Source: NORTH CAROLINA STATE UNIV submitted to
INTEGRATED DISEASE MANAGEMENT IN ORGANIC AND CONVENTIONAL STRAWBERRY AND VEGETABLE PRODUCTION SYSTEMS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1013724
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2017
Project End Date
Sep 30, 2022
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Entomology and Plant Pathology
Non Technical Summary
Growers, and supporting industries, NGOs and other agencies, face multiple challenges to assure sustainable production of specially crops such as vegetables and strawberries. Advances are best served through innovative approaches that develop new scientific knowledge and integrate this knowledge into products, outcomes, outputs and practices that reduce risk due to plant pathogens and improve farming systems. This project will be part of a national coordinated effort (With NC State University as the lead institution) to determine the utility of grafting as a tactic to manage soilborne pathogens and increase productivity in fruiting vegetable production systems. This includes the design of farming systems that optimize benefits for growers, the environment and consumers. This project will also conduct research, extension and training programs to design integrated systems to manage tomato and strawberry soilborne pathogens and major pathogens that affect the fruit and foliage of these specialty crops. Project priorities and activities will be done in a participatory way with stakeholders and collaborating partners. Knowledge and recommendations will be developed that impact organic and conventional commercial growers as a primary audience and knowledge will also be translated to private industry, NGOs, other agencies and public policy leaders to advance their missions. This work will contribute to food security at the local to national level, enhance profitability of existing and new business and seek to advance the sustainability of agricultural systems.
Animal Health Component
50%
Research Effort Categories
Basic
20%
Applied
50%
Developmental
30%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2121122116020%
2121499116040%
2051499116010%
2051122116010%
2121499302010%
2121122302010%
Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 205 - Plant Management Systems;

Subject Of Investigation
1499 - Vegetables, general/other; 1122 - Strawberry;

Field Of Science
1160 - Pathology; 3020 - Education;
Goals / Objectives
The mission of our work is to advance the science of plant pathology and farming systems research; then translate scientific advances into useful knowledge, methods and products that affect the practice of disease management and sustainable agriculture in specialty crop systems (vegetables and strawberries).The main goals are to:Determine the utility of grafting as a tactic to manage soilborne pathogens and increase productivity in fruiting vegetable production systems. This includes the design of farming systems that optimize benefits for growers, the environment and consumers.Design integrated systems to manage tomato pathogens with emphasis on:Soilborne pathogens and fruit and foliar pathogensDesign integrated systems to manage strawberry pathogens with emphasis on:Soilborne pathogens and fruit and foliar pathogens
Project Methods
Advances in vegetable grafting will be accomplished through the management of a large multi-state, transdisciplinary, industry driven and highly participatory project coordinated by NC State University as the lead agency. This will include the integration of research, extension and education activities, outcome and outputs. NC based activity will include field experiments using standard experimental designs and primarily in close cooperation with growers and other stakeholders to identify and address priority challenges and opportunities. Work will also include lab, greenhouse and growth-chamber experiments conducted by graduate students, undergraduate students, postdocs and/or other scientific trainees and technicians. Outcomes and outputs will be disseminated for national and international utilization.Advances in management of tomato and strawberry soilborne, fruit, and foliar pathogens will be accomplished through field, lab, greenhouse and growth chamber experiments using traditional and novel (molecular-based) experimental protocols. Some of the work will be done on a regional basis by undergraduate, graduate and postdoctoral students, technicians or other scholars. Outcomes and outputs will be disseminated primarily for state and regional advantage but will have national and international impact.

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Our program is structured as an integrated research and extensionprogram with periodic opportunities to teach. Primary target audiences are stable over the life of the project and include: 1) CES agriculture agents - through training programs and one-on-one support of information or through cooperative projects. Training programs are local to national in scope. 2) Other professionals, train-the-trainer leaders, and consultants who support the industry through formal and informal connections and programs; 3) Strawberry, tomato and other vegetable growers with a focus on NC but also in the southeast and along the eastern seaboard. Program impacts extend to other stakeholders in diverse regions of the USA and internationally; 4) Industry professionals through collaborative projects, evaluation of emerging products or technologies, and by providing scientific and extension information related to program outcomes and outputs; 5) Students in NC or across the USA through formal lectures and/or informal interactions in support of their educational experience; 6) Scientific colleagues through published products, scientific conferences, shared leadership to advance the science and practice of the discipline, and through service in professional societies, on grant panels, journal editorial responsibilities and other interactions. 7) General public and policy makers through educational programming opportunities. Changes/Problems:NONE What opportunities for training and professional development has the project provided?Training the next generation of scientists. We trained 3 undergrads, 3 grad students (directly), 5 grad students (as a committee member but highly engaged in project goals), and 2 senior research scientists during the reporting period. We interact with a wide diversity of CES agents in formal and informal settings to enhance their professional development. How have the results been disseminated to communities of interest?Our program updated materials for the strawberry grower portal (https://strawberries.ces.ncsu.edu/ e.g. see resources), IPM portal (https://ipm.ces.ncsu.edu/), vegetable grafting (vegetablegrafting.org) and other outlet sources for immediate use by growers. We met with Southern Region Plant Pathologists and compiled the new IPM guide for strawberries for 2018 with major changes to our guide and updated the SoutheasternUSVegetable Crop Handbook. These incorporate our up-to-date research-based information and are widely used by grower sin the Southeastern USA. Many tomato and strawberry samples were diagnosed through the clinic and QoI fungicide resistance was found in some 'acutatum' strains in NC. A large number of presentations were made to disseminate knowledge. Popular Press Articles: New herbicide registration for weed control in watermelon crops recommended. 2018. Science News. https://www.sciencedaily.com/releases/2018/08/180829115542.htm. NC State Team Helped Growers Transition Away from Methyl Bromide. 2017. R. Hallberg and D. Shore. CALS News Bulletin. https://cals.ncsu.edu/news/nc-state-team-helped-growers-transition-away-from-methyl-bromide/; https://ipmsouth.com/2017/11/21/ncsu-transition-team-for-methyl-bromide-helps-growers-maintain-yields-while-improving-the-ozone-layer/ IPM Leader receives Excellence in Extension Award. R. Hallberg. Southern IPM Center. Sept 15, 2017. https://ipmsouth.com/2017/09/15/ipm-leader-receives-excellence-in-extension-award/; https://www.apsnet.org/MEMBERS/AWARDS/EXCELLENCEEXTENSION/Pages/FrankJLouws.aspx Use advisory tool and links to guide strawberry disease managementdecisions. R. Hallberg. Southern IPM Center. May 1, 2017. https://ipmsouth.com/tag/botrytis-fruit-rot/ Southeastern Strawberry Growers Advised to Prepare for Disease Pressure. D. Eddy. Growing Produce. May 2, 2017. http://www.growingproduce.com/fruits/berries/southeastern-strawberry-growers-advised-to-prepare-for-disease-pressure/; http://www.hortidaily.com/article/34360/Tools-to-guide-strawberry-disease-management-decisions. Extension Presentations: Tomato/Vegetables: Fruit Expo, Myrtle Beach, SC. Dec 4 2018. T. Ingram and F.J. Louws. Rootstock variety trials for bacterial wilt and Verticillium race 2 management. Mills River Tomato Field Day. J. Kressin, T. Ingram and F.J. Louws. Aug 16, 2018. Pruning, pinching and plant spacing to optimize grafted tomato production. Mills River Tomato Field Day. T. Ingram, I. Meadows and F.J. Louws. Aug 16, 2018. Grafting of Vegetables: Update of on-farm trials. T. Ingram, I. Meadows and F.J. Louws. 49th NC Tomato Growers Association Annual Meeting and Winter Vegetable Conference Asheville, NC Feb 21, 2018. Grafted Tomatoes for Disease Control and Production. 30th Annual Southeast Vegetable and Fruit Expo, Myrtle Beach, SC. November 29, 2017. F.J. Louws and I. Meadows. Grafting tomatoes: Impact on Tasti-Lee, Mills River Tomato Field Day. T. Ingram, J. Kressin, I. Meadows and F.J. Louws. Aug 10, 2017. NC Tomato Growers Meeting. Hands-On Grafting with Tomato and Watermelon, NCSU Grafting Graduate Student Team Members Jonathan Kressin. Feb 8 2017. Vegetable Grafting and the Land Grant Experience: Linking Innovation, Research, Education and Extension. Capital Hill Ag Research Congressional Exhibition & Reception, Association of Public and Land-grant Universities. April 5, 2017. Integrated Management Practices to Control Bacterial Spot of Tomato. 2017. Mid-Atlantic Fruit and Vegetable Convention. Hershey PA. February 2, 2017. Integrated management of vegetable diseases. 2017 Horticulture Industries Conference and Trade Show (AR/OK). Fayetteville, AR. 13 January 2017. Louws, F.J. Vegetable grafting as a production tool to manage diseases and increase yields. 2017 Farm School Summit. Mountain Horticulture Crops Research and Extension Center. Mills River, NC. Sept 15, 2017. Strawberries: Integrated Disease Management of Strawberries: Progress over Time and Lessons Learned. Southeast Strawberry Expo. 9 Nov, 2018. Winston Salem NC. Emerging problems with fungicide resistance to manage Botrytis and Anthracnose. Ontario Fruit and Vegetable Convention (Berry Growers of Ontario). Niagara Falls ON. Feb 21, 2018. Managing Anthracnose: Current work on host resistance, forecasting models and other IPM tactics. Ontario Fruit and Vegetable Convention (Berry Growers of Ontario). Niagara Falls ON. Feb 20, 2018. Louws F.J., C Johnson and G. Schnabel. Strawberry Disease Management. Southeast Strawberry Expo. 2 Nov, 2017. Wilmington NC. Louws, F.J. Strawberry Preplant Meetings: Strawberry disease update. Nash Co. Aug 15, 2017; Johnson Co. Aug 29, 2017. (Pre-recorded video). Louws, F.J. Integrated management of strawberry (fruit) diseases. 2017 Horticulture Industries Conference and Trade Show (AR/OK). Fayetteville, AR. 13 January 2017. Integrated management of Strawberry diseases. 2017 AR Strawberry Growers Association. Conway, AR. 12 January 2017. What do you plan to do during the next reporting period to accomplish the goals?The work to date hasbeen very productive. We plan to continue working on our HATCH goals consistent with the trajectory of this reported information.

Impacts
What was accomplished under these goals? GOAL 1: Determine the utility of grafting as a tactic to manage soilborne pathogens and increase productivity in fruiting vegetable production systems. This includes the design of farming systems that optimize benefits for growers, the environment and consumers. (see also USDA-SCRI vegetable grafting ReePORTS). GOAL 2. Design integrated systems to manage tomato pathogens with emphasis on soilborne pathogens and fruit and foliar pathogens. Verticillium Wilt Work: Multiple tomato lines were planted in a Verticillium hot field near Mills River NC, to test their ability to resist or tolerate V. dahliae (Vd) race 2. The study included 33 combinations of standalone rootstocks and rootstocks/scions (susceptible line 'Red Defender') secured from world-wide sources. Several non-grafted rootstocks showed extraordinarily low amounts of damage from Vd. However, it should be noted that low levels of disease on the non-grafted rootstocks was not a good predictor of how well these rootstocks behaved when grafted to Red Defender. The best example of this was 7-1k (an NCSU breeding line) which had virtually no disease on the non-grafted plants. When grafted to Red Defender as the rootstock, the disease ratings for 7-1k were an order of magnitude higher, and statistically grouped with almost all the controls. This indicates that even the most resistant rootstocks may not be able to prevent the fungus from attacking the scion. Resistance to Verticillium was not highly correlated with overall yield. This would imply that tolerance/vigor is a more important factor in rootstocks than resistance. Maxifort is a good example of a rootstock with medium levels of resistance, but generated high yield in the scion. Despite having statistically similar levels of disease in scions grafted to H7998 (a parent to many disease resistant rootstocks), scion grafted to Maxifort had twice the yield. More research is needed to understand the dynamics between vigor, tolerance, and resistance, in relation to yield. Overall Maxifort, OH-316, and 7-1k. 7-1k conferred a high level of tolerance to Verticillium, bacterial spot, and early blight. Tomato Rootstock Variety Trials for Bacterial Wilt Resistance: We performed a five-location (across NC) to test for bacterial wilt (Ralstonia solanacearum) resistance and yield on a total of 12 rootstocks, grafted with locally recommended scion cultivars, and a non-grafted susceptible control. We worked closely with the Tri-Hishtil vegetable grafting company in Mills River, NC. They donated most of the grafted plants used in these experiments, while the NCSU Grafting team provided the rest. We tested predominantly 8-12 plant plots with 4 replications in Jackson, Rowan, Pender, and Brunswick counties in fields with a history of moderate to very strong bacterial wilt disease pressure, as well as a no-disease contrast at the Mountain Research Station in Waynesville. We experienced very strong disease pressure (100% loss of non-grafted susceptible) and good rootstock contrasts at the Jackson and Pender co. locations and very low disease pressure with no contrasts in the Rowan and Brunswick fields. The top rootstock performers for resistance were 'Shin Cheong Gang' and DR6258TX (Seminis), 'CRA66' (open-pollinated), 'Armada' (Takii Seed), and two NCSU breeding lines. Others that performed well but less consistently were 'RST-04-106-T', 'BHN 1087', and 'Hawaii 7998'. 'Bowman' performed well in Jackson, but not in Pender. 'Shield' performed better than the non-grafted susceptible, but did poorer compared to other resistant rootstocks, and one of the NCSU lines was no different from the control. Many of the rootstocks performed equally well with regards to yield and fruit weight. Generally, the relative yield contrasts at each location were similar for fruit size, and were mostly affected by the severity of wilting; the most resistant yielded the best. In the absence of disease, we did not observe yield increases over the non-grafted susceptible; they were the same. The open-pollinated 'CRA66' performed very well for fruit size and yield/acre, but had significantly lower yield in the Piedmont, which may mean it does not tolerate the heavy clay of that region as well as other rootstocks. While having good resistance, 'Hawaii 7998' consistently exhibited vigor and yields on the lower end or significantly lower than the other rootstocks, which is consistent with our data from previous years, suggesting it is not a superior rootstock for NC with regards to yield. In the presence of low disease, 'Shield' yielded well, but yields began to decrease under strong disease pressure due to plant losses and a general reduction in average fruit size. Advances with Early Blight of Tomato: We collected 100 strains of the early blight pathogen (presumably Alternaria solani, but we discovered they were all A. linariae) from NC. We isolated the DNA and continue analysis. In the long run, we will assess the genetic diversity and pathogenicity of these strains. This data then will be used to optimize management and breeding programs. Tomato Bacterial Spot Research: We also collected nearly 300 strains of the Xanthomonas bacterial spot pathogen. To date we characterized these for copper resistance and streptomycin resistance. Nearly 96% of the stains are resistant to copper and about 26% to streptomycin. This suggests streptomycin is still an important tool in transplant production; copper is not helpful. We will type these strains for their race profile and diversity so this information can guide breeding programs to prioritize resistance to the most important strains in NC. We also worked with Florida to type the races and assess diversity. This work is being facilitated by a grad student. This project is nearly complete. GOAL 3: Design integrated systems to manage strawberry pathogens with emphasis on soilborne pathogens and fruit and foliar pathogens. ?Strawberry Pathology and IPM Programs: We updated the software and extension information related to the forecasting system (https://ipm.ces.ncsu.edu/strawberry-fruit-infection-risk-tool/). We will continue to tweak and revise the system. We also did functional assays of strawberry selections to determine if certain strawberry cultivars suppress Colletorichum infections in the green leaf tissue. This is a primary mechanism by which the pathogen moves with green plants and builds inoculum loads (asymptomatically). We found one line that seems to suppress both Colletotrichum gloeosporioides (Cg) and C. acutatum (Ca) (NCS 10-147) colonization of the green tissue. This project sat idle for while with the departure of Dr. Jeremy Pattison, Ray Jacobs and Dr. Tika Adhikari. Complex analysis of gene expression profiles are being analyzed. In the meantime, we developed a collaboration with Dr. Gina Fernandez and her graduate student and did a lot of field-based work to further select Colletotrichum resistant lines based on the previous work we did. This also was a large data set of information and needs further analysis.

Publications

  • Type: Other Status: Published Year Published: 2017 Citation: Louws, F.J. (Managing editor) 2013-2017. Management of Strawberry Diseases. IN Southeast Regional Strawberry Integrated Management Guide. (GA, SC, TN, NC).
  • Type: Other Status: Published Year Published: 2017 Citation: Louws, F.J. and C. Johnson. 2017. Efficacy of fumigants or fumigant combinations for managing soilborne nematodes and diseases, and weeds. 2017. IN: Southeastern U.S. 201 Vegetable Crop Handbook
  • Type: Other Status: Published Year Published: 2018 Citation: Louws, F.J. 2013-2018. Strawberry disease control. IN: North Carolina Agricultural Chemicals Manual. (Annual Updates).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Bertucci, M., K. Jennings, D. Monks, D. Jordan, J.R. Schultheis and F.J. Louws. 2018. Effect of Palmer amaranth (Amaranthus palmeri) density on yield of grafted and nongrafted watermelon on weed seed production. Weed Sci. Soc. America Abstracts.
  • Type: Other Status: Published Year Published: 2018 Citation: Melanson et al. 2018. (Louws as Author 2018). Management of Strawberry Diseases. IN Southeast Regional Strawberry Integrated Management Guide. (GA, SC, TN, NC).
  • Type: Other Status: Published Year Published: 2018 Citation: Louws, F.J. 2018. Strawberry disease control. IN: North Carolina Agricultural Chemicals Manual.
  • Type: Other Status: Published Year Published: 2018 Citation: Louws, F.J. and C. Johnson. 2018. Nematode control in vegetables. IN: North Carolina Agricultural Chemicals Manual. (Annual Updates) AND Southeastern U.S. 2018 Vegetable Crop Handbook.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Bertucci, M., D.H. Suchoff, K. Jennings, D. Monks, C.C. Gunter, J. and F.J. Louws. 2018. Comparison of root system morphology of cucurbit rootstocks for use in watermelon grafting. HortTechnology 28:628-636.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Bertucci, M., Jennings, K., Monks, D., Jordan, D., Schultheis, J., Perkins-Veazie, P., Louws, F.J, and Jordan, D.L. 2018. Early season growth, yield, and fruit quality of standard and mini watermelon grafted onto several commercially available cucurbit rootstocks. HortTechnology 28:459-469.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Bertucci, M., Jennings, K., Monks, D., Jordan, D., Schultheis, J., Louws, F., & Waldschmidt, M. 2018. Effect of Bicyclopyrone on Triploid Watermelon in Plasticulture. Weed Technology, 32(4), 439-443. doi:10.1017/wet.2018.36.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Suchoff, D.H., C.C. Gunter, J.R. Schultheis, M.D. Kleinhenz and F.J. Louws. 2018. Rootstock effect on grafted tomato transplant shoot and root responses to drying soils. HortScience 53:1586-1592.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Suchoff, D.H., J.R. Schultheis, M.D. Kleinhenz, F.J. Louws and C.C. Gunter, 2018. Rootstock improves high-tunnel tomato water use efficiency. HortTechnology 28:344-353.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Suchoff, D.H., P. Perkins-Veazie, H.W. Sederoff, J.R. Schultheis, M.D. Kleinhenz, F.J. Louws, and C.C. Gunter. 2018. Grafting the indeterminate tomato cultivar moneymaker onto multifort rootstock improves cold tolerance. HortScience 53: 1610-1617.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Chaudhari, S., K.M. Jennings, D.W. Monks, D.L. Jordan, C.C. Gunter and F.J. Louws. 2017. Response of drought-stressed grafted and nongrafted tomato to postemergence metribuzin. Weed Technology 231:447-454.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Rahman, M., and F.J. Louws. 2017. Epidemiological significance of crown rot in the fruiting field in relation to Colletotrichum gloeosporioides infection of strawberry nursery plants. Plant Disease 101: 907-915. https://doi.org/10.1094/PDIS-06-16-0802-RE
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Chaudhari, S., K.M. Jennings, D.W. Monks, D.L. Jordan, C.C. Gunter and F.J. Louws. 2017. Absorption, translocation, and metabolism of 14C-halosulfuron in grafted eggplant (Solanum melongena) and tomato (Solanum lycopersicum). Weed Technology 31:908-914.
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: Cohen, R., A. Dombrovsky and F.J. Louws. 2017. Grafting as agrotechnology for reducing disease damage. IN: G. Colla, F. Perez-Alfocea and D. Schwarz. Eds. Vegetable Grafting: Principles and Practices. CABI. pg 155-170.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Gao, A. T.B. Adhikari and F.J. Louws. 2018. Identification and characterization of Fusarium oxysporum f. sp. lycopersici from greenhouse tomatoes in North Carolina. NC State University 17th Annual Summer Undergraduate Research Symposium. July 31, 2018.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Suchoff, D., P. Perkins-Veazie, H.W. Sederoff, J.R. Schulthuis, M.D. Kleinhenz, F.J. Louws and C.C. Gunter. 2018. Improving tomato cold tolerance through grafting. HortScience 53:S98.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Suchoff, D., F.J. Louws, J.R. Schulthuis, M.D. Kleinhenz and C.C. Gunter. 2018. Grafted tomato shoot and root responses to drying soils. HortScience 53:S97.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Suchoff, D., C.C. Gunter, M.D. Kleinhenz J.R. Schulthuis, and F.J. Louws. 2018. Thirst quenching: improving tomato water use efficiency through grafting. HortScience 53:S487
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Ingram, T., R. Dean and F.J. Louws. 2018. Optimizing genetics to manage verticillium wilt in tomatoes through traditional breeding and grafting: An elusive challenge. APS/Conference on Soilborne Pathogens Abstracts 2018.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Fenstemaker, S., N. Huarachi Morejon, M. Masud, M. Kleinhenz, S. Wedryk, F.J. Louws and David Francis. 2018. Vigor, resistance, and rootstocks. 47th Tomato Breeders Roundtable. April 2018
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Kressin, J. D.R. Panthee, F.J. Louws, M. Planas, N. Sanchez-Coll and M. Valls. 2018. 4-dimensional colonization dynamics of the grafted tomato-bacterial wilt pathosystem and their implications for resistance selection. 47th Tomato Breeders Roundtable.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Adhikari, P., D. R. Panthee, H. Ashrafi, C.C. Gunter, F.J. Louws, and C. Arellano. 2018. Mapping QTL derived from S. pimpenellifolium LA3707 for bacterial spot resistance against race T4. bacterial spot of tomato: pathogen story and our efforts of tomato improvement in NC. 47th Tomato Breeders Roundtable
  • Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Kressin, J. M. Planas, D.R. Panthee, F.J. Louws, N. Sanchez-Coll and M. Valls. 2018. Spatiotemporal dynamics of colonization by Ralstonia solanacearum in grafted tomatoes. Graduate Student Research Symposium. NC State University.