Progress 07/01/07 to 06/30/10
Outputs
OUTPUTS: Grapevine leafroll disease (GLRD) is a significant constraint to sustainability of the grape and wine industry in WA. Basic and applied research aspects of GLRD were studied in a holistic manner. Study results indicate viruses associated with GLRD can be present systemically in different parts of infected grapevines. Information is used to develop robust sampling strategies for virus detection, benefiting growers and certified nurseries in understanding the epidemiology of GLRD and its impact on vine health and fruit quality. Among 12 grapevine viruses documented to date, Grapevine leafroll-associated virus-3 (GLRaV-3) was the most prevalent and economically important. Studies on Grapevine fanleaf virus (GFLV) indicated random distribution of virus-infected grapevines in Pinot Noir, Merlot, Cabernet Franc and Chardonnay blocks, suggesting that virus dissemination was through planting materials. Since there is no credible evidence of the presence of the dagger nematode vector (Xiphinema index) in WA vineyards, rouging of infected vines and replanting with virus-tested cuttings would be an effective strategy to eradicate GFLV from virus-infested vineyard blocks. Planting new vineyards with virus-tested planting materials is vital to block further dissemination of GFLV. Our results indicate that genetically distinct isolates of GFLV, GLRaV-2 and Grapevine rupestris stem pitting-associated virus (GRSPaV) exist in different vineyard blocks as a consequence of introduction and subsequent dissemination of infected grapevine cuttings. Outputs of this research have enabled development of more robust molecular typing assays as a practical and reliable means of detection and discrimination of virus isolates that might escape ELISA-based detection in 'Clean' plant programs. Such molecular approaches are critical for viruses where no reliable antibodies are available for detection by ELISA. We have documented 2 additional grapevine viruses that were not known previously in WA vineyards, stressing the need for continued vigilance to ensure high standards of plant hygiene. Our results suggest that differences in photosynthetic gas exchange and chlorophyll fluorescence between virus-infected and healthy vines were not apparent before veraison, but were significantly higher after veraison. Studies on the effect of GLRD on wine grape production under WA conditions shows significant negative impacts on the performance of own-rooted Merlot grapevines and on grape yield and fruit quality. Results clearly indicate negative impacts on fruit maturity indices throughout berry development. Results from wine made from this fruit, although preliminary, showed for the first time that virus infection can alter wine characteristics both positively and negatively. Studies on spatial distribution of grapevines with GLD symptoms in a new Cabernet Sauvignon block planted in close proximity to an old Cabernet Sauvignon block heavily infested with GLRD indicated the potential risk of disease spread to young, virus-free plantings from neighboring vineyards heavily infested with the disease. PARTICIPANTS: Project Leader, Naidu Rayapati, Ph.D. and doctoral students (Olufemi Alabi and Sridhar Jarugula) and post-doctoral research associates (Tefera Mekuria and Linga R. Gutha) have made scientific and material contributions to the project. Several growers and viticulturists provided access to vineyards for collecting samples and conducting field experiments. TARGET AUDIENCES: Wine grape growers and industry stakeholders, certified nurseries, scientific community and regulatory agencies in Washington State. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
In summary, a combination of lab- and field-based research conducted during this period generated new knowledge for an improved understanding of various aspects of the biology and epidemiology of GLRD and other grapevine viruses. Continued research efforts will help to develop science-based strategies for mitigating negative impacts of viruses in WA vineyards. The project has generated science-based knowledge on economically important virus diseases of wine grapes. Project results, together with previous reports from WA and OR vineyards, indicate the wide distribution of GLRaV-3 in several grapevine cultivars in the Pacific Northwest region. Cumulative results accrued during the past 5 seasons provided a comprehensive picture of different grapevine viruses present in WA vineyards.This knowledge is helping Clean Plant programs and Certified Nurseries in supplying virus-tested planting materials to promote sustainability of the wine grape industry in the PNW region. The other potential benefits of this project include planting suitable wine grape cultivars with reduced usage of pesticides to control mealy bugs that spread grapevine leafroll disease. This could lead to production of quality grapes for making premium wine with desirable health benefits and a reduction in environmental pollution and human health risks. Various extension and outreach efforts have helped to increase awareness of the negative impact of virus diseases among researchers, extension educators, growers, consultants and industry stakeholders to foster sustainability of wine grape industry and increase the national (and global) market share for grape growers in the state.
Publications
- No publications reported this period
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Six different grapevine leafroll-associated viruses (GLRaVs), namely GLRaV-1, -2, -3, -4, -5 and -9, Grapevine Virus A, Grapevine Virus B and Grapevine rupestris stem pitting-associated virus (GRSPaV), Grapevine fanleaf virus (GFLV), Grapevine fleck virus and Grapevine syrah virus-1 were documented in Washington vineyards. GLRaV-3 was found to be the most widespread in different wine grape cultivars. Mixed infections of these viruses in different combinations were also found in some wine grape cultivars. GFLV was found occurring as mixed infection with other grapevine viruses in cvs. Pinot Noir, Chardonnay, and Cabernet Franc, and as single infection in cv. Merlot. Variability of fanleaf disease symptoms in different cultivars was also observed. The absence of the nematode vector (Xiphinema index) and the random distribution of GFLV-infected grapevines in Pinot Noir and Chardonnay blocks suggests primary spread through planting virus-infected cuttings rather than infield transmission by the nematode vector. Studies on genetic diversity of GFLV isolates revealed interspecies recombination in RNA2 involving sequences from other nepoviruses (viz. Grapevine deformation virus and Arabis mosaic virus). Studies were conducted on molecular diversity of GRSPaV isolates collected from different wine grape cultivars grown in the Pacific Northwest. Molecular diversity in the coat protein (CP) and a portion of helicase-encoding region (HR) of the RNA-dependent RNA polymerase was assessed relative to virus isolates from other grape-growing regions. Using a phylogenomic approach and population genetics parameters, the highly variable nature of GRSPaV was established. The discordant gene phylogenies obtained for some CP and HR sequences and the identification of potential recombination events involving parents from different lineages provided strong evolutionary evidence for genetic diversity among GRSPaV isolates. Studies were initiated to measure the impact of GLRaV-3 on own-rooted grapevines of cv. Merlot in cool-season viticulture. The results have shown significant negative impacts of GLRaV-3 on photosynthesis, chlorophyll fluorescence, fruit yield and berry quality attributes. Epidemiological studies showed spread of GLD from heavily infected older blocks to neighboring healthy plantings and subsequent secondary spread within healthy vineyard blocks. A strain of Tobacco streak virus causing symptomless infection was identified in Coreopsis auriculata 'Nana'. Partial molecular analysis of a virus in Crocosmia spp. indicated the presence of a strain of Bean yellow mosaic virus. Molecular characterization of two new 'legumoviruses' (genus Begomovirus; family Geminiviridae) naturally infecting soybean in Nigeria was completed. Banana bunchy top virus was reported for the first time from Cameroon. Using molecular biological approaches, the presence of Bean common mosaic virus and Cucumber mosaic virus was confirmed in diseased yardlong bean plants in Indonesia. Tomato spotted wilt virus and Peanut bud necrosis viruses were observed for the first time in tomato in Indonesia. PARTICIPANTS: Several scientists from collaborating institutions in the US (Robert R. Martin at USDA-ARS, Corvallis and Alexander Karasev at the University of Idaho) and developing countries (P. Lava Kumar at the International Institute of Tropical Agriculture, Nigeria, G. Karthikeyan at Tamil Nadu Agricultural University, India and Tri Damayanti at Bogor Agricultural University, Indonesia) have made scientific and material contributions to the project. Doctoral students (Olufemi Alabi and Sridhar Jarugula) and post-doctoral research associates (Tefera Mekuria and Linga R. Gutha) in Rayapati's lab have contributed to the advancement of project activities. Several growers and viticulturists have provided access to vineyards for collecting samples and conducting field experiments. TARGET AUDIENCES: Wine grape growers and industry stakeholders, certified nurseries, ornamental nursery industry, the scientific community and regulatory agencies, and scientists and farmers in developing countries. PROJECT MODIFICATIONS: The revised CRIS proposal expanded its scope to include on-going research projects on grapevine virus diseases and viruses impacting horticultural crops (viz. vegetables, small fruits and ornamentals) in Washington State. In addition, activities include addressing virus diseases of economic significance to subsistence agriculture for enhanced food security in developing countries of Africa and Asia.
Impacts
The project has generated science-based knowledge on economically important virus diseases of wine grapes. The project results, together with previous reports from Washington and Oregon State vineyards, indicate the wide distribution of GLRaV-3 in several grapevine cultivars in the Pacific Northwest region. This knowledge is helping Clean Plant programs and certified nurseries to supply virus-tested planting materials to promote sustainability of the wine grape industry in the Pacific Northwest region. The other potential benefits of this project include planting suitable wine grape cultivars with reduced usage of pesticides to control mealybugs that spread grapevine leafroll disease. This could lead to production of quality grapes for making premium wine with desirable health benefits and a reduction in environmental pollution and human health risks. Various extension and outreach efforts have helped to increase awareness of the negative impact of virus diseases among researchers, extension educators, growers, consultants and industry stakeholders to foster sustainability of wine grape industry and increase the national (and global) market share for grape growers in the state. The project outputs also brought increased awareness of new virus diseases infecting perennial ornamentals in Washington State. Research conducted on virus diseases in soybean, banana, tomato and yardlong bean will contribute to reducing yield losses to crops grown by poor farmers, thereby increasing food security in developing countries. The project increased the level of engagement of university faculty in addressing global dimensions of agriculture and provided a valuable learning experience that can be incorporated into undergraduate teaching and graduate research programs at Washington State University.
Publications
- Rayapati, N.A., E.M.Perry, F.Pierce, and T.Mekuria. 2009. The potential of spectral reflectance technique for the detection of Grapevine leafroll-associated virus-3 in two red-berried wine grape cultivars. Computers and Electronics in Agriculture. 66:38-45.
- Mekuria, T., L.R.Gutha, R.R.Martin, and N.A.Rayapati. 2009. Genome diversity and intra- and interspecies recombination events in Grapevine fanleaf virus. Phytopathology. 99(12):1394-1402.
- Karasev, A.V., and N.A.Rayapati. 2009. First report of Grapevine leafroll-associated virus-3 in six wine grape cultivars in Idaho. Plant Disease. 93:1218.
- Oben, T.T., R.Hanna, J.Ngeve, O.J.Alabi, N.A.Rayapati, and P.Lavakumar. 2009. Occurrence of banana bunchy top disease caused by the Banana bunchy top virus on banana and plantain (Musa sp.) in Cameroon. Plant Disease. 93:1076.
- Damayanthi, T.A., and N.A.Rayapati. 2009. Identification of Peanut bud necrosis virus and Tomato spotted wilt virus in Indonesia for the first time. Plant Pathology. 58:782.
- Rayapati, N.A., T.Mekuria, O.J.Alabi, S.Jarugula, G.Karthikeyan, L.R.Gutha, and R.R.Martin. 2009. Current status of grapevine viruses in the Pacific Northwest vineyards of the United States. 16th Meeting of the International Council for the study of virus and virus-like diseases of the grapevine. Ed. Elisabeth Boudon-Padieu. International Council for the study of virus and virus-like diseases of the grapevine. 8-31-09 to 9-4-09. Dijon, France. Le Progres Agricole et Viticole-ISSN 0369-8173. Pages 108-109.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Studies documenting the occurrence of viruses in different wine grape cultivars during the 2008 growing season were continued. Similar to previous seasons, Grapevine leafroll-associated virus (GLRaV)-1, -2, -3, -4, -5, and -9, Grapevine Virus A, Grapevine Virus B, Grapevine rupestris stem pitting-associated virus (GRSPaV) were detected in several cultivars. In addition, Grapevine fanleaf virus (GFLV) was detected for the first time in three red- and one white-berried wine grape cultivars. These viruses were found occurring as either single or mixed infections in individual grapevines. GLRaV-3 was found to be the most prevalent among the viruses documented. The genetic diversity of GLRaV-1, GLRaV-2, GRSPaV, GFLV in Washington State vineyards was assessed by analyzing the nucleotide sequences of specific genomic fragments amplified from different isolates of each virus. The results have shown molecular variability among these viruses, indicating the presence of distinct strains in the vineyards. Spatial distribution of infected grapevines was mapped in two wine grape cultivars to understand the epidemiology of grapevine leafroll disease (GLD). The results indicated clustering of symptomatic vines across a given row in both cultivars. These results are consistent with data collected from previous years in other cultivars from geographically widely separated vineyards. The spread of GLD to new plantings from a neighboring older block heavily infected with GLD was monitored. The results, based on visual symptoms and testing of symptomatic vines, indicated a high percentage of symptomatic vines in the young block. This suggests GLD spread into a newly planted block from a heavily infected neighboring block. Greenhouse studies have indicated root grafting as a possible means of virus spread between neighboring vines. The potential of leaf spectral reflectance changes between GLRaV-3 infected and uninfected grapevines of two grape cultivars. PARTICIPANTS: N. Rayapati, Project Leader. R. R. Martin from USDA-ARS, Corvallis, OR, has made scientific and material contributions to the project. Doctoral students (Mr. Olufemi Alabi and Mr. Sridhar Jarugula) and post-doctoral research associates (T. Mekuria, G. Karthikeyan, and L.R. Gutha) have contributed to the advancement of knowledge on grapevine virus diseases presented in this report. Several growers and viticulturists have provided access to vineyards for sample collections and conducting field experiments. TARGET AUDIENCES: Wine grape industry stakeholders, certified nurseries, scientific community and regulatory agencies. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The strategic knowledge on viruses has been disseminated widely through scientific and industry-sponsored meetings, tail-gate meetings, workshops, an extension bulletin (Grapevine leafroll disease EB 2027E), pod casts, DVD, scientific publications and Web site (http://wine.wsu.edu/virology/) to different stakeholders for increased awareness of grapevine virus diseases. The outputs of the project have increased knowledge of grapevine viruses and the epidemiology of grapevine leafroll disease. The web site, extension publications and workshops promoted awareness of virus diseases among wine grape industry stakeholders and regulatory agencies. Industry-researcher partnerships have been established to address virus diseases in order to make the wine grape industry more sustainable.
Publications
- Jarugula, S., M.J. Soule, A. Rowhani, and N.A. Rayapati. 2008. First report of Grapevine leafroll-associated virus-9 in Washington State vineyards. Plant Disease 92:485.
- Mekuria, T., R.R. Martin, and N.A. Rayapati. 2008. First report of the occurrence of Grapevine fanleaf virus in Washington State vineyards. Plant Disease 92:1250.
- Karthikeyan, G., O.J. Alabi, T. Mekuria, R.R. Martin, and N.A. Rayapati. 2008. Occurrence of two distinct molecular variants of Grapevine leafroll-associated virus-1 in the Pacific Northwest vineyards. Proc. of the 2nd Annual National Viticulture Research Conference. July 9-11, University of California, Davis.
- Mekuria, T., R.R. Martin, and N.A. Rayapati. 2008. First report of the occurrence of Grapevine fanleaf virus in the Washington State vineyards. Proc. of the 2nd Annual National Viticulture Research Conference. July 9-11, University of California, Davis.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Grapevine leafroll disease (GLD) is the most important viral disease affecting wine grapes in Washington State. This project was developed to investigate various aspects of the biology and epidemiology of GLD and hence develop strategies for reducing the losses associated with the disease. Reconnaissance studies were conducted to document the occurrence of grapevine viruses in Washington vineyards. Using molecular diagnostic techniques, Grapevine leafroll-associated virus (GLRaV)-1, -2, -3, -4, -5, and -9, Grapevine Virus A, Grapevine Virus B, and Grapevine rupestris stem pitting-associated virus (GRSPaV) have been detected in several red- and white-berried wine grape cultivars. These viruses have been shown to occur as single or mixed infections in individual grapevines. GLRaV-3 was found to be the most prevalent among the viruses documented. Molecular studies have confirmed for the first time the occurrence of the Red Globe strain of GLRaV-2 in two red-berried wine grape
cultivars and GLRaV-9 in five red-berried wine grape cultivars. Studies on the timing of sampling for virus detection have shown that GLRaV-3 can be reliably detected any time during the growing season by RT-PCR and ELISA in petiole samples collected from four wine grape cultivars. However, RT-PCR revealed certain advantages over ELISA for reliable and consistent detection of the virus throughout the season. A multiplex RT-PCR assay has been validated for the detection of GLRaV-3 and GRSPaV in field samples using a housekeeping gene of plant origin as an internal control. The spatial pattern of GLD distribution was monitored for the past three seasons in two red-berried wine grape cultivars in geographically widely separated vineyards. The results showed clustering of GLD-infected grapevines along individual rows, suggesting that GLD spreads between neighboring grapevines within rows. The pattern of spatial distribution suggested that the mode of GLD spread could be similar in
different wine grape cultivars. Potted experiments conducted under greenhouse conditions suggested that within-field movement of grape mealybugs (Pseudococcus maritimus) is probably extremely slow, and that, unless this insect is dispersed by other means, it is unlikely to be totally responsible for rapid spread of grapevine leafroll disease. Vector transmission studies have indicated that Western grape leafhopper (Erythroneura elegantula Osborn) and Virginia creeper leafhopper (Erythroneura ziczac Walsh) are not capable of transmitting GLRaV-3.
PARTICIPANTS: This is a multi-disciplinary project addressing various aspects of virus diseases in wine grapes in a holistic manner. K. Eastwell (Virology) and D. James (Entomology) from Washington State University, R. Martin (Virology) from USDA-ARS, Corvallis, OR, Dr. A. Rowhani (Virology), University of California, Davis, CA, have made contributions to the project. Two doctoral students (Mr. Olufemi Alabi and Mr. Sridhar Jarugula) and three post-doctoral research associates (T. Mekuria, G. Karthikeyan, T. Grasswitz) have contributed to the advancement of knowledge on grapevine virus diseases. Several growers and viticulturists have provided access to vineyards for sample collections and conducting field experiments.
TARGET AUDIENCES: The intended target audience is wine grape industry stakeholders, certified nurseries, scientific community and regulatory agencies. The strategic knowledge on viruses and insect vectors generated during this project period has been disseminated widely through industry-sponsored meetings, tail-gate meetings, workshops, newsletters, scientific publications and a Web site (http://winegrapes.wsu.edu/virology/) to different stakeholders for increased awareness of grapevine leafroll disease and other viruses.
PROJECT MODIFICATIONS: A revised project will be submitted in 2008
Impacts
Research outputs have provided science-based knowledge for an improved understanding of the epidemiology of grapevine leafroll disease. The prevalence of different viruses as single and mixed infections in individual grapevines highlights the importance of testing for different viruses in virus indexing programs. Improved sampling strategies and concurrent detection of multiple viruses in a given sample will assist in reliable diagnosis of viruses in a cost-efficient manner. An analysis of the spatial distribution of GLD will help to study various means of spread of the disease and develop appropriate control strategies to minimize the negative impact of the disease.
Publications
- No publications reported this period
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