Source: CORNELL UNIVERSITY submitted to NRP
US-UK COLLABORATIVE: SPATIAL EPIDEMIOLOGY OF A VECTOR-BORNE POTATO VIRUS: INTERACTIONS BETWEEN LANDSCAPE, HOSTS AND VECTORS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1004884
Grant No.
2013-67013-21235
Cumulative Award Amt.
$1,640,000.00
Proposal No.
2013-04567
Multistate No.
(N/A)
Project Start Date
Sep 1, 2013
Project End Date
Aug 31, 2018
Grant Year
2013
Program Code
[A1222]- Ecology and Evolution of Infectious Diseases
Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
Section of Ecology and Systematics
Non Technical Summary
Potato virus Y (PVY) is one of the most serious pathogens of potato crops worldwide, reducing both yield and quality. New recombinant strains of PVY have emerged in recent decades, adapted rapidly to the potato ecosystem, and dominated virus populations over vast geographical areas, including both the United States and the United Kingdom. The overall objective of this proposal from the US-UK partnership is to understand the ecological factors that allow recombinant strains of PVY to emerge, spread rapidly, and become the dominant viruses.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2121310107040%
2121310110120%
2121310113020%
2121310208020%
Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1310 - Potato;

Field Of Science
1101 - Virology; 1130 - Entomology and acarology; 1070 - Ecology; 2080 - Mathematics and computer sciences;
Goals / Objectives
The overarching goal of this proposal is to identify ecological factors that allow new emerging viruses to predominate in host communities. To do this, we have assembled a team of ecologists, plant pathologists, plant physiologists, entomologists, and mathematical modelers from the United States (funded by USDA) and the United Kingdom (funded by BBSRC). We will collaborate to evaluate the influence of landscape structure, vector community composition, transmission dynamics, within-host processes, and virus recombination on the emergence and spread of new vector-borne viruses, using the economically important aphid-transmitted Potato virus Y (PVY) as a model system. PVY is one of the most serious pathogens of cultivated solanaceous crops worldwide, reducing both yield and quality. New recombinant strains of PVY have emerged in recent decades, adapted rapidly to the potato ecosystem, and dominated virus populations over vast geographical areas, including both the United States and the United Kingdom. The recombinant strains must have a fitness advantage to emerge rapidly as the dominant virus population, but the ecological factors influencing fitness are not clearly understood and represent an overall objective of this proposal. 1) Determine whether landscape structure influences the composition of the vector community, patterns of PVY transmission, and prevalence of emerging disease [USDA]. Agroecosystems are embedded in landscapes composed of a variety of ecosystems, including natural habitats, but agricultural landscapes vary in their composition and complexity. As compared to uniform landscapes, complex landscapes offer a diversity of host plants that may favor some vector species while limiting others, thus changing the species composition of the vector community, altering the spatial and temporal structure of virus communities, and modifying disease dynamics. 2) Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [USDA]. We will focus on the differential transmission of pathogens by different vector species. Although most plant viruses are transmitted by more than one vector species, mathematical theory addressing multiple vectors is rare. The spatial dynamics of vector colonization and virus transmission are key to predicting rates of virus spread and the likelihood of coinfection that may lead to recombination. These dynamics are particularly complex in virus systems like PVY, where the virus is transmitted by many aphid species. 3) Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [BBSRC]. Both genetic variation among host plants and ontogenetic and physiological changes within hosts leading to mature plant resistance (MPR) can alter the probability of successful transmission and infection. Large differences in MPR between cultivars and virus strains have been demonstrated, but the mechanisms causing these changes are not well understood.
Project Methods
We will evaluate the ecological factors that may lead to virus recombination and emergence using field surveys, experimental sentinel plants, manipulative field experiments, lab experiments and mathematical models to explore PVY dynamics at three scales: the landscape scale, within-field scale, and within-host scale. Objective 1: We expect increased aphid species diversity in heterogeneous landscape, leading to a decrease in the average transmission efficiency of vectors and reduced spread of PVY. We will address this hypothesis in two contrasting regions of potato production: the heterogeneous landscapes of upstate New York, and the simplified agricultural landscapes of large-scale monocultures in central Wisconsin. Vector abundance and diversity will be measured throughout the season using water traps. Plants will be sampled weekly for PVY using ELISA and RT-PCR. For the Wisconsin landscapes, we will compare field-level data on aphid community composition and abundance in varying landscapes with an estimate of the regional species pool based on suction traps. We will use a spatially explicit, agent-based modeling platform to ask how landscape composition influences vector abundance, and how vector community composition and landscape structure interact to shape virus dynamics on agricultural landscapes of varying spatial heterogeneity. Objective 2: We will use field and laboratory experiments to address the role of vector community composition on virus emergence. First, manipulative field experiments will be used to determine the effects of the vector community on virus spread and rates of coinfection. Second, a series of lab experiments will explore: 1) the spatial and temporal dynamics of single and mixed strain infections in the plant; 2) how these dynamics influence vertical and horizontal transmission of virus populations; and 3) how genetic heterogeneity of vector populations influence the transmission efficiency and genetic diversity of virus populations. Mathematical modeling will integrate information from empirical and field studies to address how vector community composition and dispersal affect rates of disease transmission and coinfection. Objective 3: Our hypothesis is that MPR is a result of the sink/source status of the inoculated tissue and phloem connectivity between it and tubers. We will investigate phloem entry and connectivity using fluorescent dyes, radiolabelled carbon, and GFP-tagged virus in genotypes of potato that differ in virus susceptibility and maturity. The results will be used to develop markers of resistance or susceptibility that can be used in field assays to provide data for predictive models being developed in the other objectives within this proposal. We will use a spatially specific within-host model to help determine whether MPR resistance is due to a physical or biochemical mechanism.

Progress 09/01/13 to 08/31/18

Outputs
Target Audience:Target audiences for this work include scientists and researchers in plant pathology, entomology, and ecology. In addition, potato growers, especially seed producers, are an important target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided training to seven postdoctoral scientists (2 at Cornell, 1 at the University of Wisconsin, 4 at the University of St. Andrews), one Wisconsin associate researcher, one Cornell Research Support Specialist, six graduate students (3 plant pathologists, 1 entomologist, 2 ecologists), and nine undergraduate students. At Cornell University, postdocs learned methods related to vector biology, virology and confocal microscopy. Eight Cornell undergraduate students and five graduate students have worked in the Gray and Power labs to learn various techniques in virology, molecular biology, vector biology and statistics. In addition, one Cornell undergraduate in mathematics has worked with Co-PI Jones to learn approaches for modeling the dynamics of insect-transmitted plant pathogens. Cornell Research Support Specialist Peters was trained in multiplex rtPCR training and protocol development at the Evolutionary Genetics Core facility (EEB, Cornell University). Peters and two graduate students also undertook ArcGIS and QGIS software training and protocol development at Cornell University. At the University of Wisconsin, the project provided training for Associate Researcher Emily Duerr in the Department of Entomology. The Associate Researcher completed a course in multivariate statistics and a short course in structured equation modeling which will better enable the staff scientist to undertake spatial analyses. At the University of St. Andrews and James Hutton Institute, postdocs have been trained in new technical skills (qPCR, microarray analysis using GeneSpring and Mapman), presentation skills, and scientific writing skills. One undergraduate and one graduate student have been trained in plant virology and host resistance mechanisms. How have the results been disseminated to communities of interest?Presentations at Scientific Meetings Alyokhin, A., Beg, S., Benedict, C., Dill, J., Dwyer, J., Frost, K., Groves, R., Lagos-Kutz. D., Rondon, S. and Wenninger, E. Multistate effort to understand aphid diversity and PVY spread in potatoes in the United States. Entomological Society of America, Annual Meeting. Poster presentation (D3529), Denver, CO, November 2017. Da Silva, W.L. and Gray, S.M. 2015. Changes in the population structure of PVY during systemic movement in a potato plant Phytopathology 105(Suppl. 4):S4.32 Gray, S.M. 2014. Potato Virus Y (PVY): A rapidly changing problem for the seed and commercial potato industries. Keynote presentation, Annual meeting of the Korean and Japanese Phytopathology Societies, Busan, South Korea, October 2104. Gray, S.M. 2015. Biological and economic impacts of emerging potato necrotic viruses and the development of comprehensive and sustainable management practices. Invited speaker - Washington State Potato Growers Conference, Richland, WA. January 2015. Gray, S.M. 2015. PVY: A Problem for the US Seed Potato Industry. Invited speaker - Maine Potato conference. Presque Isle, ME. March 2015. Gray, S. 2017. Potato virus Y is seed potato's #1 problem and is an unintended consequence of science, regulators actions and farming practices. Invited seminar at the Dept of Plant Pathology, North Carolina State University, April 2017 Gray, S. 2018. Emerging and evasive tuber necrotic viruses affecting potato health and international trade. Invited seminar at Procinorte Conference, Merida, Mexico August 2018 Gray, S. 2018. Emerging and evasive tuber necrotic viruses affecting potato health and international trade. Invited seminar at Agdia, Inc. Elkhart, IN, September 2018 Gray, S., Charkowski, A., McIntosh, C., and Gudmestad, N. Enhancements to Seed Potato Certification: Adapting to Meet Emerging Challenges and Maintain Profitable Potato Production. Invited seminar at the 2018 Potato Expo, Orlando, FL. January 2018. Groves, R.L. Potato Exposition. Seed Sector Breakout Session. "PVY and Other Emerging Viruses: Best Management Practices to Minimize Virus Levels in Seed Crops". Orlando, FL, January 2015. Groves, R.L., Frost, K.E., Charkowski, A.O., Duerr, E.J., Crockford, A.B. and Huseth, A.S. Wisconsin Seed Potato Industry Association. "Influence of regional landscapes on Potato virus Y incidence in seed potato", Antigo, WI. January 2015. Groves, R.L. Clements, J., Garcia, M. and Frost, K. 2017. BBSRC UK-US Joint Meeting, 'Vector-borne diseases in the UK & US: common threats and shared solutions'. Davis, CA, October 2018. Kumar, P., Cowan. G.H., Roberts, A.G., Tobin, A.K. and Torrance, L. 2015. Studies on Mature Plant Resistance against Potato Virus Y in Solanum tuberosum L. Advances in Plant Virology Conference, Birmingham UK. Kumar, P. 2016. 16th Triennial Meeting of the Virology Section of the European Association of Potato Research, Slovenia. Kumar, P. 2016. Virology Meeting, The James Hutton Institute, Dundee, Scotland. Kumar, P., Cowan. G.H., Roberts, A.G., Tobin, A.K. and Torrance, L. 2017. Recombinant strains of potato virus Y overcome mature plant resistance in Solanum tuberosum. 20th EAPR Triennial Conference - PVYwide, Versailles, France, July 2017. Kumar, P., Cowan. G.H., Roberts, A.G., Tobin, A.K. and Torrance, L Mature plant resistance in potato, its implications in PVY dynamics and management". India-Scotland research symposium, The James Hutton Institute, Dundee, Scotland UK. 2017. Kumar, P., Cowan. G.H., Tobin, A.K., Torrance, L and Roberts, A.G. The Effect of Mature Plant Resistance (MPR) on PVY Infection. Biochemical Society Conference: Taming Plant Viruses - Fundamental Biology to Nanobiotechnology, Pitlochry, Scotland, November 2016. Kumar, P., Cowan. G.H., Tillemans, V., Roberts, A.G., Tobin, A.K. and Torrance, L. Studies on Mature Plant Resistance against Potato Virus Y in Solamun tuberosum. Ecology and Evolution of Infectious Disease Annual Meeting, York, UK, 2018. Mondal, S., S. Gray, M. Ghanim, 2016. Potato virus Y strains co-localize and compete in single epidermal leaf cells. American Phytopathological Society annual meeting, August 2016. Mondal, S. and S. Gray. 2017. Strain specificity of helper components encoded by Potato virus Y. Phytopathology. Abstract from APS annual meeting August 2017. Mondal, S. and Gray, s. 2018. Within-plant distribution of PVY strain mixtures differs spatio-temporally in potato cultivars. International Congress of Plant Pathology, Boston, MA. July 2018 Ruark, S. and Gray, S. 2018. Impact of single-season Potato virus Y epidemics on small mixed-acreage vegetable farms. International Congress of Plant Pathology, Boston, MA. July 2018. Power, A. G. 2016. Symposium on Global Science to Protect our Global Farm, American Association for the Advancement of Science, Washington, DC Power, A. G. 2016. National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN Power, A. G. 2016. VectorBITE Research Symposium, University of South Florida, Tampa, FL Power, A. G. 2016. Wild Plant Pathosystems Meeting, Helsinki, Finland. Power, A. G. 2017. Ecology and Evolution of Infectious Disease Meeting, Santa Barbara, California Power, A. G. 2017. Plant-Microbe Interactions Meeting, National Institute of Food and Agriculture, USDA, Washington, DC Power, A. G. 2018. International Congress of Plant Pathology, Boston, MA Roberts, A.G. 2016. Biochemical Society, Pitlochry, Scotland. Torrence, L. 2016. Advances in Plant Virology, Association of Applied Biologists, Greenwich, UK. Torrence, L. 2016. Advances in Plant Virology meeting, University of Greenwich, UK Torrence, L. 2016. International Plant Virus Epidemiology Symposium, Avignon. France. Torrence, L. 2018. International Congress of Plant Pathology, Boston, USA Vogelaar, M. "The involvement of callose synthase and lipid metabolism in PVY infection." Oral presentation of MSc Thesis, James Hutton Research Institute, October 2018. Vogelaar, M. University of Wageningen, December 2018. Grower and Industry Meetings Gray, S. Emerging potato viruses: Challenges to the seed certification process. Invited talk at the Syngenta Potato Partners Program, November 2016, Torrey Pines, CA ~150 attendees. Gray, S. Potato virus Y management in commercial potatoes. Invited talk at the Michigan Potato Growers Conference, January 2017, Mt Pleasant, MI ~ 300 attendees. Groves, R.L. Evidence for geographic variation in aphid species prevalence and abundance in captures. 44th Annual Hermiston Farm Fair Seminar, Hermiston, OR. November 2017, (N=85). Groves, R.L. Management of Potato virus Y; timing treatments for aphid vectors. Manitoba Potato Production Days, Brandon, Manitoba. January 2018. (N=180). Groves, R.L. Incorporating systemic acquired resistance with aphid management. Wisconsin Seed Potato Improvement Association, Antigo, WI. January 2018. (N=68). Groves, R.L. Virus management within extended seasons. Wisconsin Potato and Vegetable Grower Association, Grower Education Conference, Stevens Point, WI. February 2018. (N=225). Groves, R.L. Disease management recommendations for non-persistent virus transmission. WERA 89 - Potato Virus and Virus-Like Disease Management meeting, Tucson, AZ. March 2018. (N=45). Groves, R.L. Potato virus Y. Antigo Agricultural Research Station Field Day, Antigo, WI. July 2018. (N=91) Groves, R.L. Prediction of Aphid Flights and Timing of Management. In Proceedings of the 2017 Wisconsin Certified Seed Potato Program, Annual Meeting Abstracts, Antigo, WI, January 2018 (http://www.potatoseed.org/). Kumar, P. and Roberts, A.G. Potatoes in Practice, James Hutton Institute's Balruddery Research farm, Dundee, Scotland, August 2017. Roberts, AG and Torrance, L. Seed Industry Event, Agriculture and Horticulture Development Board (AHDB), November 2018. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? In the past 15 years, Potato virus Y (PVY) has become the most important disease in the US seed potato industry, dramatically reducing farm profits. Factors responsible for disease emergence include changes in virus populations, changes in vector range and seasonal abundance due to climate change, changes in landscape composition, changes in cultivar selection by growers, and regulatory practices by state and federal agencies. This research has improved our understanding of the factors driving increases in new virus strains that are more difficult to control than the older strain. The new viruses are transmitted more efficiently by their aphid vectors, and they outcompete the older virus, in both the vector and the host plant, giving them a competitive advantage. This research has led to the development of improved diagnostics and management practices designed to reduce viruses in seed stocks. We have also identified various metabolic and signaling pathways important in PVY infection and host response, thus improving our understanding of mature plant resistance to viruses and potentially leading to new host resistance strategies. Objective 1: Determine whether landscape structure influences the composition of the vector community, patterns of PVY transmission, and prevalence of emerging disease [Funded by USDA]. In 5 years of virus surveys in small farms across a gradient of landscape complexity in upstate New York, we found that overall PVY prevalence in potatoes varied from 8% to 15% among years and from 0% to 45% among farms. Most farms had multiple PVY strains, but coinfections of multiple strains were rare. Across all years, we detected PVYO, PVYNWI, and PVYNO, but the recombinant PVYNTN was found most often, making up 45-50% of infections. Using ArcGIS and USDA Cropscape Data to analyze landscape composition over 5 years, we consistently found a significant positive relationship between PVY prevalence and % cropland in the local landscape, along with a negative relationship between PVY prevalence and % natural habitats. The proportion of infections caused by new recombinant strains was positively associated with vegetable crops surrounding the sampled farms. Overall PVY infection and % recombinants declined as the diversity of habitat types increased in the landscape. Aphid vector captures were compiled from the North Central Region Aphid Suction Trap Network. Data for 2005-2017 from 38 locations are available for download at: https://bugwoodcloud.org/eddmaps/csv/17035.csv. Aphid captures, weather, and landscape composition data have been analyzed to determine environmental correlates of aphid abundance and phenology. Modeling resulted in an accurate assessment of the timing of principal PVY vector flights in seed production regions of the US. Data on aphid species diversity and abundance reveal species-specific responses to landscape elements and agricultural intensity. Objective 2: Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [Funded by USDA]. Aphids may contribute to the emergence of new recombinant PVY strains. We found that aphid transmission efficiencies of PVYNTN, PVYN:O, and PVYO varied depending on the source potato cultivar. PVYO was transmitted most efficiently from mixed strain infections, so the data do not support the hypothesis that differential transmission of PVY strains from coinfections is contributing to the emergence of recombinant strains. However, winged aphids often sequentially encounter multiple strains as they test for a suitable host. We found that recombinant strains PVYN:O and PVYNTN­­ were transmitted more efficiently than PVYO when they were sequentially acquired, regardless of the order acquired. The recombinant strains may preferentially bind to the aphid stylet over PVYO or may be preferentially released during inoculation, thereby increasing the incidence of recombinant strains. To examine transmission bias, we purified the virus-encoded helper component (HC) required to bind virus to aphid stylets from 3 PVY strains and mixed different combinations with purified virus of each strain. PVYO HC plus any recombinant virus resulted in efficient transmission. PVYN:O HC also facilitated transmission of PVYO and PVYNTN, but at reduced efficiency for PVYO. PVYNTN HC did not facilitate transmission of PVYO and allowed inefficient transmission of PVYN:O. These data suggest that PVY HC specificity may aid the shift in PVY strains. Immuno-staining and confocal microscopy were used to examine spatial and temporal dynamics of strain mixtures in epidermal leaf cells of tobacco or potato. Virus binding was examined in aphid stylets following acquisition. Multiple strains co-localized in epidermal cells of both tobacco and potato. Two strains were detected binding to the distal end of aphid stylets following virus acquisition from coinfected plants. These data suggest non-antagonistic interaction between PVY strains that may explain the array of recombinant PVY strains emerging in recent years. Modeling We developed a general agent-based model for the spread of a vectored virus and ran simulations applicable to PVY in potatoes: a nonpersistent virus present at low levels in a host reservoir (seed potatoes), transmitted by aphid vectors. We examined the role of colonizing aphids versus non-colonizing aphids in spreading PVY and facilitating recombination between existing PVY strains. Sensitivity analysis suggests that prevalence depends on initial infection levels of seed potatoes, date of mature plant resistance (MPR) onset, level of resistance conferred by MPR, timing of aphid invasions, and length of the PVY latent period. Objective 3: Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [Funded by BBSRC]. Both genetic variation among host plants and ontogenetic and physiological changes within hosts leading to MPR can alter the probability of transmission and infection. There are large differences in MPR between cultivars and virus strains, but the mechanisms responsible are not well understood. We used infection assays to compare the effect of developmental stage, potato cultivar and virus strain on the probability of potato infection. Virus strain is most important, but all three variables are important. Prevalent virus strains, cultivar choice and integrated control measures are all important to PVY control. We found that MPR is highly effective against PVYO through flowering stage, but provides no protection against tuber infection by recombinant PVY strains. Thus we identified flowering as a simple marker for the onset of MPR and identified two other biochemical markers: increased oxalate levels in source leaves and reduced nitrate. However, MPR is not effective against recombinant PVY strains, so these markers are not useful for breeding. Flowering as a MPR marker is useful for farmers, but only in areas where PVYO dominates. Phloem connectivity allows PVY systemic movement at all growth stages. We carried out microarray analysis to compare PVYO and PVYNTN infection at growth stages before and after the induction of MPR. PVYO causes greater transcriptional gene changes than PVYNTN, but it is reduced in mature plants. PVYNTN induces delayed gene expression compared to PVYO. Viral titer rises more rapidly for PVYO in the initial stages of infection, despite PVYNTN reaching higher final titer in infected tissues. Several metabolic and signaling pathways have been identified as important in PVY infection and host response, including lipid metabolism. Transcriptional analysis implicates lipid remodeling in MPR. Preliminary metabolomics analysis revealed changes in structural lipids during MPR. These findings led to a project funded by BBSRC GCRF, combining MPR with potato traits suitable for Sub-Saharan Africa.

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Funke C.N., Nikolaeva, O.V., Green ,K. J., Tran, L.T., Chikh-Ali, M, Quintero-Ferrer, A., Cating, R, Frost, K.E., Hamm, P.B., Olsen, N., Pavek, M.J., Gray, S.M., Crosslin, J.M., and Karasev, A.V. 2017. Strain-specific resistance to Potato virus Y (PVY) in potato and its effect on the relative abundance of PVY strains in commercial potato fields. Plant Disease 101:20-28.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Mondal, S., Lin, Y.H., Carroll, J.E., Wenninger, E.J., Bosque-Perez, N.A., Whitworth, J.L., Hutchinson, P., Eigenbrode, S., Gray, S.M. 2017. Potato virus Y transmission efficiency from potato infected with single or multiple virus strains. Phytopathology, 107:491-498
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Mondal, S. and Gray, S.M. 2017. Sequential acquisition of Potato virus Y strains by Myzus persicae favors the transmission of the emerging recombinant strains. Virus Research, doi10.1016/j.virusres.2017.06.023
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Green, K.J., Brown, C.J., Gray, S.M. and Karasev, A.V. 2017. Phylogenetic study of recombinant strains of Potato virus Y. Virology 507:40-5
  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Mondal, S., Ghanim, M., Roberts, A., and Gray, S. 2019. Potato virus Y strains co-localize and compete in single epidermal leaf cells and can co-occupy binding sites on aphid stylets. J. Gen. Virology, in review.
  • Type: Journal Articles Status: Other Year Published: 2019 Citation: Mondal, S. and Gray, S. 2019. Strain specific properties of Potato virus Y encoded helper components provide evidence for transmission bias of recombinant strains over the ordinary strain. In preparation.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Marchetto, K. M., and A. G. Power. Coinfection timing drives host population dynamics through changes in virulence. American Naturalist 191: 173183.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Marchetto, K.M., and A.G. Power. 2018. Context-dependent interactions between pathogens and a mutualist affect pathogen fitness and mutualist benefits to hosts. Ecology.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Couture J., Singh A., Charkowski A., Groves R., Gray S., Bethke P., and Townsend P. 2018. Integrating spectroscopy with potato disease management. Plant Dis. http://dx.doi.org/10.1094/PDIS-01-18-0054-RE.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Fulladolsa AC, LaPlant KE, Groves RL, Charkowski AO. 2017. Potato Plants Grown from Minitubers are Delayed in Maturity and Lower in Yield, but are not at a Higher Risk of Potato virus Y Infection than Plants Grown from Conventional Seed. American Journal of Potato Research 95: 4553. http://dx.doi.org/10.1007/s12230-017-9613-1
  • Type: Journal Articles Status: Other Year Published: 2019 Citation: Jones, L. E., M. T. Gorczyca, and A.G. Power. Modeling the in-field spread of a vectored plant pathogen with an agent-based model. In preparation.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Shaw, A., Peace, A., Power, A., and Bosque-Perez, N. Vector population growth and condition-dependent movement drive the spread of plant pathogens. Ecology 98: 2145-2157. doi:10.1002/ecy.1907
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Marchetto, K.M., and A.G. Power. Context-dependent interactions between pathogens and a mutualist affect pathogen fitness and mutualist benefits to hosts. Ecology, https://doi.org/10.1002/ecy.2531
  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Gray, S. and Power, A. 2018. Anthropogenic influences on emergence of vector-borne plant viruses: the persistent problem of Potato virus Y. Current Opinion in Virology 33:177-183.
  • Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Shaw, A., M. Igoe, A. G. Power, N. A Bosque-Perez, and A. Peace. Modeling approach influences dynamics of a vector-borne pathogen system. In review, Bulletin of Mathematical Biology.


Progress 09/01/16 to 08/31/17

Outputs
Target Audience:Target audiences for this work include scientists and researchers in plant pathology, entomology, and ecology. In addition, potato growers are an important target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?To date, the project has provided training to seven postdoctoral scientists (2 at Cornell, 1 at the University of Wisconsin, 4 at the University of St. Andrews), one Wisconsin associate researcher, one Cornell Research Support Specialist, three Cornell graduate students (1 plant pathologist, 1 entomologist, 1 ecologist), and six Cornell undergraduate students. At Cornell University, postdocs learned techniques related to vector biology, virology and confocal microscopy. Dr. Mondal presented his research at the annual meeting of the American Phytopathological Society in August 2017 and at the International Congress of Entomology in September 2016. Five Cornell undergraduate students have worked in the Gray and Power labs to learn various techniques in virology, molecular biology and vector biology associated with the research projects. In addition, one Cornell undergraduate in mathematics has worked with Co-PI Jones to learn approaches for modeling the dynamics of insect-transmitted plant pathogens. Cornell Research Support Specialist Peters was trained in multiplex rtPCR training and protocol development at the Evolutionary Genetics Core facility (EEB, Cornell University). Peters also undertook ArcGIS and QGIS software training and protocol development at Cornell University. At the University of Wisconsin, the project continues to provide partial training and support for Associate Researcher Emily Duerr in the Department of Entomology. The Associate Researcher has recently completed a course in multivariate statistics and a short course in structured equation modeling which will be better enable the staff scientist to compile the information for spatial analyses. At the University of St. Andrews and James Hutton Institute, postdocs have been trained in new technical skills (qPCR, microarray analysis using GeneSpring and Mapman), presentation skills, and scientific writing skills. Dr. Kumar presented his research at the Biochemical Society Conference, the European Association of Potato Research meetings, and the India-Scotland Research Symposium at The James Hutton Institute. How have the results been disseminated to communities of interest?Presentations at Scientific Meetings Gray, S. 2017. Potato virus Y is seed potato's #1 problem and is an unintended consequence of science, regulators actions and farming practices. Invited seminar at the Dept of Plant Pathology, North Carolina State University, April, 2017 Groves, R.L. 2016. First principals of managing Potato virus Y. In Proceedings of the 2016 Wisconsin Certified Seed Potato Program, Annual Meeting Abstracts, January 28, 2016, Antigo, WI Groves, R.L. 2016. First principals of managing Potato virus Y. In Proceedings of the 2016 Wisconsin Certified Seed Potato Program, Annual Meeting Abstracts, January 28, 2016, Antigo, WI (http://www.potatoseed.org/). Groves, R.L., Frost, K.E. and Charkowski, A.O. 2016. Grower-driven data reveals first principles in the management of Potato virus Y incidence in seed potato production. Section Symposium Abstract of the XXV International Congress of Entomology, September 25-30, Orlando Convention Center, Orlando, FL (doi:10.1603/ICE.2016.93731). Kumar, P., Cowan. G.H., Tobin, A.K., Torrance, L and Roberts, A.G. 2016. Recombinant strains of Potato Virus Y overcome mature plant resistance in Solanum tuberosum L. 16th Triennial Meeting of the Virology Section of the European Association of Potato Research (EAPR), Ljubljana, Slovenia. Kumar, P., Cowan. G.H., Roberts, A.G., Tobin, A.K. and Torrance, L. 2017. Recombinant strains of potato virus Y overcome mature plant resistance in Solanum tuberosum. 20th EAPR Triennial Conference - PVYwide, Versailles, France, July 2017. Kumar, P., Cowan. G.H., Roberts, A.G., Tobin, A.K. and Torrance, L. 2017. Mature plant resistance in potato, its implications in PVY dynamics and management". India-Scotland research symposium, The James Hutton Institute, Dundee, Scotland UK. Kumar, P., Cowan. G.H., Tobin, A.K., Torrance, L and Roberts, A.G. 2016. The Effect of Mature Plant Resistance (MPR) on PVY Infection. Biochemical Society Conference: Taming Plant Viruses - Fundamental Biology to Nanobiotechnology, Pitlochry, Scotland, November 2016. Mondal, S., S. Gray, and M. Ghanim, 2016. Potato virus Y strains co-localize and compete in single epidermal leaf cells. Phytopathology. Abstract from APS annual meeting, August 2016. Mondal, S., and S. Gray 2017. Strain specificity of helper components encoded by Potato virus Y. Phytopathology. Abstract from APS annual meeting, August 2017. Power, A. G. "From plant communities to coinfections: Plant virus ecology at multiple scales." Wild Plant Pathosystems Meeting, University of Helsinki, Helsinki, Finland, August, 2016. Power, A. G. "From landscapes to coinfections: Plant virus epidemiology at multiple scales." Ecology and Evolution of Infectious Disease Meeting, University of California at Santa Barbara, Santa Barbara, CA, June, 2017. Grower Meetings Gray, S. Emerging potato viruses: Challenges to the seed certification process. Invited talk at the Syngenta Potato Partners Program, Torrey Pines, CA ~150 attendees, November, 2016. Gray, S. Potato virus Y management in commercial potatoes. Invited talk at the Michigan Potato Growers Conference, Mt Pleasant, MI ~ 300 attendees, January, 2017. Groves, R.L. 2016. First principals of managing Potato virus Y. In Proceedings of the 2016 Wisconsin Certified Seed Potato Program, Annual Meeting Abstracts, Antigo, WI, January, 2016 (http://www.potatoseed.org/). Kumar, P. and Roberts, A.G. Potatoes in Practice, James Hutton Institute's Balruddery Research farm, Dundee, Scotland, August, 2017. Fact Sheets Fact sheets were prepared and distributed to all growers who participated in the landscape PVY surveys in upstate New York. Commercial Meetings Groves, R.L. 2016. Potato Partners Program, Syngenta. "Advances in Colorado Potato Beetle and Potato Virus Y Management". November 16, La Jolla, CA. Torrance, L. Discussions and dissemination with Mr X Liang (director), Dr B Hu (secretary) and Dr K Xie (research development) at Xisen Potato Company Ltd., Laolong, Sgandong Province, PR China, October, 2017. Torrance, L. and Roberts, A. Preliminary discussions with French company SIPRE (Université de Picardie Jules Verne, Amiens, France) to conduct trials on the efficacy of our novel lipid-associated resistance. A non-disclosure agreement was obtained but we have decided to attempt to find funding to pursue the research further before entering into partnership with any company. Other Outreach Activities Some of findings of this project are being incorporated into discussions and other projects to develop new, resilient potato cultivars for sub-Saharan Africa. Work at the James Hutton Institute is developing a potato pathology smartphone app called Buntata (https://play.google.com/store/apps/details?id=uk.ac.hutton.ics.buntata) to help with in-field diagnostics. In time, this app will provide more than disease identification information, and we hope data from this project can be integrated in future. Discussions with staff at SASA (Science and Advice for Scottish Agriculture) have been conducted to determine how the outputs of this project with respect to disease modelling and forecasting could be fed into future practical applications to deliver integrated pest and disease management strategies. What do you plan to do during the next reporting period to accomplish the goals?In the Power lab, the spatio-temporal dynamics of PVY strains will be analyzed based on landscape studies conducted in 2012-2016 across the Finger Lakes region of New York, and several publications will be completed. The modeling work will continue testing the effects of parameters of interest (PVY strain, aphid community composition, landscape heterogeneity, aphid movement rates) on disease transmission and spread using our agent-based model. We will complete development of a mean-field (well-mixed) model to investigate competition over time between PVY strains and recombinants, parameterized using results from the Gray lab transmission studies. It will also be used to check results from the ABM, since they should produce consistent results for large, fine-grained field simulations. In the Gray lab, postdoctoral associate Dr. Mondal will complete experiments on transmission of PVY strains by Myzus persicae and confocal microscopy studies to determine how multiple strains interact at the cellular level in various potato cultivars, and how these interactions affect virus acquisition by aphid vectors. In the Groves lab, a peer-reviewed publication on the environmental correlates of aphid abundance, diversity, and phenology will be completed. In the final year of the project, the UK group will continue to study the results of the microarray data and write up publications for the data collected in previous years. We will also attempt to find further funding to pursue the candidate resistance genes we have identified.

Impacts
What was accomplished under these goals? Objective 1: Determine whether landscape structure influences the composition of the vector community, patterns of Potato virus Y (PVY) transmission, and prevalence of emerging disease [Funded by USDA]. Field surveys of aphids and PVY prevalence In 2016, we sampled PVY in potatoes on 17 farms in a gradient of landscape complexity in upstate New York. PVY was found at 88% of farms, with prevalence of 2%-38%. We detected PVYO, PVYNWI, and PVYNO, but the recombinant PVYNTN was dominant. On 10 farms, we used tobacco as a sentinel plant and found all strains. Unlike potatoes, PVYO was the most common strain and overall PVY prevalence was higher (5-45%). Using ArcGIS and USDA Cropscape Data to analyze landscape composition, we found a significant positive relationship between PVY prevalence and % cropland in the local landscape. Recombinant strains were positively associated with vegetable crops surrounding the sampled farms, and negatively associated with pasture. Overall PVY infection and % recombinants declined as the diversity of habitat types increased in the landscape. 2017 capture data of adult, alate aphids from the North Central Region Aphid Suction Trap Network have been added to the 2005-2016 dataset representing 38 locations. Similar data from various trapping devices have been provided from other states. Landscape composition surrounding NCR's aphid suction trap locations has been quantified using Cropscape. The capture database has been compiled, and data is available for researchers in the current project. Aphid captures, weather, and landscape data have been analyzed to determine environmental correlates of aphid abundance and phenology. Modeling resulted in an accurate assessment of the timing of principal PVY vector flights in seed production regions of the US. Data on aphid species diversity and abundance over varying buffer distances reveal trends in species-specific responses to landscape element identity and agricultural intensity. Objective 2: Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [Funded by USDA]. Transmission Experiments We tested the hypothesis that the recent shift in the prevalence of PVY strains is due in part to differential aphid transmission from single and mixed infections. Transmission efficiency by Myzus persicae was highest from sources infected with three virus strains, but transmission from sources infected with one or two virus strains did not differ. PVYO was transmitted most efficiently from mixed strain infection sources. There is no evidence that differential transmission of PVY strains is driving the emergence of recombinant strains. Our previous work showed that recombinant strains (PVYNTN and PVYNO) were transmitted more frequently than PVYO after sequential acquisition, regardless of the order of acquisition. When the two recombinant isolates were sequentially acquired both were transmitted at similar efficiencies regardless of the order of acquisition. This may contribute to the increased incidence of recombinant strains over PVYO in regions where multiple PVY strains are detected. To explore why PVY recombinant strains outcompete PVYO in the aphid, we studied the specificity of PVY helper component proteins in binding PVY strains to the aphid stylet, using HC and purified virus from three different PVY strains in mix and match experiments. The results indicate a strain specific function of HC, suggesting that formation of a HC-PV protein complex prior to aphid acquisition facilitates transmission. Multiple PVY strains are often found in the same field and occasionally in the same plant, but little is known about how strains interact within a plant. Immunofluorescence and confocal microscopy were used to examine the spatial and temporal dynamics of mixtures of PVY strains (PVYO + PVYNTN or PVYN) in epidermal leaf cells of tobacco or potato. Both strains systemically infected tobacco and co-localized in cells of all leaves examined; but the relative amounts of each virus changed over time. In early infections, PVYO dominated although PVYNTN was present in some cells. As infection progressed, PVYNTN became the prevalent virus and more available to feeding aphids, outcompeting PVYO. Co-localization of PVY strains was also observed in epidermal cells of potato leaves, with most cells coinfected. This allows the sharing of genetic information between viruses and the emergence of new recombinant strains. Our data do not support the dogma of spatial separation of two potyviruses and suggest apparent non-antagonistic interaction between PVY strains that could help explain the emerging recombinant strains discovered in potato in recent years. Modeling We developed a general agent-based model for the spread of a vectored virus and ran simulations applicable to PVY in potatoes: a nonpersistent virus present at low levels in a host reservoir (seed potatoes), transmitted by aphid vectors. In particular, we examined the role of colonizing aphids versus non-colonizing aphids in spreading PVY and facilitating recombination between existing PVY strains. Sensitivity analysis using a Latin Hypercube approach suggests that prevalence depends on initial infection levels of seed potatoes, date of mature plant resistance (MPR) onset, level of resistance conferred by MPR, and length of the PVY latent period. PVY is spread effectively by non-colonizing aphids, but appears to be amplified primarily by colonists. The timing of aphid invasions with respect to development and extent of MPR is also important. Objective 3: Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [Funded by BBSRC]. Experiments showed that MPR against PVY is influenced by PVY strain, host genotype and plant growth stages. There was no systemic movement of PVYO into foliar tissue at flowering stage in any cultivar tested. We found that MPR against PVYO can establish from the stolon stage onwards and is complete by flowering. Resistance was observed against PVYN and recombinant strains (PVYNTN, PVYNWi) in foliar tissues of most cultivars, but recombinant strains can infect tubers of all cultivars. This year we collaborated with SASA (Science and Advice for Scottish Agriculture) to conduct field experiments, which have corroborated the glasshouse trials. Thus recombinant strains have overcome MPR in potatoes. Solute transport studies showed no change in sink-source relationship when potato plants become resistant to PVYO. Solutes move from source leaves to tubers at flowering, explaining the lack of movement of PVYNTN and PVYNWi to non-inoculated leaves. Solute transport and unloading in tubers is functional at the flowering stage and acts to deliver recombinant PVY strains to tubers. To examine the molecular mechanism underlying MPR and how recombinant strains have overcome it, we carried out a large-scale microarray experiment analyzing the whole-genome transcript profile of plants after PVY challenge. To date, this dataset has provided three key results: 1) 35 candidate genes responsible for MPR to PVYO, including 9 uniquely expressed genes, are associated with several metabolic pathways. 2) As development progresses in healthy plants, more genes become differentially expressed. PVYNTN infection leads to suppression of this effect. Apparently, whatever the plant switches on during development to detect and suppress PVYO may be suppressed by PVYNTN, preventing MPR against PVYNTN. 3) Preliminary metabolomics analysis revealed changes in structural lipids during MPR. Application of a candidate molecule renders plants more resistant to PVY infection and a key gene in this pathway was further studied by VIGS in N. benthamiana. In preliminary studies, silencing of this lipid gene in N. benthamiana rendered plants more resistant to PVY.

Publications

  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Carroll, J.E., Smith, D. M, and Gray, S.M. 2015. Preferential acquisition and inoculation of PVYNTN over PVYO in potato by the green peach aphid Myzus persicae (Sulzer). J. Gen. Virol. 97: 797-802.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Claflin, S.B, J. Thaler, and A.G. Power. 2015. Predators, host abundance, and host spatial distribution affect the movement of wingless non-colonizing vector Rhopalosiphum padi (L.) and PVY prevalence in an oat/potato system. Arthropod-Plant Interactions 9:301309.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Claflin, S.B, L. Jones, J. Thaler, and A.G. Power. 2017. Crop-dominated landscapes have higher vector-borne plant virus prevalence. Journal of Applied Ecology 54: 11901198. doi:10.1111/1365-2664.12831.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Claflin, S.B, J. Thaler, and A.G. Power. Aphid density and community composition differentially affect apterous aphid movement and plant virus transmission. Ecological Entomology 42: 245254. doi:10.1111/een.12381.
  • Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Claflin, S.B, N. Hernandez, R. Groves, J. Thaler, and A.G. Power. Intra-annual variation and landscape composition interactively affect aphid community composition. In review, Ecosphere.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Funke C.N., Nikolaeva, O.V., Green ,K. J., Tran, L.T., Chikh-Ali, M, Quintero-Ferrer, A., Cating, R, Frost, K.E., Hamm, P.B., Olsen, N., Pavek, M.J., Gray, S.M., Crosslin, J.M., and Karasev, A.V. 2017. Strain-specific resistance to Potato virus Y (PVY) in potato and its effect on the relative abundance of PVY strains in commercial potato fields. Plant Disease 101:20-28.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Green, K.J., Brown, C.J., Gray, S.M. and Karasev, A.V. 2017. Phylogenetic study of recombinant strains of Potato virus Y. Virology 507:40-5
  • Type: Journal Articles Status: Under Review Year Published: 2018 Citation: Kumar, P., Cowan, G.H., Lacomme, C., Tobin, A.K., Roberts, A.G. and Torrance, L. Recombinant strains of Potato Virus Y overcome mature plant resistance in potato (Solanum tuberosum). In review, Phytopathology.
  • Type: Journal Articles Status: Accepted Year Published: 2018 Citation: Marchetto, K.M., and A.G. Power. Coinfection synchrony between two plant viruses increases virulence in multiple infections. In press, American Naturalist.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Mondal, S., Lin, Y.H., Carroll, J.E., Wenninger, E.J., Bosque-Perez, N.A., Whitworth, J.L., Hutchinson, P., Eigenbrode, S., Gray, S.M. 2017. Potato virus Y transmission efficiency from potato infected with single or multiple virus strains. Phytopathology 107:491-498
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Mondal, S. and Gray, S.M. 2017. Sequential acquisition of Potato virus Y strains by Myzus persicae favors the transmission of the emerging recombinant strains. Virus Research, doi10.1016/j.virusres.2017.06.023
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Shaw, A., Peace, A., Power, A., and Bosque-Perez, N. 2016. Vector population growth and condition-dependent movement drive the spread of plant pathogens. Ecology 98: 21452157, doi:10.1002/ecy.1907
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Groves, R.L., Frost, K.E. and Charkowski, A.O. 2016. Grower-driven data reveals first principles in the management of Potato virus Y incidence in seed potato production. Section Symposium Abstract of the XXV International Congress of Entomology, September 25-30, Orlando Convention Center, Orlando, FL (doi:10.1603/ICE.2016.93731).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Mondal, S., S. Gray, and M. Ghanim, 2016. Potato virus Y strains co-localize and compete in single epidermal leaf cells. Phytopathology. Abstract from APS annual meeting, August 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Mondal, S., and S. Gray 2017. Strain specificity of helper components encoded by Potato virus Y. Phytopathology. Abstract from APS annual meeting, August 2017.


Progress 09/01/15 to 08/31/16

Outputs
Target Audience:Target audiences for this work include scientists and researchers in plant pathology, entomology, and ecology. In addition, potato growers are an important target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?To date, the project has provided training to four postdoctoral scientists (2 at Cornell, 1 at the University of Wisconsin, 2 at the University of St. Andrews), one Wisconsin associate researcher, one Cornell Research Support Specialist, two Cornell graduate students (1 plant pathologist, 1 entomologist), and six Cornell undergraduate students. At Cornell University, postdoc Shaonpius Mondal (PhD, entomology) who joined the project in February 2015 is learning techniques related to vector biology, virology and confocal microscopy. Dr. Mondal presented his research at the annual meeting of the American Phytopathological Society in July 2016 and at the International Congress of Entomology in September 2016. Five Cornell undergraduate students have worked in the Gray and Power labs to learn various techniques in virology, molecular biology and vector biology associated with the research projects. In addition, one Cornell undergraduate in mathematics has worked with Co-PI Jones to learn approaches for modeling the dynamics of insect-transmitted plant pathogens. Cornell Research Support Specialist Peters was trained in multiplex rtPCR training and protocol development at the Evolutionary Genetics Core facility (EEB, Cornell University). Peters also undertook ArcGIS and QGIS software training and protocol development at Cornell University. At the University of Wisconsin, the project continues to provide partial training and support for Associate Researcher Emily Duerr in the Department of Entomology. The Associate Researcher has recently completed a course in multivariate statistics and a short course in structured equation modeling which will be better enable the staff scientist to compile the information for spatial analyses. At the University of St. Andrews, postdocs have been trained in new technical skills (qPCR, Microarray analysis using GeneSpring and Mapman), presentation skills, and scientific writing skills. How have the results been disseminated to communities of interest?Presentations at Scientific Meetings Groves, R.L. 2015. Potato Exposition. Seed Sector Breakout Session. "PVY and Other Emerging Viruses: Best Management Practices to Minimize Virus Levels in Seed Crops". January 7, Orlando, FL. Kumar, P. 2016. 16th Triennial Meeting of the Virology Section of the European Association of Potato Research, Slovenia. Kumar, P. 2016. Virology Meeting, The James Hutton Institute, Dundee, Scotland. Mondal, S. ,S. Gray, M. Ghanim, 2016. Potato virus Y strains co-localize and compete in single epidermal leaf cells. American Phytopathological Society annual meeting, August 2016. Power, A. G. 2016. Symposium on Global Science to Protect our Global Farm, American Association for the Advancement of Science, Washington, DC Power, A. G. 2016. National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, TN Power, A. G. 2016. VectorBITE Research Coordination Meeting, University of South Florida, Tampa, FL Power, A. G. 2016. Wild Plant Pathosystems Meeting, Helsinki, Finland Roberts, A.G. 2016 "Taming Plant Viruses - Fundamental Biology to Bionanotechnology", Biochemical Society, Pitlochry, Scotland. Torrence, L. 2016. Advances in Plant Virology, Association of Applied Biologists, Greenwich, UK. Torrence, L. 2016. International Plant Virus Epidemiology Symposium, Avignon. France. Grower Meetings Groves, R.L., Frost, K.E., Charkowski, A.O., Duerr, E.J., Crockford, A.B. and Huseth, A.S. 2015. Wisconsin Seed Potato Industry Association. "Influence of regional landscapes on Potato virus Y incidence in seed potato". January 28, Antigo, WI. Fact Sheets Fact sheets were prepared and distributed to all growers who participated in the landscape PVY surveys in upstate New York. What do you plan to do during the next reporting period to accomplish the goals?In the Power lab, the analysis of the field and greenhouse experiments conducted in 2016 will be completed, along with further analysis of the landscape-level data, including the spatio-temporal dynamics of the aphid community across the Finger Lakes region. In 2017 we will establish field experiments that manipulate the initial incidence of different strains to examine the probability of mixed infections and recombination, given known sources of each strain. In the Gray lab, postdoctoral associate Dr. Mondal will continue research on the sequential acquisition and inoculation of PVY strains by Myzus persicae. Specific experiments will combine different PVY strains and their helper components (a nonstructural virus protein that is required to bind virus particles to the aphid mouthparts) to determine if virus-helper component combinations are specific or if multiple PVY strains can use the helper component of one strain to facilitate their transmission. Additionally he will conduct confocal microscopy studies to determine how multiple strains interact at the cellular level in various potato cultivars, and how these interactions affect virus acquisition by aphid vectors. The Cornell modeling work will continue testing the effects of parameters of interest (aphid community composition, landscape heterogeneity, aphid movement rates) on disease transmission and spread using our agent-based model. As spatial data becomes available from experiments, these will be incorporated into models. We are also parameterizing a mean-field (well-mixed) model to investigate competition over time between PVY strains and recombinants. The model, still under development, is parameterized using results from the Gray lab transmission studies. It will also be used to check results from the ABM, since they should produce consistent results for large, fine-grained field simulations. In the Groves lab, the combination of aphid vector, weather, and landscape data will be used to determine environmental correlates of aphid abundance and phenology. This portion of the project is underway and relationships between aphid abundance and diversity will be established using multivariate analyses combined with random effects models. Outcomes will be reported in a formal submission of a peer-reviewed publication. Over the next year, the UK team will: publish a refereed journal paper on studies to date showing that recombinant PVY strains overcome MPR; analyze and validate microarray data qRT-PCR and metabolite analysis; and carry out functional validation of candidate genes or pathways involved in MPR.

Impacts
What was accomplished under these goals? Objective 1: Determine whether landscape structure influences the composition of the vector community, patterns of Potato virus Y (PVY) transmission, and prevalence of emerging disease [Funded by USDA]. Field surveys of aphids and PVY prevalence During 2015, we sampled potatoes, alternate crop hosts, and weedy relative hosts for PVY on 18 farms in a gradient of landscape complexity in upstate New York using ELISA and multiplex rtPCR. PVY was found in potatoes on all farms, with prevalence of 1% - 80%. We detected the same strains as in 2014: PVYO, PVYNTN, PVYNWI, and PVYNO; but samples were dominated by the recombinant PVYNTN. Some potatoes were co-infected with two strains, and PVY was detected in tomatoes, peppers, eggplants, and solanaceous weeds. Using ArcGIS and USDA Cropscape Data to analyze landscape composition, we found a significant positive relationship between virus prevalence in potato and % cropland within 500m, 1000m, and 1500m of the field. Recombinant strains were positively associated with vegetable crops surrounding the sampled farms, and negatively associated with legumes and grains. Both overall PVY infection and the proportion of recombinant strains declined as the diversity of habitat types within 500m increased. During 2016, we sampled potatoes and alternate hosts for PVY on 17 farms. Based on ELISA and multiplex rtPCR, PVY was found in potatoes at 15 of the 17 farms surveyed, with prevalence of 2%-38%. On 10 farms, we also conducted a survey using tobacco as a sentinel plant. All strains were found in tobacco, but PVYO was the most common strain. Nine of 10 farms had PVY, with prevalence of 5-45%. 2016 capture data of adult, alate aphids from the North Central Region Aphid Suction Trap Network have been added to the 2005-2015 dataset representing 38 locations. Similar data from various trapping devices have been provided from other states including Colorado, Maine, Minnesota, and Washington. Landscape composition at varying buffer distances surrounding each of the NCR's aphid suction trap locations has been quantified using the USDA Cropscape Data. Currently, only the NCR suction trap coordinates are readily accessible, but we are working to resolve coordinates for CO and ME traps. PRISM (Parameter elevation Regression on Independent Slopes Model) data, representing single-event, gridded mean temperature and precipitation, max/min temperatures, and dewpoints, has now been joined with aphid capture data for the indicated states. Formatted data will soon be accessible through ftp. Modeling We continue developing spatial models for virus-vector-host plant interactions. For the landscape-level models, we are using our PVY data, augmented by values gleaned from the literature to parameterize our agent-based model (describedbelow). Objective 2: Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [Funded by USDA]. Transmission Experiments We tested the hypothesis that the recent shift in the prevalence of PVY strains is due in part to differential aphid transmission from single and mixed infections. Transmission efficiencies by Myzus persicae varied depending on the potato cultivar serving as the virus source. Transmission efficiency was highest from sources infected with three virus strains, whereas transmission from sources infected with one or two virus strains did not differ. Two strains were often concomitantly transmitted by individual aphids but no aphids transmitted three strains. PVYO was transmitted most efficiently from mixed strain infection sources. There is no evidence that differential transmission of PVY strains is driving the emergence of recombinant PVY strains. Our previous work showed that sequential acquisition of two PVY strains did not always result in transmission of virus that was acquired first, suggesting that the aphid acrostyle might have strain specific binding sites. New experiments showed that recombinant strains (PVYNTN and PVYNO) were transmitted more frequently than PVYO after sequential acquisition, regardless of the order of acquisition. When the two recombinant isolates were sequentially acquired both were transmitted at similar efficiencies regardless of the order of acquisition. This suggests that sequential transmission could contribute to the recent emergence of recombinant strains. PVYNTN and PVYNO may preferentially bind to the aphid acrostyle over PVYO or they may be preferentially released during inoculation. We have begun to study the specificity of PVY helper component proteins in binding PVY strains to the aphid stylet. We are using helper component and virus from three different PVY strains in mix and match experiments. Virus binding and release from aphid stylets is monitored using fluorescent labeled antibodies. Modeling We developed a general agent-based model for the spread of a vectored virus and ran simulations applicable to PVY in potatoes: a nonpersistent virus present at low levels in a host reservoir (seed potatoes), transmitted by aphid vectors. In particular, we examined the role of colonizing aphids, which settle and reproduce on hosts, versus non-colonizing aphids, which feed briefly but do not reproduce, in spreading PVY and facilitating recombination between existing PVY strains. Sensitivity analysis using a Latin Hypercube approach suggests that prevalence depends on initial infection levels of seed potatoes, presence/absence of mature plant resistance (MPR), whether MPR confers full or partial resistance, and whether MPR develops early or later in the season. Objective 3: Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [Funded by BBSRC]. Experiments have shown that MPR against PVY is influenced by PVY strain, host genotype and plant growth stages. In Years 1-2, MPR experiments showed no systemic movement of PVYO into foliar tissue at the flowering stage in all cultivars tested. Year 3 studies indicated that MPR against PVYO can establish from the stolon stage onwards and is complete by flowering. Resistance was observed against PVYN and recombinant strains (PVYNTN, PVYNWI) in foliar tissues of most cultivars, but recombinant strains can infect tubers of all cultivars. Thus recombinant strains have overcome MPR in potatoes. CFDA translocation experiments show that there was no CFDA transport from inoculated leaves to systemic leaves by flowering, but there was still a (reduced) level of CFDA transport to tubers, sufficient to allow virus infection. Year 3 experiments showed no difference in transport prior to flowering despite earlier MPR against PVYO. We conclude that MPR against PVYO is not associated with a change in solute transport, but PVYNTN-inoculated plants had higher CFDA unloading in tubers at flowering. This supports our hypothesis that recombinant strains prolong solute unloading at flowering to enhance virus infection. GFP-tagged PVYN was studied in inoculated leaves at four developmental stages and was found to enter the phloem at all stages, suggesting that phloem entry is not a limiting step to virus infection, even at flowering when MPR protects foliar tissues. We studied the movement of PVYO by RT-PCR when plants acquired MPR. PVY can exit inoculated leaves once MPR is functional, but cannot spread to all tissues in a plant. Access to the phloem is therefore not a mechanism to control MPR. We examined the molecular mechanism underlying MPR using a comparative analysis of PVYO and PVYNTN infections. We determined the whole genome transcript profile of leaves that were inoculated with PVYNTN, PVYO and sterile water at 6-leaf (pre-MPR stage) and flowering (MPR stage). Preliminary analysis showed that a large number of genes were differentially expressed in PVYO and PVYNTN treated leaves at the 6-leaf stage compared to the same treatment at flowering.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Claflin, S.B, J. Thaler, and A.G. Power. Aphid density and community composition differentially affect apterous aphid movement and plant virus transmission. In press, Ecological Entomology.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Claflin, S.B, L. Jones, J. Thaler, and A.G. Power. Crop-dominated landscapes have higher vector-borne plant virus prevalence. In press, Journal of Applied Ecology.
  • Type: Journal Articles Status: Under Review Year Published: 2017 Citation: Claflin, S.B, N. Hernandez, R. Groves, J. Thaler, and A.G. Power. Intra-annual variation and landscape composition interactively affect aphid community composition. In revision for Ecosphere.
  • Type: Journal Articles Status: Under Review Year Published: 2017 Citation: Marchetto, K.M., and A.G. Power. Coinfection synchrony between two plant viruses increases virulence in multiple infections. In review, American Naturalist.
  • Type: Journal Articles Status: Under Review Year Published: 2017 Citation: Shaw, A., Peace, A., Power, A., and Bosque-Perez, N. 2016. Vector population growth and condition-dependent movement drive the spread of plant pathogens. In review, Ecology.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Carroll, J.E., Smith, D. M, and Gray, S.M., 2015. Preferential acquisition and inoculation of PVYNTN over PVYO in potato by the green peach aphid Myzus persicae (Sulzer). J. Gen. Virol. 97, 797802
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Claflin, S., J. Thaler, and A.G. Power. 2015. Predators, host abundance, and host spatial distribution affect the movement of wingless non-colonizing vector Rhopalosiphum padi (L.) and PVY prevalence in an oat/potato system. Arthropod-Plant Interactions 9:301309. doi:10.1007/s11829-015-9370-3
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Huseth, A.S., Peterson, J.D., Poveda, K., Szendrei, Z., Nault, B.A., Kennedy, G.G. and Groves, R.L. 2015. Spatial and temporal potato intensification drives insecticide resistance in the specialist herbivore, Leptinotarsa decemlineata. PLoS ONE 10(6):1-17. doi:10.1371/journal.pone.0127576.
  • Type: Journal Articles Status: Under Review Year Published: 2017 Citation: Mondal, S., Lin, Y., Carroll, J.E., Wenninger, E.J., Bosque-P�rez, N.A, Whitworth, J.L., Hutchinson, P., Eigenbrode, S., and Gray, S. M. 2017. Potato virus Y transmission efficiency from potato infected with single or multiple virus strains. In review, Phytopathology.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Mondal, S., Gray, S. , and Ghanim, M. 2016. Potato virus Y strains co-localize and compete in single epidermal leaf cells (abstract). Phytopathology. Abstract from APS annual meeting August 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Groves, R.L. and Huseth, A.S. 2015. Landscape management of potato pests and pathogens. In Proceedings of the 2015 University of Wisconsin - Wisconsin Potato and Vegetable Growers, Grower Education Conference, UW- Madison College of Agriculture and Life Sciences, Research Division and UWEX, Feb. 3-5, Stevens Point, WI.


Progress 09/01/14 to 08/31/15

Outputs
Target Audience:Target audiences for this work include scientists and researchers in plant pathology, entomology, and ecology. In addition,potato growers are an important target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?To date, the project has provided training to four postdoctoral scientists (2 at Cornell, 1 at the University of Wisconsin, 1 at the University of St. Andrews), one Wisconsin associate researcher, two Cornell graduate students (1 plant pathologist, 1 entomologist) and four Cornell undergraduate students. The plant pathology graduate student attended a workshop on analysis of genome and SNP data at the University of Michigan. Lab technician Peters was trained in multiplex rtPCR training and protocol development at the Evolutionary Genetics Core facility (EEB, Cornell University). Peters also undertook ArcGIS and QGIS software training and protocol development at Cornell University. Also at Cornell, postdoc YuHsuan Lin was offered and accepted a permanent research position in Taiwan. This was based partially on her postdoctoral research experience afforded by this grant. Dr. Shaonpius Mondal (PhD entomology) joined the project in February and is learning techniques related to vector biology, virology and confocal microscopy. A portion of a PhD student's thesis research involves the recombination and evolution of potato virus Y. He presented his research at the Annual meeting of the American Phytopathological Society. Four Cornell University undergraduate students worked in the Gray and Power labs to learn various techniques in virology, molecular biology and vector biology associated with the research projects. At Wisconsin, the project provides partial training and support for Associate Researcher Emily Duerr, who recently presented her findings through colloquium presentations at the University of Minnesota and the University of Wisconsin-Madison. Postdoc Ken Frost has presented portions of this research at annual meetings of the American Phytopathological Society and has recently accepted a faculty position at Oregon State University. How have the results been disseminated to communities of interest?Presentations Gray, S.M. 2014. Potato Virus Y (PVY): A rapidly changing problem for the seed and commercial potato industries. Keynote presentation, Annual meeting of the Korean and Japanese Phytopathology Societies, Busan, South Korea, October 2104 Groves, R.L., K.E. Frost, A.O. Charkowski, E.J. Duerr, A.B. Crockford and A.S. Huseth. 2014. Influence of Regional Landscapes on Potato virus Y Incidence in Seed Potato. Entomological Society of America, Annual Meeting, Portland, OR, November 2014. Power, A. G. The contribution of ecosystem services to sustainable agriculture. XI International Forum on the Protection of Nature, Naples, Italy, October, 2014. Power, A. G. Interactions between agroecology and disease ecology at multiple scales. Symposium on Agroecology, Ecological Society of America, Annual Meeting, Baltimore, MD, August, 2015. Kumar, P. Advances in Plant Virology Conference, Association of Applied Biologists, Birmingham, UK, 2015. Kumar, P. Workshop on PVY at Science and Advice for Scottish Agriculture (SASA), Edinburgh (15.01.2015). Attendance at Potatoes in Practise event at James Hutton Institute's Balruddery Research farm (13.08.2015). Large field event, wide range of stakeholders and had discussions with interested parties. Grower Meetings Groves, R.L., Wisconsin Seed Potato Industry Association, Winter Seed Meeting, Antigo, WI, February 2015. Gray, S.M. 2015. Biological and economic impacts of emerging potato necrotic viruses and the development of comprehensive and sustainable management practices. Invited speaker - Washington State Potato Growers Conference, Richland, WA. January 2015. Gray, S.M. 2015. PVY: A Problem for the US Seed Potato Industry. Invited speaker - Maine Potato conference. Presque Isle, ME. March 2015. Kumar, P. Potatoes in Practice event at James Hutton Institute's Balruddery Research farm, Dundee, Scotland, August 2015. Fact Sheets Fact sheets were prepared and distributed to all growers who participated in the landscape PVY surveys in upstate New York. What do you plan to do during the next reporting period to accomplish the goals?In the Gray lab, postdoctoral associate Dr. Mondal is continuing research on the sequential acquisition and inoculation of PVY strains by Myzus persicae. Specific experiments will combine different PVY strains and their helper components (a nonstructural virus protein that is required to bind virus particles to the aphid mouthparts) to determine if virus-helper component combinations are specific or if multiple PVY strains can use the helper component of one strain to facilitate their transmission. Additionally he is conducting confocal microscopy studies to determine how multiple strains interact at the cellular level in various potato cultivars, and how these interactions effect virus acquisition by aphid vectors. Also in the Gray lab, graduate student Washington Da Silva is continuing work on how the mode of virus transmission, either horizontal transmission by aphids or vertical transmission through tubers, affects the virus population structure over time. He is also looking at the rate of recombination when two parental strains of PVY, PVYO and PVYN, co-infect the same plant. In the Power lab, the analysis of the field and greenhouse experiments conducted in 2015 will be completed, along with further analysis of the landscape-level data, including the spatio-temporal dynamics of the aphid community across the Finger Lakes region. In 2016 we will also establish field experiments that manipulate the initial incidence of different strains to examine the probability of mixed infections and recombination. The Cornell modeling work will continue testing the effects of parameters of interest (aphid community composition, landscape heterogeneity, aphid movement rates) on disease transmission and spread in an agent-based theoretical model. As spatial data becomes available from experiments, these will be incorporated into models. Other areas of interest for the models include examining how low levels of infection in planted seed stock, coupled with small amounts of disease spread by aphid vectors and inadequate protocol for seed testing and/or saving and replanting of infected seed stock can contribute to increasing levels of infection over time. In the Groves lab, aphid capture data from the multi-year and multi-location database will be joined with the recently purchased PRISM data. Random effects associated with aphid captures will be modeled against PRISM-generated accumulated degree day (DD) data across a range of base temperatures using regression approaches. Aphid capture data will continue to be collected in the future for assembly with other participating states including Oregon. The combination of aphid vector, weather, and landscape data will be used to determine environmental correlates of aphid abundance and phenology. This portion of the project is underway and relationships between aphid abundance and diversity will be established using multivariate analyses combined with random effects models. We plan to continue investigations to evaluate the seasonal phenology of dispersing aphid species through the use of data available from aphid collection networks from the states described. By using random effects approaches to model aphid flights we can better determine the primary sources of variation that contribute to aphid flight dynamics as well as describe the similarity or differences in regional movement patterns. Over the next year, the UK team will: Publish a refereed journal paper on studies to date showing that recombinant PVY strains overcome MPR Present data at one international conference and to a stakeholder meeting Correlate our data with field trials (collaboration with SASA Edinburgh and Stewart Gray, Cornell University) Chlorophyll fluorescence studies to investigate whether such analysis would provide correlation between development stage and infection Test whether recombinant PVYNTN is more pathogenic than PVYO (in terms of increased replication and faster systemic movement). And test whether recombinant PVYNTN can prolong symplastic unloading of solutes in infected plants. These experiments will guide future experimental work on the molecular mechanism of MPR. Depending on the outcomes we will pursue metabolomics or transcriptomic analysis of potato +/- virus.

Impacts
What was accomplished under these goals? Objective 1: Determine whether landscape structure influences the composition of the vector community, patterns of Potato virus Y (PVY) transmission, and prevalence of emerging disease [Funded by USDA]. Field surveys of aphids and PVY prevalence During 2014, we sampled potatoes and alternate hosts (tomato, pepper, eggplant, solanaeous weeds) for PVY on 25 farms in a gradient of landscape complexity in upstate New York. Based on ELISA and multiplex rtPCR, PVY was found in potatoes at 17 of the 25 farms surveyed, with prevalence of 5%-50%. PCR identified PVYO, PVYNTN, PVYNWI, and PVYNO. Using ArcGIS and the USDA Cropscape Data to analyze landscape composition, we found a significant positive relationship between virus prevalence in potato and % cropland within 500m, 1000m, and 1500m of the field. Low levels of infection were found in eggplants, peppers, tomatoes and tomatillos. During 2015, we sampled potatoes, alternate crop hosts, and weedy relative hosts for PVY on 18 farms in New York using ELISA and multiplex rtPCR. PVY was found in potatoes on all farms, with prevalence of 1% - 80%. PCR detected the same strains as in 2014. A small subset of potatoes were co-infected with two strains. PVY infection was also detected in tomatoes, peppers, eggplants, and solanaceous weeds. We analyzed the diversity and abundance of NY aphid vectors in upstate New York potatoes, along with similar data collected from Wisconsin potato fields. We found higher aphid abundance and greater aphid species richness in Wisconsin than in New York, consistent with a greater proportion of agriculture in the Wisconsin landscape. Data have been compiled from the North Central Region Aphid Suction Trap Network for 2005-2013 and 38 locations comprising 218 species of aphids and nearly 1M individual captures in the upper Midwestern US. Adult alate aphid captures from a combination of trapping devices (6' suction traps, yellow sticky cards, and tile/settling traps) have been compiled from Colorado, Maine, Minnesota, and Washington. Abundance and activity of colonizing and non-colonizing winged aphids over each of these areas have been formatted into .csv formats. PRISM (Parameter elevation Regression on Independent Slopes Model) data have been purchased from the Climate Center at Oregon State University. PRISM is a set of monthly, yearly, and single-event gridded data product of mean temperature and precipitation, max/min temperatures, and dewpoints, primarily for the United States. The PRISM products use a weighted regression scheme to account for complex climate regimes associated with orography, rain shadows, temperature inversions, slope aspect, coastal proximity, and other factors. Landscape composition surrounding each of the NCR's aphid suction trap locations has been quantified for the period 2005-2014 using the USDA Cropland Data Layer for the time period for which aphid data are available. Similar data will be generated in the future for other participating states including New York. Aphid vector, weather, and landscape data will be used to determine environmental correlates of aphid abundance and phenology. Modeling We continue developing spatial models for virus-vector-host plant interactions. For the landscape-level models, we are using our PVY data to parameterize a landscape model developed previously for insect pests and adapting it for the PVY system. Objective 2: Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [Funded by USDA]. Transmission Experiments Single and mixed infections of PVYO and PVYNTN (two isolates each) were studied in three potato cultivars. In all cases virus moved easily into sink tissues (including tubers), but did not move into mature source tissues. The major difference was the ability of both strains to move and accumulate together, which was isolate and cultivar dependent. Confocal microscopy studies indicate that the success of mixed infections is related to systemic movement, not replication. We studied sequential acquisition of different PVY strains by one aphid and sequential inoculation of plants by two aphids each carrying a different PVY strain. PVYNTN was transmitted more efficiently than PVYO and the order of acquisition or inoculation did not affect the preferential transmission of PVYNTN. When a recipient plant became infected with both strains, PVYNTN maintained higher titer than PVYO. We continue to investigate other strain combinations. Aphid transmission from plants infected with 1-3 PVY strains was studied. We found that transmission efficiency is isolate not strain dependent, a single aphid can acquire multiple strains of the virus from a mixed infected plant, and the PVYO strain is more likely to be transmitted from mixed infections than other strains. Multiple strains can also be transmitted vertically through tubers, but the efficiency is virus isolate and cultivar dependent. Ongoing long-term studies are investigating the influence of vertical (through tubers) and horizontal (through vectors) transmission on virus evolution. RNA from leaf and tuber tissue will be subjected to deep sequencing and bioinformatic analysis. We used deep sequencing to compare the sequence diversity of six PVYN isolates collected on two farms in close proximity over several years. Two isolates of three other strains were also subjected to deep sequencing. Surprisingly, the PVYN isolates harbored the greatest within-isolate genetic diversity. The six isolates separated into three distinct phylogenetic clusters. Modeling In addition to our landscape model, we are testing an agent-based model for vectored viral spread between individual host plants within a field, parameterized from our recent experiments on aphid movement and host-plant preference. We are also parameterizing a mean-field (well-mixed) model to investigate competition over time between PVY strains and recombinants. The model is parameterized using results from the Gray lab transmission studies. We hope to predict future spread of PVY strains. Objective 3: Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [Funded by BBSRC]. Last year, MPR experiments showed no systemic movement of PVYO into foliar tissue at the flowering stage in all cultivars tested (Desiree, Atlantic, Maris Piper and Shepody). In addition, resistance was observed against PVYN and recombinant strains (PVYNTN, PVYNWI) in foliar tissues of all cultivars except Shepody. This year we tested PVY infection in tubers from plants inoculated at flowering stage and found that the recombinant strains can infect tubers of all cultivars. We conclude that MPR does not protect tuber infection by recombinant strains. CFDA translocation experiments to study solute transport have supported and explained the above result. There was no CFDA transport from the inoculated leaves to systemic leaves at the time the plant is flowering, but there was still a (reduced) level of CFDA transport to tubers; sufficient to allow virus infection. At flowering stage the tubers are the major sink tissue so this makes sense. GFP-tagged PVYN was studied in the inoculated leaves at four developmental stages and was found to enter the phloem at all stages, suggesting that phloem entry is not a limiting step to virus infection, even at flowering when MPR protects foliar tissues. We have tried to identify a marker for the MPR stage using FTIR. We identified two markers that correlate (oxalate levels increase in source leaves from tuber-development stage onwards, and nitrate reduces at the flowering stage). However, since we have now shown that MPR is not effective against recombinant PVY strains and these recombinants are the most prevalent infection pressure today, the use of these markers is probably of limited utility.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Groves, R.L., Frost. K.E. and Huseth, A.S. 2014. Integrating grower-driven and publically held data for improved plant protection. In Proceedings of the 2014 Joint Meeting of the American Phytopathological Society & The Mycological Society of America (APS-CPS 2014), Annual Meeting Abstracts, Phytopathology 104:S3. pp.159.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2014 Citation: Genger, R.K., Groves, R.L., Jansky, S., Rouse, D. and Charkowski, A.O. 2014. Participatory evaluation of potato varieties on organic farms: Opportunities for education and research. In Proceedings of the 2014 Joint Meeting of the American Phytopathological Society & The Mycological Society of America (APS-CPS 2014), Annual Meeting Abstracts, Phytopathology 104:S3. pp.169-170
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: Carroll, J.E., Smith, D. M, and Gray, S.M., 2015. Preferential acquisition and inoculation of PVYNTN over PVYO in potato by the green peach aphid Myzus persicae (Sulzer). J. Gen. Virol. Accepted.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Da Silva, W.L. and Gray, S.M. 2015. Changes in the population structure of PVY during systemic movement in a potato plant Phytopathology 105(Suppl. 4):S4.32
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Claflin, S., J. Thaler, and A.G. Power. Predators, host abundance, and host spatial distribution affect the movement of wingless non-colonizing vector Rhopalosiphum padi (L.) and PVY prevalence in an oat/potato system. Arthropod-Plant Interactions 9:301309.
  • Type: Journal Articles Status: Submitted Year Published: 2016 Citation: Mondal, S., Lin, Y.H., Carroll, J.E., Wenninger, E.J., and Gray, S.M. 2016. Potato virus Y transmission efficiency from different potato cultivars infected with single or multiple virus strains. Phytopathology, submitted.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Seabloom, E. W., Borer, E. T., Gross, K., Kendig, A. E., Lacroix, C., Mitchell, C. E., Mordecai, E. A., and Power, A. G. The community ecology of pathogens: coinfection, coexistence and community composition. Ecology Letters. doi: 10.1111/ele.12418
  • Type: Journal Articles Status: Submitted Year Published: 2016 Citation: Marchetto, K.M., and A.G. Power. Coinfection synchrony between two plant viruses increases virulence in multiple infections. Proc. Roy. Soc. B, submitted
  • Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: German, T.L. and Groves, R.L. 2014. New directions in pest management. In Proceedings of the 2014 University of Wisconsin - Wisconsin Potato and Vegetable Growers, Grower Education Conference , UW- Madison College of Agriculture and Life Sciences, Research Division and UWEX, Feb. 4-6, Stevens Point, WI, 27:3pps.


Progress 09/01/13 to 08/31/14

Outputs
Target Audience: Target audiences for this work include scientists and researchers in plant pathology, entomology, and ecology. In addition, potato growers are an important target audience. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Training: The project has provided training to three postdoctoral scientists (1 at Cornell, 1 at U Wisconsin, 1 at the University of St. Andrews), one Wisconsin associate researcher, two Cornell graduate students (1 plant pathologist, 1 entomologist) and two Cornell undergraduate students. The plant pathology graduate student attended a workshop on analysis of genome and SNP data at the University of Michigan. Co-PI Jones completed two biological statistics courses in order to better contribute to data analysis, along with statistical and dynamical modeling for this project. Lab technician Peters was trained in multiplex rtPCR training and protocol development at the Evolutionary Genetics Core facility (EEB, Cornell University). Peters also undertook ArcGIS and QGIS software training and protocol development at Cornell University. Professional Development: The Cornell and Wisconsin postdocs independently presented their research at the annual meeting of the American Phytopathological Society. The Cornell postdoc and plant pathology graduate student also presented their research at meetings of the plant virology community on the Cornell University campus and for the Department of Plant Pathology and Plant-Microbe Biology at Cornell University. Due in part to her work on this project, the Cornell postdoctoral scientist was offered and accepted a permanent research scientist position in the USDA, ARS equivalent in Taiwan. Similarly, the Wisconsin postdoc has recently accepted a faculty position at Oregon State University. The Cornell entomology graduate student presented her research at the annual meeting of the Entomological Society of America, the Ecology and Evolution of Infectious Disease Conference, as well as the Cornell University Ecology and Evolutionary Biology Graduate Student Symposium and the Cornell University Department of Entomology Graduate Symposium. The Wisconsin associate researcher presented her findings through colloquium presentations in both the Departments of Forest and Wildlife Ecology and Entomology at U Wisconsin. How have the results been disseminated to communities of interest? Presentations S.B. Claflin, J. Thaler, and A. Power. Landscape effects on insect community composition and disease spread in an agroecosystem. Entomological Society of America. Austin, TX. November 2013. S.B. Claflin, J. Thaler, and A. Power. Landscape simplicity affects final viral prevalence. Ecology and Evolution of Infectious Disease Conference, Fort Collins, CO, June 2014. K. E. Frost, A. S. Huseth and R.L. Groves. 2014. Using Grower-Driven and Publically Held Data for Improved Plant Protection, American Phytopathological Society, Annual Meeting, Minneapolis, MN, August 2014. R.L. Groves, K.E. Frost, A.O. Charkowski, E.J. Duerr, A.B. Crockford and A.S. Huseth. 2014. Influence of Regional Landscapes on Potato virus Y Incidence in Seed Potato. Entomological Society of America, Annual Meeting, Portland, OR, November 2014. Y. H. Lin, J. T. Ingram, S. M. Gray. Transmission efficiency of different Potato virus Y strains affecting potato from single and mixed infections. American Phytopathological Society, Annual Meeting, Minneapolis, MN, August 2014. Y. H. Lin, K. Green, A. V. Karasev, S. M. Gray. The phenotypic and genetic diversities of the ordinary strain of Potato virus Y (PVYO).? American Phytopathological Society, Annual Meeting, Minneapolis, MN, August 2014. R.L. Groves, A.O. Charkowski, S.M. Gray, A. Karasev, C. McIntosh, P. Nolte, J. Whitworth, and E. Wenninger. Development of comprehensive strategies to manage Potato virus Y in potato and eradication of the tuber necrotic variants recently introduced into the United States. Potato Exposition, San Antonio, TX, January 2014. A. G. Power. Disease ecology in plant communities. University of Michigan, Ann Arbor, Michigan, March 2014. Grower Meetings R.L. Groves, Wisconsin Seed Potato Industry Association, February 2014. R.L. Groves, Frito Lay North America, Seed Production Webinar, PVY Management, Plano, TX., February 2014. R. L. Groves, Colorado Seed Potato Growers Meeting, Managing Spread of Potato virus Y, Alamosa, CO., June 2014. S.M Gray, NYS Potato Grower meeting, January 2014. S.M Gray, Colorado Potato Grower meeting, February 2014. S.M Gray, Alaska Potato Grower meeting, March 2014 Fact Sheets Fact sheets were prepared and distributed to all growers who participated in the landscape PVY surveys in upstate New York. What do you plan to do during the next reporting period to accomplish the goals? In the Gray lab, the postdoc working on the project has left to take a permanent job in her home country of Taiwan. Another postdoc will be hired this year to continue experiments on aphid transmission of single and mixed infections of PVY and the influence of mixed infections in the movement and distribution of virus in different potato varieties that in turn influences the acquisition of virus by aphids. A current graduate student is conducting experiments on the effects of mode of transmission (vertical or horizontal) on the population dynamics and evolution of PVY populations In the Power lab, the analysis of the field and greenhouse experiments conducted in 2014 will be completed, along with further analysis of the landscape-level data, including the spatio-temporal dynamics of the aphid community across the Finger Lakes region. In 2015 we will continue to sample crops for PVY at farms in the Finger Lakes region. We will also conduct a field mesocosm experiment to examine how aphid community diversity affects transmission of PVY. The Cornell modeling work will continue testing the effects of parameters of interest (aphid community composition, landscape heterogeneity, aphid movement rates) on disease transmission and spread in an agent-based theoretical model. As spatial data becomes available from experiments, these will be incorporated into models. Other areas of interest for the models include examining how low levels of infection in planted seed stock, coupled with small amounts of disease spread by aphid vectors and inadequate protocol for seed testing and/or saving and replanting of infected seed stock can contribute to increasing levels of infection over time. The Groves lab at U Wisconsin will continue investigations to evaluate the seasonal phenology of dispersing aphid species through the use of data available from aphid collection networks from the states of Minnesota, Maine, Colorado and Washington as well as from the Rothamstad suction trap network, Rothamstad, UK. By using random effects approaches to model aphid flights we can better determine the primary sources of variation that contribute to aphid flight dynamics as well as describe the similarity or differences in regional movement patterns. Over the next year, the UK team will complete experiments to study movement of PVY strains from source leaves during MPR and begin to investigate the application of Fourier transform infrared spectroscopy to study the chemical profile of source leaves at different stages. These studies may help us to identify changes in the chemical profile of source leaves during MPR stage. We may use these chemical changes to develop markers for MPR in potato. In addition, chlorophyll florescence studies on source leaves will be carried out to determine changes in photosynthetic capacity correlating to solute availability and transport.

Impacts
What was accomplished under these goals? Objective 1: Determine whether landscape structure influences the composition of the vector community, patterns of Potato virus Y (PVY) transmission, and prevalence of emerging disease [Funded by USDA]. · During 2013, we explored the effect of landscape composition on prevalence of PVY, its aphid vectors, and their coccinellid predators in 21 farms in upstate New York. In addition, we evaluated the role of the predator and vector communities in driving virus prevalence. Using ArcGIS and the USDA Cropscape Data, to analyze landscape composition, we found a significant positive relationship between virus prevalence and percent cropland within 500m, 1000m, and 1500m of the field. There was no significant effect of the coccinellid predator community on virus prevalence in this study. · During 2014, we sampled potatoes and alternate hosts (or PVY on 25 farms in a gradient of landscape complexity in the Finger Lakes region of New York State. Plant samples have been tested using ELISA multiplex rtPCR. PVY was found in potatoes at 17 of the 25 farms surveyed, with prevalences of 5%-50%. Low levels of infection were found in eggplants, peppers, tomatoes and tomotillos. We are again using ArcGIS and the USDA Cropland Data Layer to determine the percentage agricultural land surrounding each farm. · We have monitored the abundance and activity of colonizing and non-colonizing winged aphids using the North Central Region Aphid Suction Trap Network 2005-2013 data from 45 locations. We applied generalized additive mixed models to account for the sources of variation that explain aphid phenology. We have learned that unique aphid species have similarly unique dispersal phenologies. Data from NOAA surface weather database, interpolated for each location and year, will be joined to the aphid capture data. · Landscape composition surrounding each suction trap location (i.e. 20 km buffer) has been quantified for each year using the USDA Cropland Data Layer. The combination of aphid vector, weather, and landscape data will be used to determine environmental correlates of aphid abundance and phenology. · Field-scale data has been collected and compiled for the discrete potato seed production area in northern Wisconsin, near Antigo, WI. Distance from a potato field to all other crop fields, including other potato fields, is being measured. Distance estimates can then be analyzed in relation to historical, pre- and post-harvest PVY readings to generate risk maps for production fields. · We have begun development of a set of spatial models of virus-vector-host plant interactions. For the landscape-level models, we are beginning with a landscape model that we developed previously for insect pests and adapting it for the PVY system. Data from our landscape-level PVY studies are being used to parameterize the model. Objective 2: Quantify the effects of vector community composition and seasonal movement dynamics on the spread of different strains of PVY and prevalence of strain coinfections within a field [Funded by USDA]. · Differences in transmission efficiency may be one factor driving the change in PVY strain predominance from the ordinary strain, PVYO, to the recombinant strains, PVYNO and PVYNTN. Transmission experiments were carried out using the Green peach aphid (GPA). GPA acquired virus from potato plants (cv Goldrush and NY129) infected with single (PVYO, PVYNWi, PVYNTN), double (PVYO+ PVYNO, PVYO+PVYNTN, PVYNO +PVYNTN), or triple (PVYO+ PVYNO +PVYNTN) strain mixtures. PVYNTN was transmitted more frequently than the ordinary strain, PVYO, in all sequential transmission treatments. PVYNTN was transmitted more frequently when a single aphid was given an acquisition period on both strains, in the sequential source treatments, regardless of which strain the aphid had probed on first. Both PVYNTN and PVYO were transmitted more efficiently than PVYNO when present in mixed infections with PVYNO. PVYO was transmitted most efficiently and PVYNTN the least efficiently from plants infected with all three viruses. · Potato cultivar significantly affects the outcome of the transmission experiments, and there is an isolate by cultivar interaction. We have ongoing experiments using Pike, Cal White and Goldrush. · A multiplex RT-PCR was developed to differentiate PVYO, PVYNO, and PVYNTN in mixed infections. This was used to confirm the virus strains in source tissues and those transmitted to the recipient plants. We were also able to detect PVY in necrotic, collapsed leaf tissue using ELISA and PCR. This opens up the possibility of sampling the collapsed, inoculated leaf to test for virus, rather than sampling the leaf above the collapsing leaf. In this way it would be possible to investigate early processes in the infection of a plant. · In addition to our landscape model, we are currently testing an agent-based model for vectored viral spread between individual host plants within a field, parameterized from the literature on aphid dispersal, as well as aphid movement data. We are using the model to ask whether colonizing aphids or non-colonizing aphids are more important for the rapid spread of PVY, a non-persistent virus. This model will also be used to address questions about the epidemiological consequences of mixed infections. Objective 3: Evaluate how host traits affect the probability of infection, coinfection and recombination by plant viruses [Funded by BBSRC]. · Early (Atlantic and Shepody) and late maturing (Maris Piper and Desiree) cultivars of potato were challenged by manual inoculation at four different developmental stages (6 leaf, stolon development, tuber development and flowering) with different PVY strains (PVYO, PVYN,PVYNWi,PVYNTN). We found that MPR initiated at different developmental stages depending on the potato cultivars and viral strains. The cultivar Desiree was resistant to systemic infection with PVYO and only 13% of Desiree plants at the 6 leaf stage (24-26 DAP) became infected with PVYN. In experiments with PVYN resistance initiated at stolon development stage (36-40 DAP) in cv Maris Piper, and it was almost completely resistant during the flowering stage. On the other hand, cultivars Atlantic and Shepody remained susceptible to PVYN infection and only cv. Atlantic showed resistance at flowering stage (77-81 DAP). In experiments with PVYO resistance initiated during the stolon development stage (36-40 DAP) in all cultivars, and plants were almost completely resistant at the tuber development stage (51-52 DAP). · Studies on the transport of carboxyfluorescein diacetate (CFDA) during tuber development and flowering were initiated to investigate source-sink relationships and correlate this with systemic virus movement. CFDA was unloaded into tubers of all cultivars at the tuber development stage but unloading was markedly decreased during the flowering stage of cvs. Maris Piper and Atlantic. Taken together these results indicate that there is variation in MPR onset against different PVY strains, implying that MPR is specific to different viral strains. There is clearly interplay of host genotype, virus pathogenicity and possibly host plant physiology influencing the MPR response in potato. · Based on these experiments, data suggested that PVY strains may be differentially impeded in entering the phloem tissue at different stages depending on the cv. Therefore, we studied movement of PVY into the vascular tissue using a green fluorescent PVYN clone: PVYN605-GFP (the only GFP-tagged clone available at present) at four stages of development. Experiments have been completed for the first three stages and flowering-stage work is ongoing.

Publications