingandu, N., Jarugula, S., Movva, A. and Naidu, R.A. 2019. The occurrence of economically detrimental viruses in certified nurseries and commercial vineyards in Washington State. Washington Winegrowers Convention and Trade Show, February 12-14, 2019, Kennewick, WA, USA.

Cieniewicz, E., Flasco, M., Brunelli, M., Onwumelu A., Wise, A. and Fuchs, M.F. 2019. Differential spread of grapevine red blotch virus in California and New York vineyards. Phytobiomes, https://doi.org/10.1094/PBIOMES-04-19-0020-R

Cieniewicz, E., Wise, A., Smith, R., Cooper, M, Martinson, T. and Fuchs, M. 2019. Studies on red blotch ecology inform disease management recommendations. Wine Business Monthly, March issue, pp. 92-102.

Cieniewicz, E. J., Pethybridge, S. J., Loeb, G., Perry, K., & Fuchs, M. 2018. Insights into the Ecology of Grapevine Red Blotch Virus in a Diseased Vineyard. Phytopathology, 108, 92–102.

Cieniewicz, E., Thompson, J. R., McLane, H., Perry, K. L., Dangl, G. S., Martinson, T., Wise, A., Wallis, A. O'Connell, J., Dunst, R., Cox, K., Fuchs, M. F. 2018. Prevalence and Genetic Diversity of Grabloviruses in Free-Living Vitis spp. Plant Disease. 102:1-9.

Cieniewicz, E. and Fuchs, M. 2018. Red blotch disease ecology and management. Appellation Cornell, Research Focus, 4:1-7.

Cohen, D., Al Rwahnih, M., Chooi, K. M., Blouin, A., and MacDiarmid, R. M. 2018. Serotyping Grapevine leafroll-associated virus 3. Proceedings of the 19^th Congress of ICVG, Santiago, Chile, 138-139.

Davenport B, Li R, and Zhang S. 2019. AmplifyRP® as a direct and rapid molecular confirmation tool for lateral flow ImmunoStrip® results (poster). 2019 NPDN National Meeting, April 15-18, 2019, Indianapolis, Indiana.

Davenport B, Groth-Helms D, Li R, and Zhang S. 2019. Development of a real-time duplex isothermal assay for the detection of Tobacco rattle virus and an endogenous internal RNA control (poster 439-P2). August 3-7, 2019, 2019 APS Annual Meeting, Cleveland, Ohio.

Debat, H.J., Zavallo, D., Brisbane, R.S., Voncina, D., Almeida, R.P., Blouin, A.G., Al Rwahnih, M., Gomez-Talquenca, S. and Asurmendi, S., 2019. Grapevine virus L: a Novel Vitivirus in Grapevine. European Journal of Plant Pathology, https://doi.org/10.1007/s10658-019-01727-w

Dey, Kishore, Milena Leite, John Hu, Jordan, Ramon, and Mike Melzer 2018.  Detection of Jasmine virus H and characterization of a second pelarspovirus infecting star jasmine (Jasminum multiflorum) and angelwing jasmine (J. nitidum) plants displaying virus-like symptoms.  Archives of Virology https://doi.org/10.1007/s00705-018-3947-y

Dey, K., Melzer M., and J. Hu 2018.  Virus-Induced Gene Silencing in Plant Biotechnology,
Volume 2: Transgenics, Stress Management, and Biosafety Issues.

Dey, K, James C Green, Michael Melzer, Wayne Borth, John Hu, 2018. Mealybug Wilt of Pineapple and Associated Viruses. Horticulturae. 4:52.

Diaz-Lara, A., Klaassen, V., Stevens, K., Sudarshana, M.R., Rowhani, A., Maree, H.J., Chooi, K.M., Blouin, A.G., Habili, N., Song, Y. and Aram, K., 2018. Characterization of grapevine leafroll-associated virus 3 genetic variants and application towards RT-qPCR assay design. PloS One, 13:p.e0208862.

Diaz Lara, A., Golino, D. Al Rwahnih, M. 2018. Grapevine virus J, a novel vitivirus identified in grapevine via high-throughput sequencing. American Phytopathological Society. Boston, MA, USA.

Diaz-Lara, A., Golino, D., and Al Rwahnih, M. 2018. Genomic characterization of Grapevine virus J, a novel virus identified in grapevine. Proceedings of the 19th Congress of ICVG, Santiago, Chile, 168-169.

Druciarek, T., Lewandowski, M. and Tzanetakis I.E. 2019. First report of European mountain ash ringspot-associated emaravirus in Sorbus aucuparia in Poland. Plant Disease 103:166.

Farrar, K., Al Rwahnih, M., Byrne, D., Clark, C. A., Finch, D., Fuchs, M., Golino, D. A., Martin, R. R., Matthews, P., Nourse, N., Scott, S., Sim, S. T., Tennis, B., Vidalakis, G. 2018. The National Clean Plant Network: Improving status and availability of clean stock. American Phytopathological Society. Boston, MA, USA.

Finn, C.E., Strik, B.C., Yorgey, B.M., Peterson, M.E., Jones, P.A., Lee, J. and Martin, R.R. 2018. ‘Columbia Giant’ thornless trailing blackberry. HortScience 53:251-255.

Finn, C.E., Strik, B.C., Yorgey, B.M., Peterson, M.E., Jones, P.A., Lee, J. and Martin, R.R. 2018. ‘Columbia Sunrise’ thornless trailing blackberry. HortScience 53:256-260.

Finn, C.E., Strik, B., Mackey, T., Jones, P., Bassil, N., and Martin, R.R. 2018. ‘Echo’ ornamental reflowering blueberry.  HortScience 54:368-370.

Finn, C.E., Strik, B., Yorgey, B.M., Peterson, M.E., Jones, P.A., Lee, J., Bassil, N. and Martin, R.R. 2018. ‘Hall’s Beauty’ Thornless trailing blackberry. HortScience 54:371-376.

Fuller, K. B, Alston, J.M. and Golino, D.A.  2019. Economic Benefits from Virus Screening: A Case Study of Grapevine Leafroll in the North Coast of California.  American Journal of Enology and Viticulture 70: 139-146.

Habili, N., Wu, Q., Al Rwahnih, M., and Pagay, V. 2018. Group II variants of Grapevine virus A are associated with Shiraz Disease in Australia. Proceedings of the 19th Congress of ICVG, Santiago, Chile, 164-165.

Hadaway, K.M. Ball, T., Folwell, R., Jarugula, S. and Naidu, R.A. 2019. To test or not to test? Providing affordable diagnostic assays for the benefit of grapevine nurseries and growers. Washington Winegrowers Convention and Trade Show, February 12-14, 2019, Kennewick, WA, USA.

Hamim, I., Al Rwahnih, M., Wayne, B.B., Melzer, M.J., Gonsalves, D., Suzuki, J., Wall, M., Hu, J.S. 2018. Deep sequencing of total RNAs in papaya for genome characterization of Papaya ringspot virus Bangladesh strain. American Phytopathological Society, Boston, MA, USA.

Hamim, I., Maher Al Rwahnih, Wayne B. Borth, Jon Y. Suzuki, Michael J. Melzer, Marisa M. Wall, James C. Green, and John S. Hu. 2019. Papaya ringspot virus isolates from papaya in Bangladesh: detection, characterization and distribution. Plant Disease, in press

Hamim, I. Wayne B. Borth, Michael J. Melzer, Jon Y. Suzuki, Marisa M. Wall,·John S. Hu 2019. Occurrence of tomato leaf curl Bangladesh virus and associated subviral DNA molecules in papaya in Bangladesh: molecular detection and characterization, Archives of Virology https://doi.org/10.1007/s00705-019-04235-8

Hamim, Islam, Wayne B. Borth, Josiah Marquez, James C. Green, Michael J. Melzer, John S. Hu 2018 Transgene-mediated resistance to Papaya ringspot virus: challenges and solutions Phytoparasitica https://doi.org/10.1007/s12600-017-0636-4

Hamim, I., Wayne Borth, Michael J. Melzer, and John Hu 2018. Ultra-sensitive detection of Papaya ringspot virus using  single-tube nested PCR. Acta Virologica 62: 379 – 385.

Hassan, M., Shahid, M.S. and Tzanetakis, I.E., 2018. Molecular characterization and detection of a novel vitivirus infecting blackberry. Archives of Virology 163:2889–2893.

Hassan, M., and Tzanetakis I.E. 2019. Population structure, evolution and detection of blackberry leaf mottle associated virus, an emerging Emaravirus. Plant Pathology 68: 775-782.

Hoang, N.H., Al Rwahnih, M., Preece, J., Hsu, E., Sim, S. and Golino, D. 2018. Development of a Meristem-tip Culture Procedure for Eradication of Cherry Virus-A in Selected Cultivars of Cherry. In IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL (Vol. 54, pp. S30-S31). 233 SPRING ST, NEW YORK, NY 10013 USA: SPRINGER.

Jarugula, S., Gowda, S., Dawson, W.O. and Naidu, R.A. 2018. Development of infectious cDNA clones of Grapevine leafroll-associated virus 3 and analyses of the 5′ non-translated region for replication and virion formation. Virology 523: 89-99.

Jarugula, S., Mitra, A., Adegbola, R., Swamy, P. and Naidu, R.A. 2019^. Impacts of viral diseases in field-grafted vineyards in Washington State. 70^th American Society for Enology and Viticulture (ASEV) National Conference, June 17-20, 2019, Napa Valley, CA.

James, D., Phelan J., Sanderson, D. 2018. Blackcurrant Leaf Chlorosis Associated Virus: Evidence of the Presence of Circular RNA during Infections. Viruses 10, DOI:10.3390/v10050260

James D., Phelan, J., Sanderson, D. 2019. Detection by high throughput sequencing and molecular characterization of complexes of fabaviruses infecting Staccato® sweet cherry (Prunus aviam) in Canada. Canadian Journal of Plant Pathology https://doi.org/10.1080/07060661.2019.1566179

Jelkmann, W., Sanderson, D., Berwarth, C., James, D. 2018. First detection and complete genome characterization of a Cherry (C) strain isolate of plum pox virus from sour cherry (Prunus cerasus) in Germany. Journal of Plant Diseases 125:267-272.

Li R, Davenport B, Groth-Helms D, and Zhang S. 2019. Development of AmplifyRP assays for three important grapevine viruses through recombinase polymerase amplification (poster 434-P2). 2019 APS Annual Meeting, August 3-7, 2019, Cleveland, Ohio.

Liu H., Wu L., Nikolaeva EV, Peter K., Liu Z., Mollov D., Cao M., Li R. 2018. Characterization of a new apple luteovirus identified by high-throughput sequencing. Virology Journal 15:85

Martin, I., Vigne, E., Berthold, F., Komar, V., Lemaire, O., Fuchs, M. and Schmitt-Keichinger, C. 2018. The fifty distal amino acids of the 2A^HP homing protein of grapevine fanleaf virus elicit a hypersensitive reaction on Nicotiana occidentalis.  Molecular Plant Pathology, 19:731-743.

Martin, R.R. and Tzanetakis, I.E. 2018.  High risk blueberry viruses by region in North America; Implications for certification, nurseries, and fruit production.  Viruses 10:342 doi:10.3390/v10070342

Milusheva, S., Phelan, J., Piperkova, N., Nikolova, V., Gozmanova, M., James, D. 2019. Molecular analysis of the complete genome of an unusual virus detected in sweet cherry (Prunus avium) in Bulgaria. European Journal of Plant Pathology 153:197–207

Moore, P.P., Hoashi-Erhardt, W., Finn, C.E., Martin, R.R. and Dossett, M. 2019. ‘WSU 2166’ Red raspberry.  HortScience 54:564-567. https://doi.org/10.21723/HORTSCI13652-18.

Mitra, A., Jarugula, S., Donda, B., Jordan, E., and Naidu, R.A. 2019. Elucidating the genetic makeup of Grapevine leafroll-associated virus 3 for managing leafroll disease in Washington State vineyards. Washington Winegrowers Convention and Trade Show, February 12-14, 2019, Kennewick, WA, USA.

Naidu, R.A. 2019.  An update on grapevine viruses in Washington vineyards. G.S. Long Co., Inc. 2014 Grower Meeting, January 16, 2019, Yakima, WA.

Naidu, R.A. 2019. Current and on-going research on roguing in vineyards. Washington Winegrowers Convention and Trade Show, February 12-14, 2019, Kennewick, WA, USA.

Nikolaeva E.V., Peter K.A., Jones T., Knier R., C. Molnar. 2019. Pennsylvania Orchard survey for Rapid Apple Decline. 2019. Phytopathology, in press

Osterbaan, L. and Fuchs, M. 2019. Dynamic interplays between plant virus and their host interactants for symptom development. Journal of Plant Pathology, https://doi.org/10.1007/s42161-019-00323-5

Osterbaan, L.J., Choi, J., Kenney, J., Flasco, M., Vigne, E., Schmitt-Keichinger, C., Rebelo, A.R., Heck, M. and Fuchs, M. 2019. The identity of a single residue of the RNA-dependent RNA polymerase of grapevine fanleaf virus modulates vein clearing symptoms in Nicotiana benthamiana. Molecular Plant-Microbe Interactions, 32:790-801.

Osterbaan, L., Schmitt-Keichinger, C. Vigne, E. and Fuchs, M. 2018. Optimal systemic grapevine fanleaf virus infection in Nicotiana benthamiana following agroinoculation. Journal of Virological Methods, 257:16-21.

Pallás, V., Sánchez-Navarro, J., James, D. 2018. Recent advances on the multiplex molecular detection of plant viruses and viroids. Frontiers in Microbiology https://doi.org/10.3389/fmicb.2018.02087

Perry, K. L., McLane, H., Thompson, J. R., & Fuchs, M. 2018. A novel grablovirus from non-cultivated grapevine (Vitis sp.) in North America. Archives of Virology, 163:259–262.

Pinon, A.F. and Martin, R.R. 2018. Frist report of strawberry necrotic shock virus in strawberry in Benquet, Philippines. Plant Disease 102:2385. https://doi.org/10.1094/PDIS-03-18-0491-PDN

Rasool, S., Naz, S., Rowhani, A., Diaz-Lara, A., Golino, D.A., Farrar, K.D. and Al Rwahnih, M., 2019. Survey of grapevine pathogens in Pakistan. Journal of Plant Pathology, https://doi.org/10.1007/s42161-019-00263-0

Romero, J. L. R., Carver, G. D., Johnson, P. A., Perry, K. L., and Thompson, J. R. 2019. A rapid, sensitive and inexpensive method for detection of grapevine red blotch virus without tissue extraction using loop-mediated isothermal amplification. Archives of Virology. 164:1453–1457.

Rott, M., Kesanakurti, P., Berwarth, C., Rast, H., Boyes, I., Phelan, J., Jelkmann, W. 2018. Discovery of Negative-Sense RNA Viruses in Trees Infected with Apple Rubbery Wood Disease by Next-Generation Sequencing. Plant Disease DOI:10.1094/PDIS-06-17-0851-RE

Sanderson, D., James D. 2019. Analysis of the genetic diversity of genome sequences of isolates/variants of apple hammerhead viroid. Canadian Journal of Plant Pathology DOI: 10.1080/07060661.2019.1614672

Serra, P., Messmer, A., Sanderson, D., James, D., Flores, R. 2018. Apple hammerhead viroid-like RNA is a bona fide viroid: Autonomous replication and structural features support its inclusion as a new member in the genus Pelamoviroid. Virus Research 249:8-15

Setiono, F. J., Chatterjee, D., Fuchs, M., Perry, K. L., & Thompson, J. R. 2018. The distribution and detection of grapevine red blotch virus in its host depends on time of sampling and tissue type. Plant Disease. 102:2187-2193.

Sim, S.T., Khuu, N., Shoulders, J.R., Pudlo, W., Hoang, N.H. and Golino, D.A. 2019.  Elimination of rose viruses using microshoot tip tissue culture. Acta Hortic. 1232:241-246

Sinha, R., Khot, L.R., Rathnayake, A.P., Gao, Z. and Naidu, R.A. 2019. Visible-near infrared spectroradiometry-based detection of grapevine leafroll-associated virus 3 in a red-fruited wine grape cultivar. Computers and Electronics in Agriculture 162: 165-173.

Thekke-Veetil, T., Ho, T., Postman, J.D., Martin, R.R. and Tzanetakis, I.E. 2018. A virus in American blackcurrant (Ribes americanum) with distinct genome features reshapes classification in the Tymovirales. Viruses 10:342 

Thompson, B.D., Dahan, J., Lee, J., Martin, R.R. and Karasev, A.V. 2019. A novel genetic variant of Grapevine leafroll-associated virus-3 (GLRaV-3) from Idaho grapevines. Plant Disease 103:509-518. 

Tzanetakis, I.E. and Martin R.R. 2019. Improving plant propagation methods for fruit disease control, in Integrated management of insect pests and diseases of tree fruit (Ed. X. Xu and M.  Fountain, Burleigh Dodds, pp14, in press

Vargas-Asencio, J., Liou, H., Perry, K. L., and Thompson, J. R. 2019. Evidence for the splicing of grablovirus transcripts reveals a putative novel open reading frame. Journal of General Virology. 100:709–720.

Villamor, D.E., Ho, T., Al Rwahnih, M., Martin, R.R. and Tzanetakis, I.E., 2019. High Throughput Sequencing in Plant Virus Detection and Discovery. Phytopathology 109: 716-725.

Wang, D., I. Hamim, J. C. Green, W. B. Borth, M. J. Melzer, and J. S. Hu, 2018.  First Report of Dasheen mosaic virus infecting Taro (Colocasia esculenta) in Bangladesh. Plant Disease https://doi.org/10.1094/PDIS-03-18-0442-PDN.

Wang, D., Ocenar^, J., I. Hamim, J. C. Green, W. B. Borth, M. J. Melzer, Suzuki, J., M. M. Wall, M.M., Matsumoto, T., G. F. Sun, and J. S. Hu, 2018.   First Report of Bean yellow mosaic virus Infecting Nasturtium (Tropaeolum majus) in Hawaii.  Plant Disease  https://doi.org/10.1094/PDIS-06-18-1082-PDN.

Wang, D., I. Hamim, J. C. Green, W. B. Borth, M. J. Melzer, Suzuki, J., M. M. Wall, M.M., Matsumoto, T., G. F. Sun, and J. S. Hu, 2018.  First Report of Apple of Peru (Nicandra physalodes) Infected with Pepper mottle virus in Hawaii. Plant Disease  https://doi.org/10.1094/PDIS-06-18-1061-PDN.

Weiland, J.E., Benedict, C., Zasada, I.A., Scagel, C.R., Beck, B.R., Davis, A., Graham, K., Peetz, A., Martin, R.R., Dung, J.K.S., Gaige, A.R. and Thiessen, L. 2018. Late summer disease symptoms in western Washington red raspberry fields associated with co-occurrence of Phytophthora rubi, Verticillium dahliae, and Pratylenchus penetrans, but not Raspberry bushy dwarf virus.  Plant Disease 102:938-947.

Wright AA, Szostek S, Harper SJ. 2018. Diversity of three bunya-like viruses infecting apple. Archives of Virology 163:3339–3343

Wu, L., Liu, H., Postman, J.D., Li, R. 2018. Molecular characterization of a novel nucleorhabdovirus from black currant identified by high-throughput sequencing. Archives of Virology https://doi.org/10.1007/s00705-018-3709-x.

Xiao, H., Li, C., Al Rwahnih, M., Dolja, V. and Meng, B., 2019. Metagenomic Analysis of Riesling Grapevine Reveals a Complex Virome Including Two New and Divergent Variants of Grapevine leafroll-associated virus 3. Plant Disease 103:1275-1285.

Xue Feng, Gardenia E. Orellana, James C Green, Michael J. Melzer, John S. Hu and Alexander V. Karasev, 2019. A New Strain of Bean Common Mosaic Virus From Lima Bean (Phaseolus lunatus); Biological and Molecular Characterization. Plant Disease https://doi.org/10.1094/PDIS-08-18-1307-RE

Yepes, L., Cieniewicz, E. J., Krenz, B., McLane, H. M., Thompson, J. R., Perry, K. L. and Fuchs, M. 2018. Causative role of grapevine red blotch virus in red blotch disease. Phytopathology 108:902-909.

Yepes, L.M., Burr, T.J., Reid, C. and Fuchs, M. 2019. Elimination of the crown gall pathogen, Agrobacterium vitis, from systemically infected grapevines by tissue culture. American Journal of Enology and Viticulture, 70:243-248.

Zhang, J., Borth, W.B., Sether, D., Lin, B, Melzer, M.J., Shen, H., Pu, X, Sun, D., Nelson, S., Hu, J.S. 2018. Multiplex Detection of Three Banana Viruses by Reverse Transcription Loop-mediated Isothermal Amplification (RT-LAMP). Tropical Plant Pathology 43:543–551.

Zhang, J., John Hu, Huifang Shen, Yucheng Zhang, Dayuan Sun, Xiaoming Pu, Qiyun Yang, Qiurong Fan and Birun Lin. 2018. Genomic analysis of the Phalaenopsis pathogen Dickeya sp. PA1, representing the emerging species Dickeya fangzhongdai.  BMC Genomics (2018) 19:782 https://doi.org/10.1186/s12864-018-5154-3

Zheng, L., Wu, L., Postman, J.D., Liu, H., Li, R. 2018. Molecular characterization of a novel closterovirus identified from blackcurrant by high-throughput sequencing. Archives of Virology. https://doi.org/10.1007/s11262-018-1598-4.

Zurn, J.D., Ho, T., Li, R., Bassil, N.V., Tzanetakis, I.E., Martin, R.R. and Postman, J.D. 2019.  First report of blackcurrant reversion virus in Ribes nigrum germplasm in the United States. Plant Disease, 103:1051.