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United States Department of Agriculture

Agricultural Research Service

2011 Annual Report

1a.Objectives (from AD-416)
The long term objectives of this project are to identify causal agents, develop diagnostic assays, identify virus vectors and develop management strategies for controlling virus diseases of small fruit crops. Control strategies will range from improving certification programs with better diagnostics, managing vectors and virus sources, and working with breeders to identify resistant germplasm and cultivars as well as developing resistance using pathogen derived approaches. The priority of diseases to be addressed is determined by their economic impact for growers or processors of these fruits.

1b.Approach (from AD-416)
DsRNA analysis will be used to: 1. Look for viruses in new diseases of small fruit crops as a way to initially determine if a virus(es) is present in symptomatic plants; 2. Re-examine known diseases to look for the presence of additional viruses that may have been overlooked using bioassays and electron microscopy; and 3. Determine if mixed infections are responsible for symptom variation in a single cultivar in different growing areas. Native plants and agricultural crops can serve as important inoculum for viruses studied in this project. Native vegetation and weeds in and adjacent to fields with virus infections will be tested for the presence of the viruses being studied using the tests developed in subobjective 1a and those already available. We will use standard molecular biology techniques to develop full length clones of the three RNAs of RBDV and test them for infectivity after generating RNA in various transcription systems.

3.Progress Report
This is the final report for the project 5358-22000-033-00D that will be terminated in September of 2011. This project is being rolled into 5358-21000-037-00D, entitled, "Physiology and Genetic Improvement of Small Crops". The research will be continued but in NP301 rather than NP303.

Substantial results were realized over the 4 years of the project. The Pacific Northwest region of the United States is a leading producer and exporter of berry crops, grapes and wine. Combined, these crops are subject to more than 100 different viruses that occur worldwide. Many of these viruses cause economic damage in single infections or mixed virus infections, resulting in constraints for production and export. Over the course of the project, we have significantly improved our understanding of the importance of virus complexes in causing diseases in these crops. We have shifted the paradigm from disease is caused by a pathogen to virus diseases of woody perennials are often caused by virus complexes. In the study of these virus complexes, we have characterized new viruses that infect, blackberry (14), blueberry (3), raspberry (4) and strawberry (4). Diagnostic assays have been developed for these 25 viruses and are being used in quarantine and certification programs as well as in epidemiological research. An outcome of the research on strawberry virus complexes and the epidemiology of the viruses has led to modification in control measures that resulted in the use of fewer pesticides and effective control of a virus complex that was causing at least $25 million in losses per year. In raspberry, the work has led to an understanding of the importance of virus complexes in causing crumbly fruit. This work has opened the possibility of alternative control measures for control of this disease since we now know that some of the viruses are vectored by aphids, where previously it was thought that the causal virus was pollen transmitted. Since this is the only laboratory that focuses on viruses in berry crops, we are involved with research throughout the United States. For example, identification of new viruses in blackberry and blueberry in the southeastern U.S. and MI was done in collaboration with colleagues in those regions. The virus characterization is usually done in our laboratory and transmission studies in the region where the disease occurs. The emphasis on virus complexes is to identify the critical viruses necessary to cause disease and their vectors. In developing management strategies, efforts are targeted toward controlling one of these critical viruses, which controls the disease even though all the viruses are not controlled. Additionally, we have worked with plant breeders in the United States to “clean up” new small fruit cultivars of viruses before they are released to the industry; this has led to improved quality of the plant material that is available to growers. The overall impact of these accomplishments is that producers have new information on pest management decisions, better quality planting stocks, and more effective and environmentally friendly management tools to control virus diseases of the berry crops.

1. Raspberry crumbly fruit viruses sorted out. Virus induced crumbly fruit in raspberry is the reason that growers in the Pacific Northwest need to replant every 5-6 years. ARS research in Corvallis, Oregon has characterized the viruses involved in this disease and their vectors as well as the virus/vector interactions. Based on sequence information, Raspberry latent virus was expected to be transmitted by leafhoppers, but in greenhouse tests was found to be transmitted by aphids. This is an example of why it is necessary to confirm the best guess of the vector based on sequence information with transmission experiments. If unmanaged, this disease complex costs growers from 1000 - 3000 dollars per acre per year; therefore, providing information on the virus vector and its biology will be a great benefit to growers by helping them reduce the impact of this disease and be more competitive in national and international markets.

2. High throughput sequencing for virus characterization. This research was undertaken to determine the utility of high throughput sequencing for the identification of new viruses associated with plant diseases in perennial crops. Plants exhibiting virus-like symptoms were used for these studies, and in the initial phase several types of hosts were tested including: Blueberry, Blackberry, Fig, Raspberry, Redbud, Rose, Strawberry and Sugarberry. We identified new viruses in each of the hosts examined, and several of these viruses have been characterized. This technology is proving especially useful and cost effective in characterizing virus complexes multiple viruses can be characterized simultaneously. With some refinement, this will be a very useful technology for plant quarantine to determine the virus (and other pathogens) status of material in an efficient manner, and reduce the risk of introducing exotic plant pathogens into the United States.

Review Publications
Fuchs, M., Abawi, G.S., Marsella-Herrrick, P., Cox, R., Cox, K.D., Carrol, J.E., Martin, R.R. 2010. Tomato ringspot virus and tobacco ringspot virus in highbush blueberry in New York State. Journal of Plant Pathology. 92:451-459.

Martin, R.R., Zhou, J., Tzanetakis, I.E. 2011. Blueberry latent virus: An amalgam of the Totiviridae and Partitiviridae. Virus Research. 155:175-180..

Kraus, J., Cleveland, S., Tzanetakis, I.E., Keller, K.E., Putnam, M., Martin, R.R. 2010. A new Potyvirus sp. infects Verbena exhibiting leaf mottling symptoms. Plant Disease. 94:1132-1136.

Quito, D.F., Jelkmann, W., Tzanetakis, I.E., Keller, K.E., Martin, R.R. 2011. Complete sequence and genetic characterization of Raspberry latent virus, a novel member of the family Reoviridae. Virus Research. 155:397-405..

Hadidi, A.F., Olmos, A., Pasquini, G., Barba, M., Martin, R.R., Shamloul, A. 2011. Double-stranded RNAs and their use for characterization of recalcitrant viruses. In: Hadidi, A., Barba, M., Candresse, T., and Jelkmann, W., editors. Virus and Viruslike Diseases of Pome and Stone Fruit. St. Paul, MN, APS Press. 323-326.

Hadidi, A.F., Olmos, A., Pasquini, G., Barba, M., Martin, R.R., Shamloul, A. 2011. Polymerase chain reaction for detection of systemic plant pathogens. In: Hadidi, A., Barba, M., Candresse, T., and Jelkmann, W., editors. Virus and Viruslike Diseases of Pome and Stone Fruit. St. Paul, MN, APS Press. 341-359.

Last Modified: 5/28/2015
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