Progress 07/01/10 to 06/30/15
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Two undergraduate students from Washington universities and colleges were employed during the past year. They gained experience and exposure to agricultural research and molecular sciences as well as direct interaction with the grower community. Additionally, one Research Associate and one Post-Doctoral Research Associate were employed in the program where they received training and exposure to project development and management. The Clean Plant Center Northwest provides an opportunity to become familiar with quarantine and trade issues associated with international and domestic movement of planting stock. How have the results been disseminated to communities of interest?Research reviews sponsored by specialty crop producers are an important method of disseminating current information about virus diseases and their management. During this period, members of this project presented at four different research reviews that draw significant participation from the grower communities. The clean plant program mission and operations were presented at three large regional agricultural meetings and trade shows. The programs were also presented to a group of international students representing promising leaders in agriculture from several different countries. Two full length journal articles appeared in professional scientific journals frequently used by the relevant research communities. What do you plan to do during the next reporting period to accomplish the goals?Representative samples from commercial production areas will be evaluated for the presence of new viruses. This is critical to help define future regulatory actions. The data will also provide some insight into the origina of the viruses and the potential economic impact. The service-oriented activities of the project continue to expand to meet industry demands. Activities need to be strategic to continue to provide services with available resources.
Impacts
What was accomplished under these goals?
Goal 1 Nectarine selections showing stem-pitting symptoms on the woody cylinder above the graft union were observed and suspected to be infected by a virus or virus-like agents. However, the current approved standards for fruit tree pathogen detection, which includes a panel of molecular, serological and biological tests, failed to identify any virus or virus-like agents or phytoplasma in the affected symptomatic trees. These trees were then subjected to high throughput sequencing and the results revealed the presence of two novel virus-like sequences in the symptomatic trees corresponding to lutoeviruses and marafiviruses. The graft transmissibility of these two viruses was demonstrated, thereby confirming the viral nature of the sequences. Further insights onto this stem pitting disease of nectarine suggested that the disease may be a reaction only of specific nectarine genotypes upon infection by these two viruses, or a phenotypic expression of a group nectarine genotypes sharing common parentage. This supposition is based on the further identification of a non-symptomatic nectarine (no stem pitting) that is infected by the same viruses. The potential role of the tree genotype is further supported by the revelation that all the virus-infected symptomatic nectarines share a common parent. The etiology of this disease is currently under investigation. Molecular assays (RT-PCR) were developed for the luteo- and marafi-viruses infecting fruit trees and incorporated into the current testing procedure. Little cherry disease reached significant proportions in some sweet cherry orchards of Washington State during the previous three growing seasons. Based on previous work, it became evident that Little cherry virus 2 was a major factor in the disease outbreak. However, through testing of samples with characteristic field symptoms of little cherry disease, 39% of the diseased trees were infected with Western X phytoplasma, another agent associated with little cherry disease. In response, the development of a recombinase polymerase amplification (RPA) assay for Western X was completed. Test results with this method are consistent with PCR assay results. Tissue type and time of sampling were investigated. Leaf tissue and cambial scrapings were the most reliable, and sampling starting at harvest time provided dependable assay results for the Western X phytoplasma. In a small number of cases (less than 4%) of trees exhibiting little cherry disease, the commercially available RT-RPA assay system and PCR for Western X failed to yield positive reactions. Subsequent sequence analysis revealed that an uncommon strain of Little cherry virus 2 was the pathogen responsible for disease. Additional sequence information was obtained and the RT-RPA for Little cherry virus 2 was modified to detect this novel strain as well as the standard strains. Goal 2) High throughput sequencing was investigated as a diagnostic tool to enhance the delivery of virus-tested fruit tree, grapevine and hop plant selections to industry while maintaining high phytosanitary standards. High throughput sequencing for pathogen detection was assessed over a three year period in the foundation fruit tree program. In every case, high throughput sequencing revealed virus(es) that corresponded to viruses detected by existing protocols that are combination of molecular, serological and biological assays. , high throughput sequencing also successfully revealed the presence of virus. In addition to the novel luteo- and marafi- viruses in nectarine stem pitting samples, high throughput sequencing further revealed the presence of additional novel virus sequences in Prunus species that were not revealed by "conventional" diagnostic methods. It was demonstrated that these agents are graft transmissible, thus confirming that these sequences are associated with biotic agents rather than host sequence. High throughput sequencing was also used to corroborate the virus status of vines established in the grapevine foundation program. RNA was extracted from 60 selections and subjected to high throughput sequencing. The results revealed the presence of Hop stunt viroid, Grapevine yellow speckle viroid-1 and Grapevine yellow speckle viroi-2. Viroids are not excluded from the existing grapevine foundation program so their occurrence was anticipated. However, the results also revealed the presence of two marafiviruses namely, Grapevine Rupestris vein feathering virus and Grapevine Syrah virus 1. Testing for these two viruses was not part of the original virus testing procedure for grapevines. However, their detection by high throughput sequencing in a few selections resulted in tests for these viruses being incorporated standard testing procedures. Aside from viruses and viroids, fastidious bacteria such as phytoplasma are also included tests in the current accepted standard for fruit tree pathogen certification. Like DNA viruses, detecting phytoplasma by deep sequencing of RNA is also uncertain since only expressed portions of the genome are detected in this manner. Total RNA from Western X phytoplasma infected sweet cherry and pear decline phytoplasma infected pear trees were sent for deep sequencing. Although the entire genome of each phytoplasma was not recovered using this approach, sufficient sequence information was available that resulted in the positive identification of the corresponding phytoplasma in each sample. The program reduces the impact of viruses and virus-like agents on the economic viability of U.S. producers by distributing virus-tested material that is multiplied further in the nation's nursery system. During this reporting period, the fruit tree program received 123 selections from foreign sources and 83 selections from within the U.S. These are virus tested and subjected to virus elimination as needed. Approximately 40% of the selections entering the program are virus infected. By distributing propagation material after virus-elimination, the burdern of viruses on U.S. production is substantially reduced. During this period, 7,2015 buds from 186 different fruit tree selections were distributed. Similarly, the grape foundation program distributed 6,485 dormant cuttings to growers and nurseries, primarily to producers of certified grapevines in the Pacific Northwest. The hop foundation program distributed 25 established potted plants and 1,221 green cuttings to producers and propagators.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Gergerich RC, Welliver RA, Gettys S, Osterbauer NK, Kamenidou S, Martin RR, Golino DA, Eastwell K, Fuchs M, Vidalakis G, Tzanetakis IE. 2015. Safeguarding Fruit Crops in the Age of Agricultural Globalization. Plant Disease 99:176-187.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Villamor DEV, Susaimuthu J, Eastwell KC. 2015. Genomic analyses of cherry rusty mottle group and cherry twisted leaf associated viruses reveal a possible new genus within the family Betaflexiviridae. Phytopathology 105:399-408.
|
Progress 10/01/13 to 09/30/14
Outputs
Target Audience: The program provides information exchange, services and research directed to nurseries, breeding programs, regulatory agencies, growers, crop consultants and other stakeholders involved in the production of vegetatively propagated perennial specialty crops around the world. The program provides valuable research and outreach activities to serve the National Clean Plant Network. The project provides mentoring, training to graduate students in Plant Pathology, and international scientists and students. Changes/Problems: The absence of Farm Bill funding during the year hampered our ability to execute the service activities associated with this project. It affected our ability to retain staff and to follow planned and necessary modifications to operations. What opportunities for training and professional development has the project provided? Four undergraduate students from Washington universities and colleges were employed during the past year. They gained experience and exposure to agricultural research and molecular sciences as well as direct interaction with the grower community. Additionally, one Post-Doctoral research associate was employed in the program where he received training and exposure to project development and management. Participating in the operation of the quarantine facility and the international exchange of propagation material provides a unique opportunity for students and professionals to become familiar with this exclusive side of international agriculture and trade. How have the results been disseminated to communities of interest? The developments in fruit tree virus detection and management were reported at 17 research reviews and stakeholder-sponsored meetings of growers, regulatory agencies and granting agencies during the reporting period. The fruit tree program was represented by a display booth and oral presentation at the Washington State Horticultural Society trade show and meeting in Kennewick, WA. Fact sheets describing the symptoms and management of little cherry disease were distributed at these forums and distributed to extension offices in Washington State. Presentations by the PI and an online video presentation prepared by Good Fruit Grower Magazine raised awareness of the impact of virus on orchard productivity. Activities of the grapevine foundation program were reported at the region's largest wine grape growing trade show and a display booth was presented promoting the use of clean planting stock in vineyard establishment. A training session for vineyard workers was organized by the wine grape producers and the Clean Plant Center Northwest program was featured as one of the key elements for successful grape cultivation. Similarly, activities of the hop foundation program were presented at national meetings attended by growers, brokers and brewers. The Clean Plant Center Northwest established a web site that provides information on the programs and its products, as well as reference material for disease recognition. The CPCNW hosted two student groups with interest in plant pathology to explain the basics of plant quarantine systems and the advanced technology be used to implement them. Two full length journal articles and two brief reports appeared in professional scientific journals frequently used by the relevant research communities. Progress in characterizing viruses associated with diseases withpreviously unknown etiology was reported to the specialized audience of WERA-020. What do you plan to do during the next reporting period to accomplish the goals? Investigation of vector transmission of the newly described viruses will be initiated based on affinity of the viruses for known virus genera. Research is continuing on the development and refinement of improved diagnostic methods for field applications as well as the use of advanced tools in molecular biology to identify novel pathogens in the quarantine environment. The service-oriented activities of the project will continue, depending on availability of external funding sources. To better achieve this objective a review and strategic planning process will be executed. Program staff will be engaged in numerous meetings of growers and regulatory agencies to provide the most current information on virus diseases and management, and the benefits of using clean planting stock.
Impacts
What was accomplished under these goals?
Goal 1a) The rusty mottle group of diseases of sweet cherry consists of a collective of diseases that have a significant negative impact on cherry production. Similarly, cherry twisted leaf and apricot ringpox diseases are associated with the production of poor quality fruit. The complete genomic sequences of viruses associated with these disease groups were determined. These sequences, in combination with previously reported virus sequences from cherry trees, delimit a new genus of viruses within the family Betaflexiviridae. This taxonomic structure is based on host range, symptomatology and genome organization. The results give valuable insight into the relationships between viruses causing several important diseases of cherry. The identification of virus species associated with each disease and their sequences enabled the development of molecular assays for each of the viruses. As a result, it is now possible to diagnose the causal agents of disease in production orchards more quickly and reliably than was possible previously. Thus, time and resources are not expended in efforts to correct horticultural problems in commercial orchards where a viral agent is the root cause of poor orchard performance. Moreover, quicker detection and diagnosis permits better containment of virus as infected trees can be removed quickly from the commercial orchard. Virus-specific assays are also of value in the quarantine program to verify results from biological assays that are often ambiguous. Consequently, more reliable information regarding the phytosanitary status of trees in quarantine and foundation programs is provided so that unnecessary virus elimination therapy based on equivocal biological assays is prevented. Goal 1b) Little cherry disease caused by Little cherry virus 2 has caused significant losses to cherry production west of the continental divide since the early 1930s. The Washington State industry experienced a resurgence of the disease in 2010 resulting in the removal of hundreds of acres of sweet cherry trees. At least three biotic agents as well as many horticultural factors are associated with the development of small fruit. Consequently, correct identification of the causal agent is critical in order to implement appropriate response measures. In a collaborative project with a private company, newly developed technology was applied to the detection of Little cherry virus 2. The reverse transcription recombinase polymerase amplification assay (RT-RPA) technology permits diagnosis of virus sequences in an isothermal reaction without specialized equipment. However, through application of this new technology, it became apparent that a small number of infected trees did not respond in the new assay system, and yet were positive using other diagnostic methods. Sequencing segments of the aberrant isolates revealed the presence of a distinct isolate of Little cherry virus 2 that had not been previously reported in the Pacific Northwest. This sequencing data as well as additional information obtained through deep sequencing and the public database are used to redesign the assay system. During the course of research to characterize the pathogens associated with little cherry disease in central Washington, it became evident that a significant number of trees were infected with Western X phytoplasma, another causative agent associated with little cherry disease. Trees infected with Western X phytoplasma were subjected to deep sequencing in order to obtain regions of sequence identity between published phytoplasma sequences and those sequences from regional isolates. Regions of identity were used to design primers and probes for prototype RPA reagents. Goal 2a) Rapid access to newly developed clones is essential for U.S. specialty crop industries to remain competitive in the global market. Deep sequencing is being explored as a diagnostic procedure to enhance the delivery of virus-tested fruit tree, grapevine and hop plant selections to their respective industries. It is anticipated that adoption of this technology will provide more accurate diagnosis and reduce the residency time of fruit trees in quarantine by one year, allowing more rapid introduction of new selections from foreign breeding programs into the U.S. A critical component of virus diagnosis using deep sequencing is establishing parameters for analysis that establish a meaningful balance between the need to acquire valid results and the demands on computational resources. Deep sequencing was assessed over a period of three years for virus detection in the foundation fruit tree program. In every case where a virus was detected by existing diagnostic protocols that are combination of molecular, serological and biological assays, deep sequencing also successfully revealed the presence of virus. Additionally, the use of deep sequencing revealed the presence of three novel virus sequences in Prunus species that were not revealed by "conventional" diagnostic methods. It was confirmed that these agents are graft transmissible, thus confirming that these sequences are associated with biotic agents rather than host sequence. The availability of the sequence information obtained during this project also enabled the development of molecular assays (reverse transcription polymerase chain reaction or RT-PCR). These assays are being used to screen the foundation collection of virus-tested trees. Biological characteristics of these new viruses are under investigation. Deep sequencing was used as a tool to validate the accuracy of protocols for virus detection established for the grapevine foundation program. Thirty grapevine selections from various origins that had been subjected to microshoot tip culture followed by virus testing were selected from the foundation vineyard. RNA was extracted and subjected to deep sequencing. The results confirmed the presence of Hop stunt viroid, Grapevine yellow speckle virus-1 and Grapevine yellow speckle virus-2. Viroids are not excluded from the existing grapevine foundation program so their occurrence was anticipated. However, one selection also contained Rupestris stem pitting associated virus. Based on sequence information obtained during deep sequencing, this isolate would not have been detected by the RT-PCR methods previously used in the program because of sequence variation, but it would be detected by the current primers selected for RT-PCR. Two viruses of grapevines have been recently described that contain DNA as their genetic information. Protocols and known infected samples of grapevine vein clearing virus and grapevine red-blotch associated virus were obtained from the foundation programs at the University of Missouri (W. Qiu) and University of California, Davis (M. Al Rwahnih), respectively. The protocols were successfully adapted to the procedures and instrumentation currently in use at the Clean Plant Center Northwest. One grapevine in the foundation vineyard was detected with grapevine vein clearing virus. It was a recent introduction and was promptly removed from the vineyard once the results were confirmed. Since these are DNA containing viruses, it was uncertain whether deep sequencing of RNA isolated from the grapevines would reveal the presence of the virus. Since only expressed portions of the genome are detected in this manner, the entire genome sequence was not obtained, however sufficient sequence information was present in the output to easily identify the presence of this virus in the sample. The results of these experiments demonstrate the power of deep sequencing for virus diagnostics, particularly for the detection of viruses that are not well characterized. Further validation is required to gain wide acceptance of this technology for quarantine and trade purposes.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Villamor DEV, Susaimuthu J, Eastwell KC. 2014. Genomic analyses of cherry rusty mottle group and cherry twisted leaf associated viruses reveal a possible new genus within the family Betaflexiviridae. Phytopathology DOI: 10.1094/PHYTO-03-14-0066-R
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Mekuria, TA, Zhang S, Eastwell KC. 2014 Rapid and sensitive detection of Little cherry virus 2 using isothermal reverse transcription-recombinase polymerase amplification. Journal of Virological Methods 205:24-30.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Akinbade SA, Mojtahedi H, Guerra L, Eastwell K, Villamor DEV, Handoo ZA, Skantar AM. 2014. First Report of Xiphinema rivesi (Nematoda, Longidoridae) in Washington State. Plant Disease 98: 1018.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Villamor DEV, Ward KF, Collman SJ, Eastwell KC. 2014. First Report of Infection of Cherry Rusty Mottle Associated Virus in Portuguese Laurel (Prunus lusitanica) in Washington State. Plant Disease 98: 699.
|
Progress 01/01/13 to 09/30/13
Outputs
Target Audience: The program provides information exchange, services and research directed to nurseries, breeding programs, regulatory agencies, growers, crop consultants and other stakeholders involved in the production of vegetatively propagated perennial specialty crops around the world. The program provides valuable research and outreach activities to serve the National Clean Plant Network. The project provides mentoring, training to graduate students in Plant Pathology, and international scientists and students. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? During 2013, two post-doctoral research positions and two doctoral students were hosted in the project. This program provides experience in both advanced molecular diagnostic methods, and direct interaction with segments of the industry affected by virus diseases. The quarantine facility associated with the project provides exposure to issues encountered in the international movement of plant material. How have the results been disseminated to communities of interest? 07/24/2013; Washington Tree Fruit Research Commission Technology Review 03/07/2013; California Department of Food and Agriculture Industry Advisory Board 04/09/2013; Washington Hop Commission 10/16/2013; Washington Tree Fruit Research Commission Cherry Research Review 11/12/2013). Practical implications of the research from this program were presented at Hop Growers of America (01/24/2013) and at an orchard demonstration session attended by 20 growers and fieldmen (07/19/2013). Presentations and a field tour were provided to the WERA-020 study group (09/10-12/2013) that includes scientists and regulatory specialists. The WERA-020 sessions provided current information to participants about trends in disease management. In addition to these meetings, 22 visits to individual orchards provided growers with assistance in disease diagnosis and site-specific disease management measures. The use of clean planting stock has been encouraged through display booths at the Washington Association of Wine Grape Growers Annual Meeting and Trade Show (02/03-08/2013), and the Washington State Horticultural Association Annual Convention (12/01-03/2013). What do you plan to do during the next reporting period to accomplish the goals? The service activities of the project will continue, depending on availability of external funding sources. Research is continuing on the development and refinement of improved diagnostic methods for field applications. Advanced tools in molecular biology are being used to identify novel pathogens, and to document the impact of plant pathogen infection on plant metabolism. Program members will be engaged in numerous grower meetings to provide them with the latest information regarding the outbreak of little cherry disease in the PNW, and the benefits of using clean planting stock.
Impacts
What was accomplished under these goals?
Objective 1: Characterize causal agents associated with graft-transmissible diseases of unknown etiology of targeted diseases. b) Development of rapid diagnostic tools to assess the disease status of horticultural crops. Significant progress was made in the identification of disease agents that infect perennial specialty crops (Objective 1a). The rusty mottle group of diseases of sweet cherry is a complex of diseases that elicit characteristic symptoms on specific cherry cultivars. The presumptive identities of the viruses associated with the diseases in this complex were identified through this project. The virus associated with cherry rusty mottle disease was characterized for the first time, and the association of Cherry necrotic rusty mottle virus with cherry necrotic rusty mottle disease was confirmed. These viruses are distinct virus species and related to the previously identified Cherry green ring mottle virus. Additional sequence analysis revealed that viruses associated with cherry twisted leaf and apricot ringpox diseases are also related. Collectively, these viruses appear to define a distinct genus of viruses based on host range, genome organization and symptomatology. This information provides much clearer relational information about these diseases and their causal agents, and provides the basis for developing more rapid and reliable diagnostic methods (Objective 1b). The development of fruit symptoms associated with apple green crinkle disease is weather dependent. Consequently, the current orchard-based assays are dependent on appropriate but still ill-defined weather conditions during the three-year assay period. The association between disease and specific virus symptoms were established for the first time. Research continues to substantiate these preliminary observations, and if successful, the ability to reliably monitor and eliminate this disease from fruit planting stock will be attainable (Objective 1b). Biological data suggested that the causal agent of peach wart disease is a strain of Cherry mottle leaf virus. Using advanced molecular tools, this relationship was confirmed. This association can be used to predict the behavior of peach wart disease based on extensive studies that were previously conducted on Cherry mottle leaf virus. Without knowledge of the agents associated with disease, the detection of disease agents often requires biological indexing that is costly and very time consuming. It is challenging to provide the facilities and expertise needed to conduct the testing. More importantly however, the biological assays require several years to complete the test, delaying access by the industry to virus-free planting material. Therefore, determination of disease causing agents leads to more rapid and reliable detection methods that facilitate research and development of disease management options. Objective 2: Develop appropriate control measures to minimize the economic impact of viruses to perennial specialty crops. a) Provide safe and efficient development of propagation material representing commercially relevant clones of perennial specialty crops that are free of targeted pathogens. b) Evaluate the response of prospective new rootstocks and cultivars to agents commonly found in U.S. perennial crop sector. c) Develop and promote strategies to reduce the economic impact of targeted pathogens. A major component of this project is the development of appropriate control measures to minimize the economic impact of virus-like agents to perennial specialty crops. This is achieved, in part, by providing virus-tested propagation material of temperate climate fruit and nut trees, grapevines and hop plants for use by the perennial specialty crops industries of the U.S. (Objective 2a). This service activity, as described elsewhere, has been very effective and very active in distributing healthy planting stock to nursery- and state-operated certification programs that subsequently expand the material to produce millions of healthy trees. Effective control of virus diseases (Objective 2c) also requires basic epidemiological information. A natural infection of an ornamental host of Cherry rusty mottle-associated virus was identified. Thus, this ornamental host (Prunus lusitanica) could provide inoculum for this virus in commercial fruit producing areas. The means by which this virus is transmitted is still unknown. Awareness of little cherry disease caused by Little cherry virus 2 has increased dramatically in several counties of Washington State. The known vector for this virus, apple mealybug, is relatively uncommon in these areas. However, this project identified grape mealybug as an additional vector of Little cherry virus 2. Populations of this insect have increased in the Pacific Northwest over the past decade; this may account for the sudden increase in reported incidence of the disease. This vector is not normally considered an economic pest, but now that its potential to spread disease is known, producers will take more aggressive action against the insect to slow the further spread of disease.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Villamor DE, Druffel KL, Eastwell KC. 2013. Complete nucleotide sequence of a virus associated with rusty mottle disease of sweet cherry (Prunus avium). Archives of Virology 158:18051810.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
James D, Varga A, Jesperson GD, Navratil M, Safarova, D, Constable F, Horner M, Eastwell K, Jelkmann W. 2013. Identification and complete genome analysis of a virus variant or putative new foveavirus associated with apple green crinkle disease. Archives of Virology 158:18771887
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Mekuria T, Smith TJ, Beers EH, Eastwell KC. 2013. Little cherry virus 2 is transmitted to sweet cherry by Pseudococcus maritimus (Ehrhorn), a new vector of this virus. Plant Disease 97:851.
- Type:
Book Chapters
Status:
Published
Year Published:
2013
Citation:
Diseases caused by viruses. 2013. Compendium of Apple and Pear Diseases and Pests, Second Edition. T. Sutton, H. Aldwinkle, A.M. Agnello, J.F. Walgenbach, Agenllo A. 2013, Ed. APS Press. ISBN 978-0-89054-430-3
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Mekuria T, Druffel KL, Susaimuthu J, Eastwell KC. 2013. Complete nucleotide sequence of a strain of Cherry mottle leaf virus associated with peach wart disease in peach. Archives of Virology 158:2201-2203 .DOI 10.1007/s00705-013-1698-3
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Villamor DE, Susaimuthu J, Eastwell KC. 2013. Viruses associated with cherry twisted leaf and the rusty mottle group of diseases of sweet cherry represent distinct species within the family Betaflexiviridae. Phytopathology Accepted July 2, 2013.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2014
Citation:
Villamor DEV, Ward KF, Collman SJ, Eastwell KC. 2013. First Report of Infection of Cherry Rusty Mottle associated virus in Portuguese Laurel (Prunus lusitanica) in Washington State. Plant Disease.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2014
Citation:
Akinbade SA, Mojtahedi H, Guerra L, Eastwell K, Villamor DEV, Handoo ZA, Skantar AM. 2013. First report of Xiphinema rivesi (Nematoda, Longidoridae) in Washington State. Plant Disease.
|
Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: An outbreak of Little cherry virus 2 in the Pacific Northwest became evident in 2010. Grape mealybug (Pseudococcus maritimus) is increasingly evident in fruit tree orchards of the Pacific Northwest but is rarely an economic pest in stone fruits. Apple mealybug (Phenacoccus aceris) is known to transmit Little cherry virus-2, so the role of grape mealybug as a vector of little cherry disease was examined. After a seven day acquisition period and a seven day transmission period, grape mealybug transmitted Little cherry virus-2 to 80% of 'Bing' cherry trees. Therefore, the increasing presence of grape mealybug in stone fruit orchards may contribute to the increased incidence of little cherry disease. Through presentations to growers and orchard managers, the industry has become aware that little cherry disease may be the cause of poor productivity and is seeking confirmation through laboratory tests. Consequently, many more infected trees are being detected and removed. Cherry leaf roll virus persists in sweet cherry in Washington State. Root grafting is an important mode of transmission within the orchard. Field trials demonstrate that the cherry rootstock 'Colt' reacts to cherry leaf roll virus with a hypersensitive response thus preventing virus transmission through root grafting. Once a scion growing on 'Colt' rootstock becomes infected, the hypersensitive reaction at the graft union leads to a quick decline of the tree and quickly eliminates potential infection sources. The trial continues to identify other rootstocks that could limit the spread of cherry leaf roll and provide good horticultural properties for growers. The complete genome of the sweet cherry isolate of cherry leaf roll virus was determined. Both RNAs of the bipartite genome contain 657 nucleotides at the 5'-terminus that are 99% identical. This region includes the 5'-UTR and also encodes the first 214 amino acids of the polyproteins encoded by RNA1 and RNA2. This unusual arrangement is shared only with the rhubarb strain of cherry leaf roll virus and with tomato ringspot virus. Cherry leaf roll virus has been detected in rhubarb and elderberry in Washington State, but sequence analysis indicates that these are not the same isolates that occur in cherry. Sequences from the coat protein coding sequence from the rusty mottle group of cherry viruses were resolved into a distinct population within the unclassified Betaflexiviridae. A virus sequence specifically associated with cherry rusty mottle disease was identified and sequence analysis suggests that it is a new virus species. The complete genomic sequence of American hop latent virus (AHLV; genus Carlavirus) was determined. The genome of 8,601 nucleotides potentially encodes six ORF in the positive sense; their organization is typical of other carlaviruses. The coat protein coding sequence of AHLV is only remotely related to the other carlavirus sequences known to infect hop. Polyclonal antibodies were produced against the bacterially expressed coat protein of AHLV and in ELISA, they differentiated between AHLV and other carlaviruses of hop. PARTICIPANTS: Kenneth C. Eastwell, Professor, Department of Plant Pathology and Director, National Clean Plant Network for tree fruit, grape and hop TARGET AUDIENCES: This project is targeted to improve the economic sustainability of producers of perennial specialty crops that are propagated vegetatively. Viruses and virus-like agents can have a devastating impact on farm income because the impacts of disease are evident year after year, until the planting is removed. The main benefactors of this project are the nurseries that produce planting stock and the growers that ultimately depend on the yield from that planting stock. Maximizing production while minimizing production costs associated with crop losses caused by viruses benefits all U.S. consumers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Identification of the causal agent and the vector associated with the recent resurgence of little cherry disease allowed growers to respond proactively to minimize the spread of the disease and its continued impact on production. The availability of rootstocks that stop the spread of cherry leaf roll virus provides a valuable tool to producers of seedling rootstock and vegetative propagation units. The rapid decline of infected trees significantly reduces the risk of inadvertent propagation of infected material, and eliminates the financial burden of proactive testing by laboratory methods every year. Identification of the causal agent of rusty mottle disease provides the basis for developing a diagnostic method that will allow growers to identify the source of poor productivity in their orchards. Access to relatively inexpensive diagnostic tests for American hop latent virus allows growers to test individual plants before hop plants are propagated for expansion of plantings. This reduces the impact of this virus on production, particularly in the first years when as a new planting becomes established.
Publications
- Eastwell K.C., T. Mekuria, K.L. Druffel, 2012. Complete nucleotide sequences and genome organization of a cherry isolate of Cherry leaf roll virus. Archives of Virology. 157(4):761-764.
- Eastwell K.C., K.L. Druffel. 2012. Complete genome organization of American hop latent virus and its relationship to carlaviruses. Archives of Virology. 157:1403-1406.
|
Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: In 1999, we discovered that cherry leaf roll virus was contributing to the decline of cherry trees in WA State. The recognized significance of cherry leaf roll virus in many perennial plants around the world is increasing dramatically and it is now associated with the decline of many agricultural and forest plants. A unique feature of cherry leaf roll virus is the association of distinct strains with each host species. To further understand this relationship, we determined the complete sequence of the sweet cherry leaf roll virus isolate found in North America. This is the first complete genome of a cherry isolate and of an isolate from North America. This contributes to the dialogue about the host specificity of these virus isolates and will inform development of hypotheses regarding modes and sources of transmission. Field experiments demonstrated that cherry rootstocks offer varying degrees of resistance or tolerance to cherry leaf roll virus. Little cherry disease is re-surging in the Pacific Northwest. Analysis determined that Little cherry virus 2 is the virus largely responsible for the increased incidence of this disease. American hop latent virus is one of three members of the Carlavirus genus that are known to infect hops. However, this virus is unique in that its distribution is restricted to North America. Moreover, previous data indicates that it is serologically distinct from the other carlaviruses that infect hop plants. We determined the completed genomic sequence of this virus for the first time. These data support the very distant relationship that it has to the other viruses of hop. The operation of foundation programs for the development of virus-tested source material for propagation of perennial, vegetatively propagated plants continues to be an effective strategy to help maintain the sustainability of these specialty crops. Thousands of propagation units are distributed each year from this program for hops, temperate climate fruit trees and grapevines. PARTICIPANTS: Kenneth C. Eastwell, WSU-Prosser. TARGET AUDIENCES: Temperate Climate Fruit and Nut tree producers, hop producers, wine and juice grape producers, and other perennial specialty crops PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The identification of rootstocks that offer different responses to cherry leaf roll virus provides growers with options for disease management. Rootstocks that develop a hypersensitive reaction prevent the virus from being transmitted by root grafting. Similarly, a hypersensitive reaction leads to the quick decline of the scion once it becomes infected, and therefore limits its opportunity to be a source of inoculum for further aerial transmission. The rootstocks that offer varying degrees of tolerance and resistance to cherry leaf roll virus were derived from hybrid crosses of related cherry species. Therefore, these species may provide sources of resistance genes that could be incorporated into sweet cherry breeding programs for the development of resistant fruiting cultivars. Many growers are responding to the increased threat from little cherry disease by aggressive tree removal and replacement. Identification of this pathogen led to renewed research in disease management strategies including vector identification and control. Availability of the complete genomic information of American hop latent virus will enable studies to define the origins of this virus to explain its unusual global distribution. Most carlaviruses do not induce visible symptoms so a native host plant of this virus may exist in the environment but is not recognized. By providing a continuing migration of virus-free plants into new plantings and into orchard renovations, the incidence of virus diseases are reduced. Despite current concerns about specific disease situations, the overall phytosanitary status of the related industries is far superior to that of several decades ago. This results in reduced production costs and greater competitiveness of growers in the global market place.
Publications
- No publications reported this period
|
Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: A virus associated with decline of sweet cherry trees was identified as cherry leaf roll virus by serological, host range and molecular analyses. Partial sequence analysis demonstrated a close relationship to the birch and cherry isolates of cherry leaf roll virus from Europe. Similar analyses revealed the presence of cherry leaf roll virus in wild potato from Peru used for potato germplasm development. The biological response of cherry rootstocks to cherry leaf roll virus is highly variable. Fruiting varieties growing on P. avium or P. mahaleb rootstocks become fully infected with cherry leaf roll virus and are sources of secondary spread in the orchard and nursery. However, grafting experiments show that several rootstocks under development that have other Prunus species in their parentage develop a hypersensitive reaction to infection by cherry leaf roll virus. Sowbane mosaic virus can be a contaminant of seed of Chenopodiaceae and spinach (Spinacia oleracea). In this study, the complete genome of a sowbane mosaic virus isolate was characterized and rapid testing strategies were developed to aid in the detection of the virus. PARTICIPANTS: Most activities of this project were performed by project researchers. However, on-farm demonstration plots utilized grower participation under the general direction of the investigator. Commodity commissions, grower groups and other researchers provide input in establishing research direction and needs. TARGET AUDIENCES: Growers and nursery operators are the primary direct benefactors from these research and program development efforts. Information developed in this program is utilized by Federal and State quarantine and certification programs that allow growers and producers access to a greater selection of cultivars. Ultimately, U.S. consumers benefit from reduced production costs, and better access to diverse domestically produced agricultural products. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Cherry leaf roll virus can be seed and pollen borne in some natural and experimental systems; its presence in cherry orchards raises concern about its potential for long term impact on sweet cherry production. The use of rootstocks that are hypersensitive to cherry leaf roll virus can be a valuable tool to minimize secondary spread of the virus in either nursery or fruit production systems. Since cherry leaf roll virus is seed transmitted in P. avium and S. acaule, this virus could be a threat to cherry and potato breeding programs and appropriate vigilance is required. Sowbane mosaic virus is a pollen- and seed-borne virus that infects several of the Chenopodium species commonly used as indicator plants for the study and diagnosis of virus diseases. Contamination of seed in testing programs can lead to spurious conclusions based on herbaceous host range test results. Molecular and serological assays developed for sowbane mosaic virus will assist programs in quickly identifying this contaminant in their programs.
Publications
- Crosslin, J.M., K.C.Eastwell, C.M.Davitt, and J.A.Abad. 2010. First Report of Seedborne Cherry leaf roll virus in Wild Potato, Solanum acaule, from South America. Plant Disease. 94:782-783.
- Eastwell, K.C., and W.E.Howell. 2010. Characterization of Cherry leafroll virus in sweet cherry in Washington State. Plant Disease. 94:1067.
- Eastwell, K.C., D.E.Villamor, C.L.McKinney, and K.L.Druffel. 2010. Characterization of an isolate of Sowbane mosaic virus. Archives of Virology. 155:2065-2067.
|
|