DEVELOPMENT OF RISK ALGORITHMS FOR THE NORTHERN ROOT-KNOT NEMATODE IN POTATO IN NEW YORK STATE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1015439
• Grant No.: 2018-67011-28072
• Cumulative Award Amt.: $92,812.00
• Proposal No.: 2017-07043
• Project Start Date: Apr 1, 2018
• Project End Date: Jul 22, 2019
• Grant Year: 2018
• Program Code: [A7101]- AFRI Predoctoral Fellowships

Recipient Organization
N Y AGRICULTURAL EXPT STATION
(N/A)
GENEVA,NY 14456

Performing Department
Plant Path/Plant Microbe Biol

Non Technical Summary
The Northern root-knot nematode (RKN; Meloidogyne hapla) is a microscopic roundworm found in agricultural fields that parasitizes potato and other important vegetable crops. In New York State and the northeastern U.S., RKN is associated with potato tuber damage and yield reductions. RKN populations within the soil are often controlled by applications of pesticides, either fumigant or non-fumigant nematicides, to reduce the population. Decisions surrounding these pesticide applications for nematode control are often routine and prophylactic, driven by the assumption of the ubiquitious presence of the nematodes, even when true population tallies are not known to the grower. These treatments may be unneccessary if the RKN population in the soil is insufficient to cause measureable economic damage. This situation may be described as a "false positive decision" (when a nematicide is applied, but population tallies do not justify it's use). This approach increases production costs by increasing inputs, maintains selection pressure of on pathogen populations in the soil (potentially developing RKN populations insensitive to the nematicide), and potentially has deleterious effects on the environment and surrounding communities. Predicting disease caused by RKN and other plant-parasitic nematodes is strongly reliant upon effectively quantifying the populations within the soil. Traditional techniques for doing this include Whitehead trays and Baermann funnels. However, these techniques are time consuming (taking days to weeks), potentially underestimate true populations, and are technically challenging, requiring nematode identification by an experienced nematologist. These factors can lead to significant challenges and time-lags in delivering robust disease risk predictions. This project addresses this problem by seeking to develop a pre-plant, DNA-based soil test for RKN that produces rapid and accurate results. This will be accomplished by quantifying the relationship between soil DNA prior to planting and RKN populations. Subsequently, this information will be related to yield loss and crop damage observed in potato to investigate economic thresholds for RKN. The synthesis of this information into a disease risk algorithm will help inform when RKN populations justify pesticides use.To acheive the over-arching goal of reducing crop loss from nematode parasitism in potato by developing risk algorithms for improving pre-plant risk prediction, the project will focus on three areas of research.Firstly, the project will develop a DNA-based test to detect and quantify RKN directly from the soil, bypassing the length traditional methods. The DNA-based test, called a quantitative polymerase chain reaction assay, will selectively measure the species of interest (M. hapla) by detecting a specific gene possessed by the nematode. DNA isolated from field soil will be measured using using this test, and unknown populations will be compared to known population standards, to quantify pathogen loads in the soil.Secondly, the relationship between RKN populations and crop damage will be investigated by conducting on-farm sampling and controlled field experiments. Three commercial potato fields in New York with a known history of RKN will be selected, and soil samples collected from 100 points within each of the fields, prior to planting. Nematode populations will be quantifyied from the soil at each of the sampling locations ('initial' population). At harvest, the yield at each sampling location will be assessed by measuring tuber weight and scoring tuber damage. Soil samples will again be collected at harvest to again measure RKN populations ('final' population). Crop yield will be plotted against the initial RKN population and regression analysis performed to assess the relationship between the two variables. The relationship between RKN populations and crop damage will also be investigated by conducting a controlled field experiment. Within this, potato plants will be infected at the start of the growing season with a known number of RKN in controlled experimental plots. This initial infection rate will be made at five population densities (125, 250, 500, and 1,000 RKN individuals per plant, plus a non-infected control). At harvest, the yield at each plot will be assessed by measuring tuber weight and scoring tuber damage. Soil samples will also be collected from each plot to assess final populations. Crop yield will be plotted against initial RKN populations and regression analysis performed to assess the relationship between the two variables. Thirdly, to help inform the level of disease risk, the susceptibility of commercial potato cultivars to RKN will be evaluated in the greenhouse. Eleven fresh-market potato cultivars commonly grown in New York will be selected for use in the study, and a susceptible tomato variety will be included as a positive control. Potatoes will be planted in the greenhouse in sterilized soil. Following sprouting, plants will be infected at one of three population densities (500 or 1,000 RKN individuals per plant, plus a non-infected control). Plants will be maintained in the greenhouse for nine weeks, after which they will be harvested, and data on total yield, tuber damage, number of tubers, and final population of nematodes per pot will be gathered. Differences between cultivar types will be investigated using regression analysis. Knowledge gained in this experiment will help inform disease risk and cultivar selection under high nematode population pressure. Target audiences for dissemination of this include potato growers, industry stakeholders, agricultural consultants, and cooperative extension personnel. Research findings generated in this project will be disseminated through proven content delivery methods and engagement of growers with experiential learning activities. Formal outreach efforts will include using programming and networks maintained by Cornell Cooperative Extension to maximize impact and scope of dissemination. Results will be presented orally at extension events, field days, and expos. Information will be published and distributed as written materials, including factsheets and news bulletins within Cornell's VegEdge newletter. This information will also be suitable for delivery through eXtension (https://extension.org). Informal outreach efforts will include on-farm consultations with commerical growers participating in the on-farm soil sampling. This project will support the development of a decision support system for improved control of RKN and other plant-parasitic nematodes, leading to more informed disease management decision making on the farm. This will potentially reduce the cost of inputs and enable conservative, targeted pesticide useage, thus reducing off-target deleterious impacts to the environment and communities. Outcomes will also contribute to enhanced resilience of rural communities by maximizing the return on investiment by growers made for disease control.

Animal Health Component

60%

Research Effort Categories

Basic

20%

Applied

60%

Developmental

20%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1310	1170	50%
216	4099	1120	50%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants; 216 - Integrated Pest Management Systems;

Subject Of Investigation
1310 - Potato; 4099 - Microorganisms, general/other;

Field Of Science
1120 - Nematology; 1170 - Epidemiology;

Keywords

dna quantification

northern root-knot nematode

action thresholds

extension

potato

risk assessment

Goals / Objectives
GoalThe defining goal of this project is to reduced crop loss from nematode damage in potato by the development of risk algorithms for improving pre-plant risk.ObjectivesThe project's specific objectives include:(1) Develop and validate sensitive and species-specific qPCR procedures for quantifying M. hapla in soil;(2) Quantify the relationship between M. hapla population densities and crop damage/yield in potato;(3) Evaluate the susceptibility of commercial potato varieties to M. hapla for defining risk thresholds;(4) Disseminate research findings to growers and industry stakeholders to facilitate enhanced awareness of soilborne pathogens and options for improving profitability, productivity and sustainability of the U.S. potato industry; and(5) Provide graduate level training to PD Gorny in applied plant pathology and nematology with a focus in research and extension as a platform for achieving her career goals.

Project Methods
Objective 1: Development of Species-Specific qPCR test for Detection of Meloidogyne haplaSequences of the 16D10 effector gene from economically important Meloidogyne spp. are available in the GenBank database of NCBI. The 16D10 effector gene is thought to encode a secreted signaling molecule that is essential in RKN feeding site establishment (Huang et al., 2006). Sequences will be retrieved and aligned using MUSCLE (Edgar, 2004) and polymorphic regions identified. Primers and probe sets will be designed to these regions and specificity tested by assaying the primer and probe combinations against other plant-parasitic nematodes and commonly encountered soil microorganisms. The sensitivity of the test will be determined by serial dilutions of M. hapla DNA. The lowest sensitivity will be reported as the concentration of DNA that produces a detectible fluorescence signal when compared to the no-template control. Standard curves will be developed and fluorescence measurements back-calculated to quantify nematode numbers in the original sample.Objective 2: Quantification of relationship between M. hapla densities and crop damagea. On-Farm TrialsThree commercial potato fields in NY with high populations of M. hapla will be intensively sampled, prior to planting (May) and at harvest (September) along a 10×10 point grid. Soil samples will be homogenized and approximately 200 g of soil air dried for DNA extraction using the method developed by PD Gorny described above. Another sub-sample (200 g) will be used for manual nematode extraction and quantification using a modified Whitehead try technique (Whitehead and Hemming, 1965). A final sub-sample of 200 g of soil will used for a greenhouse bioassay. At harvest, the same sample processing protocol will be repeated. Additionally, plants along a 1 m row at each sampling location will be removed, and measurements of yield, crop damage, root galling severity, fresh and dry weight of roots, tuber yield and set, tuber diameter, and tuber damage collected.Population counts of RKN through manual counting and DNA analysis will be correlated to tuber damage within foci of varying densities using receiver operating characteristic (ROC) curve analysis (Hanley and McNeil, 1982). ROC curves plots the rate of true positives to the rate of true negatives, and the area under the curve by trapezoidal integration to determine the efficiency trade-offs by which DNA levels predict damage or yield reductions (Hanley and McNeil, 1982). Paired t-tests and other statistics will be performed to examine differences in M. hapla distribution and density were significantly different between planting and harvest.b. Replicated Field TrialPotato seed pieces of two commonly grown fresh market varieties will be planted into biodegradable pots and maintained in the greenhouse until emergence. Soil will be inoculated by delivering the appropriate amount of quantified inoculum to four small holes made around the base of the plant. Five population densities (125, 250, 500, and 1,000 M. hapla J2s per plant and a sterile water control) will be included in the study. Inoculated plants will be transplanted into a field at Cornell University's H.C. Thompson Vegetable Research Farm in Freeville, NY. Each population level will be replicated over six plots, and each plot will be five tubers in a single row. Weeds, insect pests and foliar disease will be managed with standard agronomic practices. In early September, plants will be desiccated and plots harvested by hand. Data on total plot yield, average tuber length, and disease severity will be collected. The final population density in each plot will be determined through DNA quantification. The relationship between the initial and final population densities (Pf/Pi), total yield, and crop damage will be explored using regression analysis conducted by building linear and non-linear models with the R function 'glm' in RStudio and summarizing the relationship between predictor (initial population) and response variables (yield, tuber damage, final population, etc.) with model fit statistics (e.g. R2, SEE-y, and CV (%)). The economic threshold for M. hapla will be calculated by determining the lowest population density resulting in significant yield reduction.Objective 3: Quantify the susceptibility of commercial potato varieties to M. haplaGreenhouse trials will be conducted to quantify the susceptibility of 11 potato varieties to M. hapla and identify damage thresholds. Seed pieces will be placed in pasteurized topsoil in 1.5 L plastic pots and maintained in the greenhouse. When plants emerge, plants will be inoculated with 500 and 1,500 J2s per pot and a sterile water non-inoculated control. Five replicates will be used for each variety × nematode density combination. Eight weeks after inoculation (sufficient time for one generation), plants will be harvested and total yield, tuber damage, number of tubers, and fresh and dry weight of roots recorded. The relationship between Pf/Pi, total yield, and crop damage will be explored using regression analysis. Varietal responses to damage will be investigated using generalized linear modeling in RStudio by generating a linear model with predictor (potato variety and initial population level) and response variables (yield at harvest, tuber damage, root mass weights, final population level) using the R function 'glm'. Relationships between predictor and response variables will be explored using regression analyses and mean separation between treatments calculated (R function 'LSD.test').Objective 4: Dissemination of research findings to growers and industry stakeholdersEfforts for formally disseminating research findings will be done through engagement of growers with experiential learning activities. PD Gorny will utilize programming and networks maintained by CCE to maximize impact and scope of dissemination. Results will be presented orally at CCE events, field days, and expos. Information will be published and distributed within written materials provided to growers, including extension factsheets and news bulletins within Cornell's VegEdge newsletter. This information will also be suitable for delivery through eXtension (https://extension.org). Informal educational efforts for disseminating research findings will consist of on-farm consultation with participating growers.Objective 5: Graduate training for the Project DirectorThis training will enhance PD Gorny's competence as a researcher and extension specialist fulfilling the AFRI ELI Fellowship Grant Program goal to "prepare the next generation of scientists through doctoral and post-doctoral fellowships."Evaluation PlanEvaluation of the training/career development, mentoring, approach and dissemination plans will be formative and rely upon feedback from PD Gorny's major advisor (Co-PM Pethybridge) and committee members (Co-PM Pethybridge, Co-PM Wang, Dr. Stephen Reiners, and Dr. Paul Esker). Annual self-evaluation forms administered by the Cornell University Graduate School will be completed and reviewed. Progress will be measured by reaching the appropriate milestones, including coursework (completed), presentation and publication of research in academic and extension venues, admission to candidacy exam (completed), mentoring of undergraduates, and thesis preparation. Results will be submitted to peer reviewed journals (one manuscript per Objectives 1-3). Further, feedback will be sought from potato growers and attendees at extension presentations with CCE. Summative evaluations will be designed to assist in training (Objective 5). The use of formative and summative evaluation strategies are foundational in the extension training of PD Gorny, and will be included in project reports.

Progress 04/01/18 to 03/31/20

Outputs
Target Audience:The target audience of this integrated project was agricultural stakeholders, including potato producers, industry leaders, and crop consultants, as well as academic affiliates, including university cooperative extension personnel, faculty, and agricultural research scientists. The target audiences were reached through products and outputs tailored to the specific group. Efforts to reach growers in New York State participating in this research focused in on-farm consultations, personalized discussions and summary reports of research findings. Efforts to reach broader producer groups, crop consultants, and industry leaders included presentations and interactions at extension and commodity meetings. Efforts to reach academics and agricultural research scientists focused in Project Director Gorny's participation in academic conferences and submission of research manuscripts for peer-review and publication in academic journals. Research manuscripts included one detailing the development of a species-specific quantitative PCR assay for detection and quantification of Meloidogyne hapla (Objective 1), and another detailing results of spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations within sampled commercial potato fields. An additional education manuscript was prepared and submitted for review to Plant Health Instructor. This manuscript details a method for rearing M. hapla hydroponically for visualization of root-knot nematode second-stage juveniles by students in plant pathology courses. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The research activities conducted through this integrated project provided for the continual training in agricultural research and extension for PD Gorny by facilitating development of field research trials and interaction with potato producers in NY. On-farm trials were conducted to address Objective 2 and results disseminated to stakeholders within Objective 4. PD Gorny discussed nematode management issues with producers in NY, leading to an enhanced understanding of potato production practices and economic drivers of disease management, and the producers' better understanding of nematode biology and management options. Within the project, PD Gorny compiled written reports for the participating producers tailored to findings from each farm. Additionally, she presented at extension events attended by potato producers from across NY and the Northeastern United States. This work resulted in PD Gorny's enhanced ability to translate scientific results for non-academic stakeholders. Within the project, PD Gorny also took advantage of professional development opportunities through participation in academic conferences, mainly participation in the World Potato Congress in Cusco, Peru and the International Congress of Plant Pathology in Boston, MA. At these conferences, she had the opportunity to present her research in a formal setting, and also expand her professional network by interacting with national and international colleagues working in nematology, potato research, and broader plant pathology topics. The training and professional experiences obtained during this project were integral in preparing PD Gorny for successfully securing a position as Assistant Professor of Plant Nematology at North Carolina State University, thereby affording PD Gorny the opportunity to advance her interests and achieve her career goals in nematology research and extension. How have the results been disseminated to communities of interest?The findings from this project changed the state of knowledge in the areas of molecular detection of pathogens, spatial analysis of soilborne pathogen populations, and crop loss risk prediction. This change in knowledge benefits agricultural scientists, extension personnel, and crop consultants. These findings may also help to accomplish change in practices by reducing prophylactic nematicide usage by potato producers. This change in action will benefit producers, industry stakeholders, and rural agricultural communities through advancing methods to maximize economic returns and minimizing negative environmental impacts. Participating potato producers received a detailed written summary of the findings from on-farm trials, including information on the nematode species present and the populations quantified. Results were discussed in person with the producers individually, and any questions or concerns addressed. An oral presentation was delivered at the New York Potato School in February 2019, in Waterloo, NY. This two-day event is the premiere potato extension meeting for the state and was attended by approximately 75 producers and extension personnel. The presentation discussed the use of nematicides for cost effective nematode control in potato fields in context of the results found in the on-farm sampling (Objective 2a). The results of the greenhouse trial assessing the differential response of potato cultivars to M. hapla (Objective 3) were presented at two academic conferences, the World Potato Congress and the International Congress of Plant Pathology. These two conferences were attended by academics in different specialty areas, ensuring the results were disseminated to a broad range of researchers. Further, a invited seminar presentation was delivered by PD Gorny to the Department of Plant Pathology and Environmental Microbiology at the Pennsylvania State University (14 April 2019; "Supporting the improved management of the Northern root-knot nematode Meloidogyne hapla, in potato in New York State"). These conferences and seminar were attended by academics in plant pathology and potato research, ensuring the findings from this project were disseminated to a broad range of researchers. An academic paper detailing the development of the species-specific quantitative PCR assay for detection and quantification of M. hapla in soil was prepared for publication and submitted to the academic journal Plant Disease for review. This manuscript was accepted and is available for other researchers through a "First Look" option electronically (https://apsjournals.apsnet.org/doi/10. 1094/PDIS-09-18-1539-RE). An academic paper relating the findings of associations between initial population densities of M. hapla to potato crop damage and yield loss is in preparation, with anticipated submission to the journal Plant Health Progress. An additional academic paper detailing results of the spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations within the sampled commercial potato fields is in preparation, with anticipated submission to the Journal of Nematology. An educational manuscript describing the development and use of a hydroponics system for rearing of M. hapla J2s was prepared and submitted for review to the education-focused journal The Plant Health Instructor. This article will be useful to educators at high-school and college levels for preparing classroom materials and developing laboratory exercises directed at understanding RKN and other sedentary endoparasitic plant-parasitic nematode biology and ecology (Objective 4). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project investigated the association between initial population densities (Pi) of the Northern root-knot nematode, Meloidogyne hapla, and tuber damage and yield reductions in potato crops in NY. This project established a framework for a DNA-based soil test to quantify M. hapla Pi in the soil, thus providing an alternative to labor intensive and challenging standard methods of extracting and quantifying nematodes. Although M. hapla is frequently considered ubiquitous in agricultural fields, the economic threshold for informing when pre-plant nematicide applications are needed for control is not well understood. Producers frequently make prophylactic nematicide applications, potentially resulting in "false positive decisions", in which a nematicide is applied when true populations in the soil are below a level leading to economic loss. This may lead to increased production costs by increasing inputs, maintaining selection pressure on pathogen populations in the soil, and may have deleterious environmental effects. The major impacts of this project are two-fold: (1) this work established important components of a DNA-based soil test for detection and quantification of M. hapla Pi in soil; and (2) this project could find no significant association between M. hapla Pi and tuber damage or yield loss, indicating that prophylactic nematicides may not be needed for control in potato. An expanded discussion of specific accomplishments within each of the project Objectives are outlined within previous annual reports. A summary is given here: 1. Objective (1) was to develop a sensitive and species-specific quantitative PCR (qPCR) procedure to detect and quantify M. hapla directly from soil. A species-specific qPCR assay for M. hapla targeting the 16D10 effector gene was developed and validated to accomplish this objective. This work resulted in a change in knowledge by exploring the hypothesis that nematode effector genes may be used as species-specific targets for molecular quantification. 2. Objective (2) was to quantify the relationship between M. hapla population densities prior to planting and crop damage/yield loss in potato. Under this objective, an on-farm trial and a replicated field trial were conducted to investigate this relationship. Within the on-farm trial, no significant association was found between the Pi measured through either manual extraction or DNA quantification, and potato crop damage/yield loss. These results suggest cultivar assessed may be tolerant to M. hapla and the economic threshold may be higher than previously regarded (at approximately 100 M. hapla J2 per 100 g soil; Barker & Olthof 1976). This economic threshold has been a standard measure for indicating if a pre-plant nematicide is warranted to mitigate crop loss and damage. This finding may result in a change in action by potentially negating the need for pre-plant nematicides in many cases for control of M. hapla in NY in this cultivar due to tolerance. Within the replicated field trial, the effect of M. hapla and the lesion nematode, Pratylenchus penetrans, were assessed on two popular potato cultivars, Eva and Lamoka. Neither M. hapla Pi nor P. penetrans Pi had a significant effect on total yield. Analogous to the findings of the on-farm trial, these results suggest these cultivars may have tolerance to M. hapla and P. penetrans, which may facilitate preferential selection of these cultivars under high disease pressure. These results also suggest that the previously used economic thresholds of 100 M. hapla J2 and 200-600 P. penetrans nematodes per 100 g of soil (Barker & Olthof 1976) are not accurate for potato cultivars currently preferred by NY producers. Because no significant reductions in total yield or increases in crop damage were observed with increasing M. hapla or P. penetrans Pi, a reduction in usage of pre-plant nematicides may be appropriate for potato producers in NY. This change in action could lead to a reduction in input costs and increased environmental sustainability with no significant impact on yield. An additional research topic undertaken was the spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations present within the fields. Little is known of the spatial patterns and spatiotemporal dynamics of populations of these nematodes in commercial potato fields in NY, yet this information can be useful in developing enhanced sampling protocols and aids in the cost-benefit analysis to evaluate the potential of site-specific nematicide application. Using population count data gathered from on-farm trials collected prior to this project, spatial patterns of M. hapla and Pratylenchus spp. were quantified through geostatistical methods of semivariogram analysis and ordinary kriging, and Spatial Analysis by Distance IndicEs (SADIE). Semivariogram analysis and ordinary kriging indicated Pi to be spatially dependent over an average range of 110 m for M. hapla and 147 m for Pratylenchus spp. SADIE indicated populations of Pratylenchus spp. to be significantly aggregated in nearly all fields (10 of 12 samplings, Ia = 1.367 to 2.113). M. hapla populations were aggregated at only a few instances (3 of 12 samplings, Ia = 1.318 to 1.738). Spatiotemporal analysis using the Association Function of SADIE indicated a strong and significant association between Pi and Pf of M. hapla and Pratylenchus spp. within fields. 3. Objective (3) was to evaluate the susceptibility of commercial potato cultivars commonly grown in NY to M. hapla for defining risk thresholds. A greenhouse trial was conducted to evaluate the susceptibility of eleven different potato cultivars to M. hapla. It was found that cultivar had a significant effect on reproductive factor, final population, and root galling severity. Additionally, M. hapla Pi had a significant effect on root galling severity, Pf in the soil, and Pf/Pi. However, Pi did not have a significant influence on total yield. This work added to scientific understanding of cultivar response to M. hapla, resulting in a change in knowledge. This information is important for producers when making cultivar selections, and may also be useful to potato breeders for breeding projects for tolerance and resistance to root-knot nematode in potato. Furthermore, from this work a method for hydroponically rearing M. hapla J2s for inoculating plants was developed and submitted for review to Plant Health Instructor. 4. Objective (4) was to disseminate the research findings to potato producers and industry stakeholders to facilitate enhanced awareness of soilborne pathogens, nematode management, and options for improving profitability. Research findings from Objectives (1), (2), and (3) were disseminated to stakeholder groups through an extension presentation (New York Potato School, in Waterloo, NY, 19 February 2019) and written materials (research reports for participating producers). 5. Objective (5) was to provide graduate level training to the project director in applied plant pathology and nematology. Within this project, Project Director (PD) Gorny has gained experience talking with agricultural scientists in NY and translating the research conducted within this project to different target audiences, including growers, Cornell Cooperative Extension personnel, and academic faulty and scientists. PD Gorny has presented to academic audiences through a poster presentation at the World Potato Congress in Cusco, Peru, a poster presentation at the International Congress of Plant Pathology, and an invited oral presentation at Pennsylvania State University. PD Gorny also prepared and defended her doctoral dissertation in July 2019. PD Gorny will join North Carolina State University (Raleigh, NC) on 20 August as an Assistant Professor of Plant Nematology with responsibilities in research and extension in major commodities of North Carolina. REF: Barker & Olthof. 1976. Annu. Rev. Phytopathol. 14:327-353.

Publications

• Type: Theses/Dissertations Status: Submitted Year Published: 2019 Citation: Gorny, A. M. 2019. Quantifying risk for the Northern root-knot nematode, Meloidogyne hapla, in potato in New York State. (Doctoral dissertation). Cornell University, Ithaca, New York, USA.
• Type: Journal Articles Status: Other Year Published: 2019 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2019. Spatial and spatiotemporal analysis of Meloidogyne hapla and Pratylenchus spp. populations in commercial potato fields in New York. Journal of Nematology [In preparation].
• Type: Journal Articles Status: Other Year Published: 2019 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2019. Rethinking the economic threshold for the Northern root-knot nematode (Meloidogyne hapla) in New York potato production. Plant Health Progress [In preparation].

Progress 04/01/18 to 07/22/19

Outputs
Target Audience:The target audience of this integrated project was agricultural stakeholders, including potato producers, industry leaders, and crop consultants, as well as academic affiliates, including university cooperative extension personnel, faculty, and agricultural research scientists. The target audiences were reached through products and outputs tailored to the specific group. Efforts to reach growers in New York State participating in this research focused in on-farm consultations, personalized discussions and summary reports of research findings. Efforts to reach broader producer groups, crop consultants, and industry leaders included presentations and interactions at extension and commodity meetings. Efforts to reach academics and agricultural research scientists focused in Project Director Gorny's participation in academic conferences and submission of research manuscripts for peer-review and publication in academic journals. Research manuscripts included one detailing the development of a species-specific quantitative PCR assay for detection and quantification of Meloidogyne hapla (Objective 1), and another detailing results of spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations within sampled commercial potato fields. An additional education manuscript was prepared and submitted for review to Plant Health Instructor. This manuscript details a method for rearing M. hapla hydroponically for visualization of root-knot nematode second-stage juveniles by students in plant pathology courses. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The research activities conducted through this integrated project provided for the continual training in agricultural research and extension for PD Gorny by facilitating development of field research trials and interaction with potato producers in NY. On-farm trials were conducted to address Objective 2 and results disseminated to stakeholders within Objective 4. PD Gorny discussed nematode management issues with producers in NY, leading to an enhanced understanding of potato production practices and economic drivers of disease management, and the producers' better understanding of nematode biology and management options. Within the project, PD Gorny compiled written reports for the participating producers tailored to findings from each farm. Additionally, she presented at extension events attended by potato producers from across NY and the Northeastern United States. This work resulted in PD Gorny's enhanced ability to translate scientific results for non-academic stakeholders. Within the project, PD Gorny also took advantage of professional development opportunities through participation in academic conferences, mainly participation in the World Potato Congress in Cusco, Peru and the International Congress of Plant Pathology in Boston, MA. At these conferences, she had the opportunity to present her research in a formal setting, and also expand her professional network by interacting with national and international colleagues working in nematology, potato research, and broader plant pathology topics. The training and professional experiences obtained during this project were integral in preparing PD Gorny for successfully securing a position as Assistant Professor of Plant Nematology at North Carolina State University, thereby affording PD Gorny the opportunity to advance her interests and achieve her career goals in nematology research and extension. How have the results been disseminated to communities of interest?The findings from this project changed the state of knowledge in the areas of molecular detection of pathogens, spatial analysis of soilborne pathogen populations, and crop loss risk prediction. This change in knowledge benefits agricultural scientists, extension personnel, and crop consultants. These findings may also help to accomplish change in practices by reducing prophylactic nematicide usage by potato producers. This change in action will benefit producers, industry stakeholders, and rural agricultural communities through advancing methods to maximize economic returns and minimizing negative environmental impacts. Participating potato producers received a detailed written summary of the findings from on-farm trials, including information on the nematode species present and the populations quantified. Results were discussed in person with the producers individually, and any questions or concerns addressed. An oral presentation was delivered at the New York Potato School in February 2019, in Waterloo, NY. This two-day event is the premiere potato extension meeting for the state and was attended by approximately 75 producers and extension personnel. The presentation discussed the use of nematicides for cost effective nematode control in potato fields in context of the results found in the on-farm sampling (Objective 2a). The results of the greenhouse trial assessing the differential response of potato cultivars to M. hapla (Objective 3) were presented at two academic conferences, the World Potato Congress and the International Congress of Plant Pathology. These two conferences were attended by academics in different specialty areas, ensuring the results were disseminated to a broad range of researchers. Further, a invited seminar presentation was delivered by PD Gorny to the Department of Plant Pathology and Environmental Microbiology at the Pennsylvania State University (14 April 2019; "Supporting the improved management of the Northern root-knot nematode Meloidogyne hapla, in potato in New York State"). These conferences and seminar were attended by academics in plant pathology and potato research, ensuring the findings from this project were disseminated to a broad range of researchers. An academic paper detailing the development of the species-specific quantitative PCR assay for detection and quantification of M. hapla in soil was prepared for publication and submitted to the academic journal Plant Disease for review. This manuscript was accepted and is available for other researchers through a "First Look" option electronically (https://apsjournals.apsnet.org/doi/10. 1094/PDIS-09-18-1539-RE). An academic paper relating the findings of associations between initial population densities of M. hapla to potato crop damage and yield loss is in preparation, with anticipated submission to the journal Plant Health Progress. An additional academic paper detailing results of the spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations within the sampled commercial potato fields is in preparation, with anticipated submission to the Journal of Nematology. An educational manuscript describing the development and use of a hydroponics system for rearing of M. hapla J2s was prepared and submitted for review to the education-focused journal The Plant Health Instructor. This article will be useful to educators at high-school and college levels for preparing classroom materials and developing laboratory exercises directed at understanding RKN and other sedentary endoparasitic plant-parasitic nematode biology and ecology (Objective 4). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project investigated the association between initial population densities (Pi) of the Northern root-knot nematode, Meloidogyne hapla, and tuber damage and yield reductions in potato crops in NY. This project established a framework for a DNA-based soil test to quantify M. hapla Pi in the soil, thus providing an alternative to labor intensive and challenging standard methods of extracting and quantifying nematodes. Although M. hapla is frequently considered ubiquitous in agricultural fields, the economic threshold for informing when pre-plant nematicide applications are needed for control is not well understood. Producers frequently make prophylactic nematicide applications, potentially resulting in "false positive decisions", in which a nematicide is applied when true populations in the soil are below a level leading to economic loss. This may lead to increased production costs by increasing inputs, maintaining selection pressure on pathogen populations in the soil, and may have deleterious environmental effects. The major impacts of this project are two-fold: (1) this work established important components of a DNA-based soil test for detection and quantification of M. hapla Pi in soil; and (2) this project could find no significant association between M. hapla Pi and tuber damage or yield loss, indicating that prophylactic nematicides may not be needed for control in potato. An expanded discussion of specific accomplishments within each of the project Objectives are outlined within previous annual reports. A summary is given here: 1. Objective (1) was to develop a sensitive and species-specific quantitative PCR (qPCR) procedure to detect and quantify M. hapla directly from soil. A species-specific qPCR assay for M. hapla targeting the 16D10 effector gene was developed and validated to accomplish this objective. This work resulted in a change in knowledge by exploring the hypothesis that nematode effector genes may be used as species-specific targets for molecular quantification. 2. Objective (2) was to quantify the relationship between M. hapla population densities prior to planting and crop damage/yield loss in potato. Under this objective, an on-farm trial and a replicated field trial were conducted to investigate this relationship. Within the on-farm trial, no significant association was found between the Pi measured through either manual extraction or DNA quantification, and potato crop damage/yield loss. These results suggest cultivar assessed may be tolerant to M. hapla and the economic threshold may be higher than previously regarded (at approximately 100 M. hapla J2 per 100 g soil; Barker & Olthof 1976). This economic threshold has been a standard measure for indicating if a pre-plant nematicide is warranted to mitigate crop loss and damage. This finding may result in a change in action by potentially negating the need for pre-plant nematicides in many cases for control of M. hapla in NY in this cultivar due to tolerance. Within the replicated field trial, the effect of M. hapla and the lesion nematode, Pratylenchus penetrans, were assessed on two popular potato cultivars, Eva and Lamoka. Neither M. hapla Pi nor P. penetrans Pi had a significant effect on total yield. Analogous to the findings of the on-farm trial, these results suggest these cultivars may have tolerance to M. hapla and P. penetrans, which may facilitate preferential selection of these cultivars under high disease pressure. These results also suggest that the previously used economic thresholds of 100 M. hapla J2 and 200-600 P. penetrans nematodes per 100 g of soil (Barker & Olthof 1976) are not accurate for potato cultivars currently preferred by NY producers. Because no significant reductions in total yield or increases in crop damage were observed with increasing M. hapla or P. penetrans Pi, a reduction in usage of pre-plant nematicides may be appropriate for potato producers in NY. This change in action could lead to a reduction in input costs and increased environmental sustainability with no significant impact on yield. An additional research topic undertaken was the spatial and spatiotemporal analysis of M. hapla and Pratylenchus spp. populations present within the fields. Little is known of the spatial patterns and spatiotemporal dynamics of populations of these nematodes in commercial potato fields in NY, yet this information can be useful in developing enhanced sampling protocols and aids in the cost-benefit analysis to evaluate the potential of site-specific nematicide application. Using population count data gathered from on-farm trials collected prior to this project, spatial patterns of M. hapla and Pratylenchus spp. were quantified through geostatistical methods of semivariogram analysis and ordinary kriging, and Spatial Analysis by Distance IndicEs (SADIE). Semivariogram analysis and ordinary kriging indicated Pi to be spatially dependent over an average range of 110 m for M. hapla and 147 m for Pratylenchus spp. SADIE indicated populations of Pratylenchus spp. to be significantly aggregated in nearly all fields (10 of 12 samplings, Ia = 1.367 to 2.113). M. hapla populations were aggregated at only a few instances (3 of 12 samplings, Ia = 1.318 to 1.738). Spatiotemporal analysis using the Association Function of SADIE indicated a strong and significant association between Pi and Pf of M. hapla and Pratylenchus spp. within fields. 3. Objective (3) was to evaluate the susceptibility of commercial potato cultivars commonly grown in NY to M. hapla for defining risk thresholds. A greenhouse trial was conducted to evaluate the susceptibility of eleven different potato cultivars to M. hapla. It was found that cultivar had a significant effect on reproductive factor, final population, and root galling severity. Additionally, M. hapla Pi had a significant effect on root galling severity, Pf in the soil, and Pf/Pi. However, Pi did not have a significant influence on total yield. This work added to scientific understanding of cultivar response to M. hapla, resulting in a change in knowledge. This information is important for producers when making cultivar selections, and may also be useful to potato breeders for breeding projects for tolerance and resistance to root-knot nematode in potato. Furthermore, from this work a method for hydroponically rearing M. hapla J2s for inoculating plants was developed and submitted for review to Plant Health Instructor. 4. Objective (4) was to disseminate the research findings to potato producers and industry stakeholders to facilitate enhanced awareness of soilborne pathogens, nematode management, and options for improving profitability. Research findings from Objectives (1), (2), and (3) were disseminated to stakeholder groups through an extension presentation (New York Potato School, in Waterloo, NY, 19 February 2019) and written materials (research reports for participating producers). 5. Objective (5) was to provide graduate level training to the project director in applied plant pathology and nematology. Within this project, Project Director (PD) Gorny has gained experience talking with agricultural scientists in NY and translating the research conducted within this project to different target audiences, including growers, Cornell Cooperative Extension personnel, and academic faulty and scientists. PD Gorny has presented to academic audiences through a poster presentation at the World Potato Congress in Cusco, Peru, a poster presentation at the International Congress of Plant Pathology, and an invited oral presentation at Pennsylvania State University. PD Gorny also prepared and defended her doctoral dissertation in July 2019. PD Gorny will join North Carolina State University (Raleigh, NC) on 20 August as an Assistant Professor of Plant Nematology with responsibilities in research and extension in major commodities of North Carolina. REF: Barker & Olthof. 1976. Annu. Rev. Phytopathol. 14:327-353.

Publications

• Type: Theses/Dissertations Status: Submitted Year Published: 2019 Citation: Gorny, A. M. 2019. Quantifying risk for the Northern root-knot nematode, Meloidogyne hapla, in potato in New York State. (Doctoral dissertation). Cornell University, Ithaca, New York, USA.
• Type: Journal Articles Status: Other Year Published: 2019 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2019. Spatial and spatiotemporal analysis of Meloidogyne hapla and Pratylenchus spp. populations in commercial potato fields in New York. Journal of Nematology [In preparation].
• Type: Journal Articles Status: Other Year Published: 2019 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2019. Rethinking the economic threshold for the Northern root-knot nematode (Meloidogyne hapla) in New York potato production. Plant Health Progress [In preparation].

Progress 04/01/18 to 03/31/19

Outputs
Target Audience:The target audience of this integrated research project includes potato producers, industry stakeholders, crop consultants, university cooperative extension personnel, academic faculty, and agricultural research scientists. Ongoing outreach to the target audiences has been achieved through avenues tailored to the specific group. Participating producers in New York State have been engaged in on-farm consultations and personalized discussions of the research findings. Producers, industry leaders, and extension personnel are being reached through extension and commodity meetings, listed in this report as Products herein. Academic faculty and researchers have been reached through Project Director Gorny's participation in academic conferences and outputs listed in the Products section. An academic paper detailing the development of a species-specific quantitative PCR assay for detection and quantification of Meloidogyne hapla (Objective 1) was accepted for publication by the journal Plant Disease and is available on First Look for other researchers to access. Additionally, an academic manuscript detailing a method for rearing M. hapla hydroponically was prepared and submitted for review to Plant Health Instructor, where once published, educators and researchers may access to use the method in the laboratory and classroom. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project has provided for the continued training in agricultural extension for PD Gorny through interaction with New York potato producers for establishment and maintenance of the on-farm trial, leading to a better understanding of the production practices and economic drivers of disease management for New York potato producers. The project has also provided opportunities to prepare written reports for the participating producers and present at extension events attended by potato producers from across New York and the Northeastern United States, resulting in PD Gorny's enhanced ability to translate scientific results for non-academic stakeholders. The project has also provided professional development through PD Gorny's participation in the World Potato Congress in Cusco, Peru, the International Congress of Plant Pathology in Boston, MA, thereby expanding her professional network and presenting her current research. The training and professional experiences obtained during this project were integral in preparing PD Gorny for successfully securing a position as Assistant Professor of Plant Nematology at North Carolina State University, thereby affording PD Gorny the opportunity to advance her interests and achieve her career goals in nematology research and extension. ? How have the results been disseminated to communities of interest?A summary of the nematode populations quantified from on-farm soil sampling was prepared for the participating potato producers. The results were discussed with the producers individually, and questions from the producers were addressed. An oral presentation was given at the New York Potato School in February 2019, in Waterloo, NY. This two-day event is the premiere potato extension meeting for the state and was attended by approximately 75 producers and extension personnel. This presentation discussed the use of nematicides for cost effective nematode control in potato fields in context of the results found in the on-farm sampling (Objective 2a). An academic paper detailing the development of the species-specific quantitative PCR assay for detection and quantification of M. hapla in soil was prepared for publication and submitted to the academic journal Plant Disease for review. This manuscript was accepted and is available for other researchers through a "First Look" option electronically (https://apsjournals.apsnet.org/doi/10. 1094/PDIS-09-18-1539-RE). An additional educational manuscript describing the development and use of a hydroponics system for rearing of M. hapla J2s was prepared and submitted for review to the education-focused journal The Plant Health Instructor. This article will be useful to educators at high-school and college levels for preparing classroom materials and developing laboratory exercises directed at understanding RKN and other sedentary endoparasitic plant-parasitic nematode biology and ecology (Objective 4). The results of the greenhouse trial assessing the differential response of potato cultivars to M. hapla (Objective 3) were presented at two academic conferences, the World Potato Congress and the International Congress of Plant Pathology. Additionally, an invited seminar presentation was given to the Department of Plant Pathology and Environmental Microbiology at Peensylvania State University (14 April 2019; "Supporting the improved management of the Northern root-knot nematode, Meloidogyne hapla, in potato in New York State"). These two conferences and seminar were attended by academics in different specialty areas, ensuring the results were disseminated to a broad range of researchers. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, data gathered from the on-farm trials will be analyzed using spatial regression modeling to determine if spatial autocorrelation inherently present in the dataset may be influencing results (Objective 2a). Spatial distribution of M. hapla and P. penetrans over the sampled area will be explored using geostatistics, and indexes of aggregation calculated to determine the degree of spatial dependence. This knowledge will help inform the number of soil samples effectively required to accurately estimate true populations within the field. PD Gorny will continue to disseminate results of the work to producers and stakeholder groups through Cornell Cooperative Extension events, and academic groups through participation in academic conferences and preparation of research manuscripts. PD Gorny is also in progress of preparing her doctoral dissertation and it will be completed within the timeframe of this fellowship. PD Gorny's doctoral dissertation will include the research objectives and findings outlined within this project.

Impacts
What was accomplished under these goals? 1. A species-specific qPCR assay for M. hapla was developed. Sequences available of the 16D10 root-knot nematode effector gene were downloaded from NCBI GenBank (Acc. No. DQ841121; DQ841122; DQ841123; and DQ087264), aligned, and polymorphic regions identified for design of qPCR primers in M. hapla. One set referred to as Mha17F/R was identified for further study and its specificity tested using conventional and qPCR by assaying 5 isolates of M. hapla and 13 isolates of non-target plant parasitic nematode species. Mha17F/R was species-specific, and only produced positive amplification in the M. hapla isolates. The sensitivity of the primers was determined through qPCR by assaying serial dilutions of M. hapla DNA between 790 and 0.079 pg/µL. The primers amplified the target even at the highest dilution. The work under this objective was summarized in a manuscript that was accepted for publication to the journal Plant Disease. 2.An on-farm trial (a) and replicated field trials (b) were conducted to investigate the relationship between M. hapla population densities and crop loss in potato. (a) A commercial potato field in western NY planted to cv. Envol was selected for study in collaboration with potato producers. Three gridded plots were established in the field, each consisting of 10 consecutive rows by 10 sampling points within each row. Initial populations densities (Pi) of M. hapla were estimated in May by collecting 1 kg of soil at each grid location along a 1 m transect. A subsample of this soil underwent manual nematode quantification of M. hapla second-stage juveniles (J2s). A second subsample underwent DNA extraction using the method described by Gorny et al. (2018) and quantification of M. hapla by qPCR. Final population densities (Pf) of M. hapla were estimated in September by collecting 1 kg of soil at each grid location along a 1 m transect. A subsample of this soil underwent manual nematode quantification. At this sampling, plants within the same transect were removed, and data on yield (kg), number of tubers, tuber diameter (mm), and disease severity scores were collected. M. hapla Pi and Pf were highly variable within the three gridded areas. There was a significant positive association between M. hapla Pi measured through manual counting and M. hapla Pi estimated through qPCR, indicating the DNA extraction method was a robust tool. No significant association was found between the Pi measured through either quantification method and yield components. These results suggest cv. Envol may be tolerant to M. hapla and/or the threshold may be higher than previously regarded (approx. 100 M. hapla J2/100 g soil; Barker and Olthof 1976). This threshold has been a standard for indicating if a pre-plant nematicide is warranted to mitigate crop loss. This finding potentially negates the need for pre-plant nematicides in many cases for control of M. hapla in NY in this cultivar. (b) Replicated field trials were established at the H.C. Thompson Vegetable Research Farm in Freeville, NY. Potato seed pieces of the popular cvs. Eva and Lamoka were placed into biodegradable peat pots filled with pasteurized soil and maintained in the greenhouse until emergence, after which plants were inoculated with one of three M. hapla Pi (250 and 500 J2s/pot, plus a non-inoculated control). Three Pi of the root-lesion nematode, Pratylenchus penetrans (500 and 1,000 nematodes/pot, plus a non-inoculated control) were also included in the trials for exploration of potential synergistic effects. Each Pi was replicated over five plots, with each plot containing five plants. In August, the plots were vine killed and data collected on total yield (kg), average tuber length (mm), and disease severity within each plot. Pf for each plot was determined by collecting a soil sample and manually quantifying nematodes. Pi of neither species had a significant effect on total yield. Both M. hapla Pi and P. penetrans Pi had a significant effect on Pf in 2017. M. hapla Pi had a significant effect on tuber diameter in 2018, yet the mean separations were modest and likely do not represent economically significant differences. Analogous to the findings of Obj. 2a, these results suggest these cultivars may have tolerance to infection by M. hapla and P. penetrans, which may facilitate selection of these cultivars under high disease pressure. These results also suggest the previously used thresholds for potato of 100 M. hapla J2s/100 g of soil and 200-600 P. penetrans/100 g of soil (Barker and Olthof 1976) are not accurate for potato cultivars currently grown. Because no significant reductions in total yield or increases in crop damage were observed with increasing M. hapla or P. penetrans Pi, a reduction in usage of pre-plant nematicides could lead to a reduction in input costs with no significant impact on yield, supporting economic and environmental sustainability in NY rural communities. 3.A greenhouse trial was conducted to evaluate the susceptibility of potato cultivars to M. hapla. Seed pieces of 11 cultivars (Adirondack Blue, Atlantic, Eva, Lamoka, Nordana, Norland, NY140, Reba, Snowden, Upstate, Waneta, and a tomato RKN-susceptible control cv. Rutgers) were planted into plastic pots filled with pasteurized soil and maintained in the greenhouse. Three weeks after emergence, plants were inoculated with one of three M. hapla Pi levels (500 or 1,000 J2s per pot, or non-inoculated control). Plants were grown for eight weeks, after which they were destructively harvested and data collected. The relationship between predictor variables (cultivar, Pi) and response variables (yield, tuber set, root mass weights, root galling severity, Pf in the soil measured from a soil sample collected at time of harvest, number of nematodes per fresh gram of root, and Pf/Pi) were explored using regression analysis and mean separation between treatments. Cultivar had a significant effect on Pf/Pi, Pf in the soil, and root galling severity. M. hapla Pi had a significant effect on root galling severity, Pf in the soil, and Pf/Pi. Norland had the lowest Pf in the soil, lowest number of nematodes per fresh gram of root, and lowest Pf/Pi among the cultivars tested. Norland also had the lowest average root mass weight of the cultivars tested, perhaps resulting in a reduced capacity to support high M. hapla populations. All cultivars tested had low root galling severity scores (<12%) at all Pi. Therefore, statistical differences seen here between cultivars may be of little practical importance. From this work, a method for hydroponically rearing M. hapla J2s was developed and submitted for review to Plant Health Instructor. 4. Research findings from Objs. 1, 2, and 3 were disseminated to stakeholder groups through an extension presentation (New York Potato School, in Waterloo, NY, 19 February 2019), written materials (research reports for participating producers), and academic presentations, facilitating enhanced awareness of soilborne pathogens, nematode management, and options for improving profitability. 5. PD Gorny is continuing her graduate training within the fields of applied plant pathology and nematology, and has gained experience talking with producers in NY and translating the research conducted within this project to different target audiences, including growers, Cooperative Extension personnel, and academic faulty. PD Gorny has presented to academic audiences through poster presentations at the World Potato Congress in Cusco, Peru and at the International Congress of Plant Pathology, and also an invited oral talk at Pennsylvania State University. PD Gorny was successful in obtaining a position as Asst. Professor of Plant Nematology at NC State University, with responsibilities in research and extension in major commodities of NC, following the completion of her graduate studies and this USDA NIFA ELI Fellowship. Barker, K. R. and Olthof, T. H. A. 1976. Annu. Rev. Phytopathol. 14:327-353

Publications

• Type: Journal Articles Status: Awaiting Publication Year Published: 2019 Citation: Gorny, A. M., Wang, X., Hay, F. S. and Pethybridge, S. J. 2018. Development of a species-specific PCR for detection and quantification of Meloidogyne hapla in soil using the 16D10 root-knot nematode effector gene. Plant Disease. DOI: 10.1094/PDIS-09-18-1539-RE. [In Press].
• Type: Journal Articles Status: Under Review Year Published: 2019 Citation: Gorny, A. M., Cousins, P., Johnston, D., and Pethybridge, S. J. 2019. Establishment and maintenance of a hydroponics system for rearing of the Northern root-knot nematode (Meloidogyne hapla) second-stage juveniles. Plant Health Instructor. [Submitted for review].
• Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2019. The effect of Vydate on plant-parasitic nematode populations in New York potato fields. New York Potato School, Waterloo, NY, USA. Attendees = 50 people. Duration = 30 min. February 20, 2019.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2018. Differential responses of potato cultivars to Meloidogyne hapla. (Abstr.) Phytopathology 108:S1.26. DOI: 10.1094/PHYTO-108-10-S1.26.
• Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Gorny, A. M., Hay, F. S., and Pethybridge, S. J. 2018. Reproductive fitness of Meloidogyne hapla on eleven potato cultivars. Pp 131 in: Proceedings of the 10th World Potato Congress - XXVIII ALAP 2018 Congress: Biodiversity, Food Security and Business. Instituto Nacional de Innovacion Agraria-INIA. Cusco, Peru.