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W1186: Genetic Variability in the Cyst and Root-Knot Nematodes

Duration:
October 01, 2003 to September 30, 2008
Administrative Advisor(s):
Donald Cooksey (CALB)
NIFA Reps:
Martin A Draper

Statement of Issue(s) and Justification:

The Need as Indicated by Stakeholders: Plant-parasitic nematodes cause an estimated 10-14% average annual yield loss among the world's major crops (Sasser and Freckman, 1987). Losses in United States major crops due to plant-parasitic nematodes are estimated to range from minimal in some localities to as high as 15% in other areas (Koenning et al., 1999; McSorley et al., 1987). Increasingly, scientific evidence and public awareness have heightened concerns about environment quality, food quality, and human health and safety relative to pest management in agricultural production. The need for alternative, integrated nematode management has been propelled by the actions triggered by the Montreal Protocol and the Food Quality Protection Act (FQPA) of the 1990s. Based on FQPA requirements, it is likely that several widely-used and efficacious nematicides will be unavailable in the future. For example, the nematicide 1,3-dichloropropene (Telone II) is a B2 carcinogen, and is being reviewed under FQPA. In addition, methyl bromide will become unavailable during the proposed project period due to its U.S. EPA phase-out of production and importation by 2005. Both locally and nationally, the agricultural production community (our stakeholders) is scrambling to find viable alternatives to chemical-based soil pathogen and nematode control. In addition, world travel and commerce have accelerated the dissemination of pest species, including plant-parasitic nematodes. The accurate identification of nematode species is beneficial and necessary for national and international regulatory and quarantine agencies relative to free trade and economics. The nematology community has repeatedly advocated the need for funding support focused on the basic and applied research required to advance alternative management approaches. The proposed project addresses these needs directly for the most important groups of plant parasitic nematodes, by building on advances made in the W-186 project over the last 10 years.

Importance of, and Consequences Without, the Work: The cyst and root-knot species are the most important groups of plant-parasitic nematodes in the United States. The management of these nematodes in United States agriculture during the past four decades has been largely via the application of broadly efficacious nematicides. Nematicidal activity, especially of soil fumigants, is generally non-discriminating, even between nematode species and genera. Therefore, understanding the genetic variability among nematodes was not important for effective nematode control. In contrast, desirable alternative nematode management strategies involve combinations of rotation, host plant resistance, cultural manipulations and biological control, all of which may have specific genotype-level interactions with nematodes and are influenced by environmental conditions. Hence, the genetic variability in nematode populations must be considered to successfully develop and deploy alternative management strategies. This regional project was initiated because the membership recognized the increasing importance of characterizing the genetic variation in nematode populations and its influence on success of alternative nematode management strategies. An example highlights the value of this project: Years of research went into the development of cyst-nematode resistant soybeans but the potential benefits of the resistance were limited due to the rapid selection of resistance-breaking nematode isolates.

A dramatic shift in nematode-management strategies is occurring, from almost exclusive reliance on soil-applied nematicides, to the use of combinations of alternative strategies such as crop rotation, host plant resistance, cultural manipulations and biological control (Ferris et al., 1992). An important difference from nematicides is that the alternatives are influenced directly by genetic variability existing in target nematode field populations. Hence, the successful use of alternatives requires more information to implement than nematicide-based strategies. Herein lies the logic and raison djtre of W-186 and its proposed revision: assessment and characterization of genetic variability extant in nematode populations will assist in the successful application of alternative management approaches, in addition to guiding initial development and deployment of new strategies. For example, knowing the frequency of virulence genes in a nematode population will allow deployment of corresponding resistance genes so that the utility of the resistance genes in new cultivars is maintained over time.

Except in the clearly demonstrable instances where resistance-breaking nematode populations are detected, the subtle influence of genetic variability in nematode populations has been considered only to a limited extent. However, the research conducted under the current W-186 multistate project has provided considerable evidence that this variability is important. We hypothesize that genetic variability in nematode populations is responsible for the aberrant results of many experiments assessing resistance, crop rotations, host ranges, cover/trap cropping, and biological control. The plasticity of nematode responses to abiotic environmental factors such as temperature, moisture, and host nutrient status stems from genetic variability, and such responses are poorly characterized. Greater understanding of nematode genetic response and adaptation to abiotic factors will be important in optimizing the design of cultural management tactics such as manipulations of planting and harvest times, wet or dry fallow, and soil solarization.

Without the proposed work continuing in a coordinated manner, the participants believe that effective nematode management alternatives will be developed more slowly, with success coming more on an ad hoc basis and with economic inefficiencies and a high likelihood of short-term failure of new products or management approaches. Knowledge gained from our main focus on cyst and root-knot nematodes also will be applied and tested on other important nematode groups within the revised project (see Table 1 matrix in Attachment). This will strengthen the overall scientific scope of the research activities and will broaden the impact of the findings to benefit agriculture in multiple states.

Technical Feasibility of the Research: New molecular and genetic methodologies and knowledge will facilitate the study of nematode genetic variability at much greater resolution than has been possible. Development of interactive database programs that provide information and advisory information on combinations of nematode management tactics will facilitate the adoption of integrated nematode management. Such on-line databases and knowledge-based systems will assist in information transfer to user groups in the relevant agricultural communities.

The root-knot and cyst nematodes are distributed throughout the United States and are damaging pathogens, parasitizing a wide range of important crops. Three groups of nematodes are the primary focus for this project: Group I - The warm-temperature root-knot species (Meloidogyne incognita, M. javanica, M. arenaria); Group II - The temperate root-knot species (M. chitwoodi and M. hapla); Group III - The cyst species (Heterodera schachtii, H. cruciferae and H. glycines). These nematodes are the subject of research efforts in the designated participating states. Current research is addressing many areas of management for these three groups, including: development and deployment of nematode-resistant plants; rotation to reduce population densities of these pathogens; cover crops and trap crops to reduce population densities; characterization of resistance genes and resistance responses; and the development of biochemical and molecular diagnostics for nematode identification. Thus the project participants share a strong common interest that will provide the central focus for the project members and other collaborators. In addition, parallel studies will be made by some participants on other endoparasitic nematodes, including reniform nematode (Rotylenchulus reniformis) and lesion nematodes (Pratylenchus spp.), and important ectoparasitic nematodes, including stubby root (Paratrichodorus spp.) and dagger (Xiphinema spp.) nematodes. This will maximize both the scientific scope of the project and its multi-state impact in agriculture.

Characterizing genetic variability  requisite for novel management strategies: The unifying theme of this proposal is that genetic variability is a critical biological feature of species and populations of the highly specialized plant parasitic nematodes. W-186 participants and others have begun to document the extent of genetic variability within populations, and the factors that influence it. New developments in molecular biology techniques and their application through this project will continue to increase our understanding of the genetic processes involved. As understanding of genetic variability in nematode populations increases, it has become clear that the race concept and other means of characterizing nematode population differences is inadequate. Failure of current nematode management, such as breakdown of resistance, and successful development of novel approaches can be resolved through greater understanding of the underlying genetic and biological processes in parasitic nematode populations vis a vis management. For example, the importance of mutation compared to maintained variability in field populations is unclear, and this is a research area that will be pursued.

Genetic variability can impact both the effectiveness and longevity of alternative nematode-management strategies based on host plant resistance, crop rotation, cultural manipulations and biological control. As a consequence, greater understanding of genetic variability should provide rational guidance for the design and development of management strategies. The W-186 project has focused on understanding nematode genetic variability, such that it can be identified, characterized, and managed or manipulated to benefit agricultural production systems. The underlying principles to this focus require research on the phenotypic and genotypic characterization of variability and gene frequencies, including aspects of stability and adaptability, of host range, response to resistance, response to environmental conditions, biological processes (e.g. fecundity) and morphology. This approach is being complemented and aided by development of markers to identify variability by molecular, biochemical, histochemical, and morphological polymorphisms. The development of molecular techniques with greater efficiency, predictability and ease of use will expedite the nematode genetic analyses and design of management systems. Current and previous work under W-186 has allowed participants to make advances on these research goals. However, much remains to be accomplished in this rapidly evolving research area. Accordingly, the research initiated under W-186 cannot be considered complete. Relative to our objectives, it is exciting that the arsenal of new tools used to address our applied research questions is increasing rapidly (e.g., Atkinson et al., 2001; Cai et al., 1997; Grosberg et al., 1996; Ibrahim et al., 1997; Karl and Avise, 1993; Lynch, 1996; Ouedraogo et al., 2002; Powers et al., 2001; Sambrook and Russell, 2001; Vos et al., 1995; Williams et al., 1990).

Four key considerations based on nematode genetic variability are central to development and deployment of alternative management strategies as proposed under this multistate project:

 Host plant resistance  The genetic composition of nematode populations is changed by the selection pressure imposed by growing resistant cultivars. The changes include shifts in species composition, and shifts in presence and frequency of nematode virulence alleles matching specific resistance genes in crop cultivars. Similar potential shifts may occur in response to nematode-resistant trap crops. Little is known of the existing frequency of virulence alleles, the frequency with which new alleles are generated, or the underlying mechanisms that regulate changes in genetic variability in root-knot and cyst nematode populations. As more sources of resistance are bred into cultivars, knowledge of gene frequency and stability effects assumes greater importance in determining the direction and requirements of breeding for nematode resistance, and the effective long-term deployment of available resistant cultivars (Starr et al., 2002).

 Host range for rotations and cover-cropping - The host ranges of important nematode species have been defined within general limits, but the extent of variability in host range among populations within species is not well-characterized. Thus, although most cyst nematodes have narrow host ranges and are amenable to control by nonhost rotation programs, little is known about the extent of reported hosts outside the typical host taxa, or the likelihood of shifts in host range. For example, although sugarbeet cyst nematode hosts are found almost entirely within the Brassicaceae and Chenopodiaceae, tomato (Solanaceae) has been reported to host this nematode in California and Utah, with potentially serious consequences for rotation planning in western sugarbeet production areas. Evidence for genetic adaptations and modification of nematode host range has also been presented whereby local nematode populations are better adapted to local weed populations. The processes involved in these interactions are poorly understood.

In contrast to cyst nematodes, root-knot nematode species have broad host ranges of more than 2000 plant species from diverse plant families. Much of this host range information has been compiled from numerous tests and observations based on non-standardized host testing procedures, and in most cases with only one or a few isolates of a root-knot species. Standardized conditions are needed to determine whether differences are due to variability in nematode populations or to differences in susceptibility in the plant lines used. Resolving the true levels and stability of host range relationships will be critical to development and implementation of non-host crops in rotation and cover-cropping programs, and for determining the role that host weed species play in maintaining nematode population levels.

 Cultural controls - Most are based on manipulating abiotic effects on nematode populations to suppress nematode activity or infection. Examples include wet or dry fallowing so nematodes starve while active (wet fallow) or die from extreme moisture stress (dry fallow). Soil solarization involves natural heating of soil under plastic cover to attain the thermal death point of nematodes. Avoidance may include changes in planting and harvest dates, such as delaying planting in the fall to avoid infection activity, and early planting or late harvest of crops to avoid additional nematode generations. Genetic variability in nematodes for response to temperature and moisture has been demonstrated, but it is not known how quickly or how stable such adaptive changes are, nor their frequency.

 Biological controls - Some potential biological control agents of cyst and root-knot nematodes are known to have specific host ranges among target nematode species, such as the host specificity of the bacterium Pasteuria penetrans among root-knot nematode species and populations. Such specificity may be controlled genetically, through surface protein binding and recognition between bacterium and nematode, suggesting that genetic variability in Meloidogyne may influence the potential of the bacterium and similar organisms as useful biological control agents.

Advantages of a Multistate Effort: During the previous life of this project, the membership effectively initiated research to apply emrging methodologies to obtain knowledge of the genetic variability in nematode populations. The W-186 membership proposes to continue and extend our efforts in this regard, to identify and characterize the genetic variability in the most important cyst and root-knot nematode groups and other important nematodes. The participants share research interests on primary nematode pathogens and bring complementary expertise to the project. In this iteration of the project, we will address gene frequencies, genetic stability, and adaptation and fitness, such that genetic variability can be managed and manipulated in agricultural production systems by appropriate alternative management strategies. The cyst and root-knot species are of primary importance as major nematode pathogens in most agricultural production areas and cropping systems throughout the United States. This is reflected in the proposed contributions from participating states across the country. The diversity in cropping systems and rank of importance of nematode groups among participating states clearly provides opportunities for conducting meaningful collaborative research on major nematode pathogens exposed to similarities and variations in crop (host), resistance, environmental and agroecological conditions. Via this project, the participants utilize the opportunity to collaborate in ways that enhance the benefits accrued from the research, as opposed to what might be gleaned if the researchers were to simply pursue individual projects within limited geographic boundaries. For example, the cool climate root-knot species will be studied by participants from nine of the 11 participating institutions in 10 states (see Attachment Table 1 Attachment)  a group effort that will pay large dividends in understanding nematode population genetics relative to management.

We believe that the similarities in the target nematode groups and the problems for nematode management imposed by genetic variability can be researched most efficiently through this coordinated multistate project. This team approach enables a pooling of scientific expertise and resources to maximize the amount and quality of the information that can be generated. The resources available to researchers working within the Agricultural Experiment Stations have been continually declining in recent years, and are particularly limited for nematology programs at this time. Conversely, the demands and expectations for new, environmentally friendly management tactics have never been greater. Accordingly, the membership has experienced a do more with less environment. This multistate project can provide some relief, as a necessary forum for rapid scientific advancement in aspects of both basic and applied research directed toward development of alternative management strategies. For example, it is unlikely that all participating states will have programs devoted to molecular research on nematodes, and yet the need for molecular-level approaches to assess genetic variability is required to address significant problems. This project has ongoing molecular-based programs in a few states (e.g. California, Hawaii, Nebraska, New Mexico) that can act to facilitate research by other participant states. In turn, those states focusing on phenotypic differences in nematode populations can provide nematode populations and isolates for the molecular scientists. This coordinated approach minimizes unnecessary duplication of research programs, and provides fertile opportunities for a seamless, interactive approach to development of integrated nematode management. Most importantly, the project also enhances the quality and applicability of the research findings across geographic locations and agricultural production systems. Likely Impacts of Work: The application of the project findings should expedite the development of new, environmentally benign management strategies to minimize economic losses from nematodes. This in turn should help boost the international competitiveness of our agricultural production systems, at a time when competitive advantage is being eroded by the loss, and potential further loss, of nematicides.

Related, Current, and Previous Work:

Related, Current and Previous Work: Accomplishments (1998-2003): A full listing of the research publications of the W-186 project from 1998-2003 is given in the attached Appendices. Following is a summary of the findings that highlights the areas of significant impact in addressing the project goals, with comments concerning the need for additional research.

Overall, the project scientists have been very productive in efforts to develop improved understanding of nematode genetic variability, processes of nematode fitness and adaptation, and the incorporation of this knowledge into the design and analysis of improved nematode management strategies. These findings directly benefit the 11 participating states and more broadly other states whose crop production systems are compromised by cyst and root-knot nematode infestations. Moreover, many of the accomplishments have resulted from our close collaboration within W-186, through which shared knowledge, techniques and materials has provided important synergies.

Under Objective 1 (characterize genetic variability as related to resistance, environment, biological processes and morphology), nematode (a)virulence and plant resistance gene interactions were elucidated genetically in several important nematode crop combinations. These included root-knot nematode interactions with resistance gene(s) and nonhost determinants in cotton, cowpea, common and Lima beans, potato, tomato, wheat, chile pepper, plus others. Cyst nematode interactions for (a)virulence matching host resistance have been defined to varying levels in sugarbeet, soybean and wheat. Within these interactions, new resistance specificities have been identified, such as the Rk genes in cowpea, together with the existence and frequency of matching virulence in nematode populations and their geographic distribution. These studies have been used to guide plant breeders and in the planning of crop rotations and cultivar selection. Molecular approaches to nematode identification within and between species has also been successfully pursued under this objective. Molecular techniques have been applied to or developed for identifying species of both the warm and cool climate root-knot nematode species, races and populations, and also sugarbeet, soybean and cereal cyst nematodes and their poulations. Project scientists also documented variability at the molecular level in some related nematode groups including lesion nematodes in small grain-potato cropping systems.

Under Objective 2 (determine nematode fitness and adaptability relative to environment, host plant and host plant resistance), several systems have been analyzed, revealing high levels of nematode adaptation to parasitic ability on resistant host plants, alternative hosts (weeds), and seasonal climatic differences. Variation in parasitic ability among root-knot nematodes was described for species parasitizing grain legumes such as cowpea and Lima bean, common beans, tomato, and potato cultivars and wild relatives. These studies demonstrated the need for broad-based forms of resistance for use in crop cultivars and cover and trap crops. In M. incognita populations virulent to resistance in cowpea, reduced fitness in the form of lowered fecundity and increased extinction rates we found associated with virulence, contributing to our understanding of nematode adaptation rates. In chile production systems, the reproduction levels by root-knot nematode populations were shown to be influenced by the presence of yellow and purple nutsedge species, demonstrating that previous or alternative hosts can change the parasitic ability of populations on crop plants. In addition, project scientists identified local adaptations in root-knot nematode populations to temperature regimes during the potato season in the Pacific Northwest, demonstrating the need to adjust predictive models for completion of nematode generations that influence decisions on time of harvest. Studies in Michigan showed that soil texture influences soybean cyst nematode population density in the field, although the role soil texture plays in altering H. glycines parasitism and adaptation is not yet known.

Under Objective 3 (design and develop management strategies for cyst and root-knot nematodes relative to genetic variability), root-knot and cyst nematode management systems have been studied, developed or improved for several cropping systems and production areas. In California, annual field and vegetable crop systems have been enhanced for root-knot nematode management utilizing host plant resistance in tomato, cotton, carrot and grain legume crops. Similarly, chile pepper and cotton production systems in New Mexico have been modified for root-knot nematode management, incorporating agronomic practices for weed host control and use of resistant chile cultivars. In the Pacific northwest, potato production systems have been examined and modified to optimize the choice of rotation crops and timing of production practices for managing the root-knot species M. hapla and M. chitwoodi. Likewise, sugarbeet product systems in California and Wyoming have been adjusted based on W-186 studies to utilize trap cropping and modified rotation sequences for cyst nematode management. These are selected examples of many advances in nematode management that are being made under W-186 participation, and they are at various stages of development that require additional study and modification.

Finally, a host plant and nematode database called NEMABASE has been further developed and expanded to incorporate project findings together with core information obtained from the published literature. NEMABASE can be interrogated directly via the UCD Dept. of Nematology WWW homepage: (http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/contents). NEMABASE is also distributed through the University of California Integrated Pest Management (UCIPM) program, and can be downloaded from the UCIPM web site (http://www.ipm.ucdavis.edu). A knowledge-based system ("KNOWLEDGE") using NEMABASE as a core database has also been developed and expanded through W-186 and other scientists participation. There are now more than 32,000 records in KNOWLEDGE. W-186 members have a CD ROM version with the updated databases for project use and sharing with stakeholders.

Areas Needing Further Investigation: Many of the cropping systems we are studying involve complex, multi-year rotations requiring several years of experimentation to test the various permutations of cropping sequences and the durability of resistance relative to nematode selection for virulence and nematode adaptation to environment and to other control measures. Efforts under W-186 have laid the foundations for integrating new approaches to nematode management that consider the genetic variability extant in nematode species. Additional study and modification of these systems for managing nematodes is necessary in order to design and optimize new integrated strategies. Coupled with these efforts, molecular markers are being added with the application of new techniques for molecular fingerprinting of genotypes and for tracking nematode virulence and resistance traits. The continuing reduction in nematicide usage, availability and overall desirability and cost effectiveness, places added pressure on our need to develop alternative nematode management strategies, a primary goal of the proposed project.

Other Regional Projects: The only current multistate project with potential overlap to this proposal is S-282 (Managing Plant-Parasitic Nematodes in Sustainable Agriculture with Emphasis on Crop Resistance), that focuses primarily on cotton, peanut and soybean cropping systems of the southaestern U.S. It emphasizes resistant variety development and emphasizes soybean cyst nematode and especially reniform nematode, in contrast to the current proposal. Thus, while portions of its goals are similar to the current proposal, it focuses primarily on host plant resistance and a different set of cropping systems to the ones proposed herein. In 1999 a joint meeting of W-186 and S-282 was held for sharing and coordination of the relevant research interests; we will plan to do this again.

Objectives

  1. Define nematode genetic variability for phenotypes including morphology, responses to resistance, environmental variation, and biotic interactions.
  2. Determine nematode fitness and adaptability relative to environment, host plant, and host plant resistance.
  3. Design and develop integrated management strategies for plant-parasitic nematodes that include consideration of environment and genetic variability.
  4. Implement rapid information transfer of project results to stakeholders.

Methods:


Methods: The research focus of each participating state is given as a matrix in Table 1. The nematode group and main crop areas are indicated, together with the procedural research emphasis, as covered under the four objectives. Research coordination will ensure that standardized procedures are generally followed and research findings can be compared within and across nematode, plant and subject area categories. Plant germplasm (accessions, breeding lines, cultivars), nematode isolates of representative species and populations, and DNA probes for markers will be available among the participants

Experimental protocols and procedures are structured according to the main target nematode groups under the four objectives. All objectives have a common focus of addressing critical aspects of nematode genetic variability, with the application and extension of the findings tailored to meet individual state and sub-regional needs, in addition to those at the project-wide level. While findings under all objectives are considered important to each state, duplication will be avoided by partitioning individual state research activities. This structure will also ensure that all phases of the objectives are being met, while addressing local state needs. For example: Heterodera schachtii will be considered in California, Hawaii, Idaho, and Wyoming; Heterodera glycines will be considered in Arkansas, Michigan, Nebraska, and Tennessee, while the Group II cool-climate root-knot species (Meloidogyne chitwoodi and M. hapla) will be studied in detail in California, Michigan, Nebraska, Oregon, Idaho, and Washington and Wyoming. However, Oregon, Idaho, Washington, and Wyoming will focus on potato and (or) small grain interactions, while Washington and California will focus on host-plant resistance. Oregon, Idaho, New Mexico and Wyoming will address host range and rotations, while California, Idaho, and Wyoming will address cover-cropping. Similar partitioning of research activity will be made for the other nematode groups.

Objective 1: Phenotypic assessments will be made on isolates of nematode populations that are collected following survey and documentation of habitat, locality, and agronomic or cropping history of the collection site. This information will provide important background considerations for the level and nature of any phenotypic differences detected in comparative experiments. In most programs, investigators either have a partial or nearly complete collection of live cultures for genetic comparisons. For example, 25 isolates of warm-climate root-knot populations have been assembled at California-Riverside, and collections of M. chitwoodi isolates are maintained in Oregon and Washington. For cyst nematodes, numerous populations of H. glycines are being cultured in Arkansas, Michigan and Tennessee, and a collection of H. schachtii and H. cruciferae geographic and host-selected isolates is under culture in Hawaii and California-Davis.

Assays of (a)virulence response to resistant lines and cultivars and of host range will be made under greenhouse and controlled environment conditions using well-established experimental procedures. The host range and virulence testing for the root-knot species (Groups I and II) will include standard sets of host differential plants and also differential cultivars and crop plants applicable to their local cropping systems. The biotype scheme for root-knot nematode virulence will be expanded using known accessions, breeding lines, and cultivars of critical crops. The cyst nematodes H. glycines will be examined on resistant soybean differentials and H. schachtii on sugarbeet breeding lines with resistance, while the endoparasitic nematode Rotylenchulus reniformis will be examined on pineapple lines in Hawaii and cotton in Tennessee.

The cyst nematodes are excellent "model" nematode systems for genetic studies because they reproduce sexually. Conversely, many root-knot species are parthenogenetic (asexual). Their genetics will be studied using isofemale or single descent lineages to track inheritance, variability and adaptation, and via mendelian approaches using spieces that can reproduce sexually, such as M. hapla and M. chitwoodi. This work was initiated under the current W-186 project and several valuable segregating populations have been created. Current standard molecular biology techniques will be used for this objective, and the protocols and techniques, although new, are well established. Techniques for RFLP analysis of genomic and mtDNA are well established in many participants' laboratories. Techniques of AFLP, ASCN, and SSR will be combined with transmission genetics of phenotypes of interest to conduct analyses of markers and associated traits. Meloidogyne and Heterodera populations will be typed phenotypically for (a)virulence with respect to numerous host-plant resistance genes from different crop plant species and close wild relatives, for host range, and for other biological traits. Molecular marker analyses of these populations will lead to stable marker systems for nematode (a)virulence phenotypes, host range determinants, and geographical variants for diagnostic purposes, using mtDNA, RFLP, AFLP, SSR, and ASCN markers. This will also allow us to monitor changes in gene frequency in fields, as we subject field populations to different cropping sequences. Different states will focus on particular species in a collaborative framework: e.g., M. incognita populations from cotton-producing states, including California, New Mexico, and Tennessee; M. chitwoodi and M. hapla in the potato-small-grain-alfalfa systems of Oregon, Washington, and Idaho; H. schachtii, H. glycines, and H. cruciferae from California, Hawaii, Michigan, Nebraska, Tennessee, Wyoming.

Objective 2: Phenotypic characterization and genetic markers developed under Objective 1 will provide the basis for selecting candidate populations that show adaptation to increased virulence and parasitism, and for variants associated with geographic (climatic) isolation and adaptation. The fitness of isolates virulent for specific resistance genes will be assessed by controlled culturing on susceptible plants for multiple generations. Effects of non-agronomic hosts on fitness will be examined, including continuation of studies on the effects of nutsedges as weed hosts on root-knot nematodes in New Mexico cropping systems. Participants also will include comparisons with invasive root-knot nematode species, such as M. mayaguensis (Group II) and M. fallax (group III), which have heightened aggressiveness and broad host range.

Adaptation and fitness also will be studied by imposing continuous selection for virulence in wild-type populations. Changes in reproductive capacity will be assessed to measure virulence frequencies and genetic stability of virulence. Tests of selected isolates will be made on resistant or nonhost plants other than those used to impose the original selection pressure. For example, in California studies have been initiated using a model system of M. incognita (a)virulence matching resistance gene Rk in cowpea. In the field, changes in virulence in H. glycines toward a soybean cultivar carrying specific resistance will be monitored.

In addition, fitness and adaptability of H. glycines races, M. hapla and M. incognita to changes in soil nutrition and soil physio-chemical environments will be tested, focusing on sources of nitrogen and types and levels of nutrients and their affects on host plant status. Quantifying nematode adaptability to changes in soil-nutrient environments, a major emphasis of work in Michigan, will aid our understanding of possible factors contributing to nematode adaptations.

Objective 3: A range of factors and approaches will be considered in the design of nematode management strategies under Objective 3 - soil ecology and other soil properties, nematode community structure and function, sampling strategies tied with opportunities afforded by precision agriculture technologies for site-specific management. The integration of host resistance, cover and trap crops, tillage practices and impact of biological antagonists in crop rotation sequences will be considered in practical combinations and locations. The development of biotyping schemes for cyst and root-knot nematode populations for reaction to host and nonhost crops and to resistant cultivars, and accompanying practical marker systems under Objective 1will provide important information for resistance implementation in annual crops. Crop rotation utilizing only nonhosts as production or cover crops grown in rotation with hosts will be evaluated for success in nematode management and profitability. Knowledge on nematode fitness and adaptability developed under Objective 2 will aid in the optimization of durable nematode management strategies. Climatic and soil conditions, different nematode species, and variability in host ranges among different populations will require unique rotations for different growing regions. Several cropping systems being evaluated currently under W-186 have multi-year horizons and crop sequence combinations that require much additional analysis. Rotation schemes will be assessed in microplots or infested field sites within the relevant localities. Techniques will be coordinated among participants to facilitate direct comparisons of results.

Objective 4: Transfer of this information as guidelines to growers, pest control advisors, commercial and public plant breeders, and seed company personnel will involve the development of written materials, together with the use of a computerized database format that can be accessed centrally as described below.

Information regarding the host status of plants to different nematode species is necessary to design rotations. At California-Davis under the W-186 project, Dr. Caswell-Chen has created a personal computer database (Caswell-Chen et al., 1995) of current, accessible information on nematode-plant interactions (accessible via the WWW using a standard browser that is pointed to the following address: (http://ucdnema.ucdavis.edu/Tango/Tango.acgi$/Tutorial/INTERACT.QRY?function=form). The goal is to complete a database that will provide information on resistant cultivars, rotations, and cover-crops for nematode management; currently it contains 45,000 records on nematode-plant interactions, culled from the primary nematological literature. Access to information via the WWW only assists in implementation, because access to informational databases is only one component necessary for application of knowledge. Database content will be modified by participating states. The database will assist in defining acceptable rotations or selection of resistant cultivars, and will allow evaluation of genetic variation within species across wide geographic areas.

A goal for database utility is the user to provide input to the system, including: nematode species, nematode race, nematode density, crop sampled, desired crops for the next three years, willingness to use nematicides, soil type, geographic location, and management priority (improving yield, growing high value crop, prefer short- or longer-term benefits). In response, the user will be informed of the suitability of the planned cropping sequence; the plants and cultivars resistant to their problem nematode; possible beneficial crop sequences; nematicides that could be used; and, an economic synopsis of costs for management.

Linked to the general database will be a WWW site designed specifically to report project results in a stakeholder-friendly format. Participant Dr. P. Donald, Tennessee will act as webmaster. This format will include description of management options using knowledge-based summaries of options for specific nematode-crop systems. Advice on sampling strategies and fast identification procedures will also be included, as will linkage to the Purdue NAPIS site for georgaphic map databases. In addition, presentations and workshops for delivery of project progress and findings will be conducted by project participants and their CE colleagues in the participating states.

Measurement of Progress and Results:

Outputs:
Outcomes or projected Impacts:
Milestones:

(): The research will provide information necessary to implement nematode management alternatives to nematicides. For each nematode or cropping system included, a sequence of progressive steps based on the order of the objectives will include developing new basic knowledge, from which a control strategy is developed, that in turn is advanced toward implementation by field experimentation and demonstration. For example, identification of resistance in a crop, advancement of the trait into commercial varieties and testing its effectiveness in a cropping system rotation will be made. The nematodecrop plant combinations and cropping systems included in the project are at different stages of progression. Thus, each will have its own timeline for completion, but typically will require completion of the objectives in the order presented; thus, Objectives 3 and 4 will require completion of Objectives 1 and 2 for a given nematode-crop system.

Projected Participation:

Include a completed Appendix E form

Outreach Plan:

The project has a successful track record of disseminating the new knowledge and information created by participants and co-operating colleagues, including most recently the Web-accessible nematode management database. It is planned that the traditional outlets for transferring project results will continue to be utilized, including peer-reviewed journals, annual progress reports and scientific meeting presentations, the described websites and databases. Extension presentations and publications will also be made, both by participants with extension appointments, and by AES and ARS participants, most of whom have a strong applied research component to their programs and who routinely participate in extension-based activities (meetings, presentations, publications) with our agricultural stakeholders.

Organization and Governance:

The organization and governance of the Proposed Multistate Research Project will conform to the guidelines presented in the United States Department of Agriculture's publication "Manual for Cooperative Regional Research". Committee officers include a Chair, a Vice-Chair, and a Secretary. A new secretary is elected at each annual meeting of the Technical Committee with the current secretary assuming the position of Vice-Chair. The Vice-Chair assumes the position of Chair at the end of the annual meeting. In the event that an Executive Committee is needed, the officers are authorized to serve in that role. Administrative guidance will be provided by an assigned Administrative Advisor and a CSREES Representative.

Literature Cited:

W-186 Publications (1998-2003)_

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Hafez, S.L. and P. Sundararaj. 1999. Efficacy of seed crop meals for the management of Columbia root-knot nematode Meloidogyne chitwoodi on tomato under green house conditions. Nematropica. 29 : 171 - 177.

Hafez, S.L., D. Miller and P. Sundararaj. 2000. Screening of alfalfa cultivars to the lesion nematode Pratylenchus penetrans for commercial release. Nematologia Mediterranea. 28 : 157-162.

Hafez, S. L. and P. Sundararaj. 2000. Evaluation of mocap for management of Meloidogyne chitwoodi in Idaho potatoes. Nematropica. 30 : 130.

Hafez, S. L. and P. Sundararaj. 2000. Nematode management research in Idaho and it's impact on the growers economy. Nematropica. 30 : 130-131.

Hafez, S. L. and P. Sundararaj. 2000. Application and placement of nematicides in the management of stubby root nematode and corky ringspot disease of potato. American Journal of potato Research. 77: 400.

Hafez, S.L., Garo Haroutunian and P. Sundararaj. 2000. Biofumigation and bassamid - An alternative integrated approach to methyl bromide for vegetable and fruit production in Lebanon. Proceedings of the Annual International Research conference on Methyl Bromide alternatives and emission reductions, at Orlando, Florida, November 6-9, 2000.

Hafez, S. L. and P. Sundararaj. 2000. Resistant reaction of alfalfa cultivars to the lesion nematode Pratylenchus penetrans. Journal of Nematology. 32 : 433.

Hafez, S. L. and P. Sundararaj. 2000. Evaluation of fosthiazate for management of Meloidogyne chitwoodi in Idaho potatoes. Journal of Nematology. 32 : 433.

Hafez, S.L. and P. Sundararaj. 2000. Concomitant interaction of Meloidogyne chitwoodi and Pratylenchus neglectus in potato cropping system. Nematologia Mediterranea. 28 : 89 - 92.

Hafez, S. L. and P. Sundararaj. 2000. Evaluation of chemical strategies along with cultural practices for the management of Meloidogyne chitwoodi on potato. International Journal of Nematology. 10: 89 - 93.

Hafez, S. L. and P. Sundararaj. 2000. Resistant reaction of alfalfa cultivars to the lesion nematode Pratylenchus penetrans. Presented at the "39th Annual meeting of Society of Nematologists" held at Quebec, Canada June 24-28, 200. Also abstract published in the Journal of Nematology. 32 : Hafez, S.L. and P. Sundararaj. 2001. Screening bean cultivars and germ plasm for nematode resistance. Proceedings of the "Idaho Bean Field Day" organized by the Idaho bean commission and the University of Idaho at Parma on August 9, 2001. 10 - 12.

Hafez, S.L. and P. Sundararaj. 2001. Non-chemical alternatives for sugarbeet cyst nematode management in Idaho. Proceedings of the "Annual International Conference on Methyl bromide alternatives and emission reductions" held on Novemebr 5-9, 2001 at San Diego, California. 86-1 to 86-4, 2001.

Hafez, S. L. and P. Sundararaj. 2001. Integrated nematode management in Idaho. Proceedings of the "Plant Protection Seminar, An intensive, practical short course for the agrichemical business person and farmer" held at College of Southern Idaho, Twin Falls, Idaho from November 12 -13, 2001. 18 - 39.

Hafez, S.L. and P. Sundararaj. 2001. Chemical nematicides for the suppression of Meloidogyne chitwoodi and M. hapla on potato. International Journal of Nematology. 11 : 192 -194.

Hafez, S.L. and P. Sundararaj. 2001. Impact of nematode management options on the yield and nutrition status of potato, solanum tuberosum. International Journal of Nematology. 11 : 195-199.

Hafez, S. L. and P. Sundararaj. 2001. Impact of green manure crops on sustainable management of sugar beet cyst nematode. Presented at the "Joint Meeting of American Phytopathological Society, Mycological Society of America, Society of Nematologists (SON)" held at Salt Lake City, Utah August 25 - 29, 2001. Also abstract published in the journal Phytopathology (supplement). 91 : 6, s134-s135.

Hafez, S. L. and P. Sundararaj. 2001. Efficacy of oil seed meals for management of Heterodera schachtii and Meloidogyne chitwoodi under green house conditions. Presented at the "Joint Meeting of American Phytopathological Society, Mycological Society of America, Society of Nematologists (SON)" held at Salt Lake City, Utah August 25 - 29, 2001. Also abstract published in the journal Phytopathology (supplement). 91 : 6, S-135.

Hafez, S.L. and P. Sundararaj. 2002. Integrated nematode management options for the sustainable potato production. Proceedings of the " University of Idaho Winter Commodity Schools - 2002 ". 111-116.

Hafez, S.L. and P. Sundararaj. 2002. Sugarbeet cyst nematode management options in Idaho. Proceedings of the "University of Idaho Winter Commodity Schools - 2002". 231-236.

Hafez, S. L. and P. Sundararaj. 2002. Screening bean cultivars to Meloidogyne Chitwoodi and M. hapla as an option for nematode management in potato fields. Presented at the "Sixth conference of Applied Zoologists Research Association" on 'Advances in Applied Zoological Researches for Food Production and Environmental safety' held in Cuttack, India from December 19 - 22.

Hafez, S. L. and P. Sundararaj. 2002. Impact of oil radish and white mustard for the effective sugar beet cyst nematode management. Presented at the "Sixth conference of Applied Zoologists Research Association" on 'Advances in Applied Zoological Researches for Food Production and Environmental safety' held in Cuttack, India from December 19 - 22.

Hafez, S. L. and P. Sundararaj. 2002. Nematode diversity and agricultural sustainability in Idaho. Presented at the "Sixth conference of Applied Zoologists Research Association" on 'Advances in Applied Zoological Researches for Food Production and Environmental safety' held in Cuttack, India from December 19 - 22.

Hafez, S. L. and P. Sundararaj. 2002. Chemical options for the management of Heterodera schachtii in sugar beet under field conditions. Hafez, S. L. and P. Sundararaj. Presented at the "Fourth International Congress of Nematology (FICN)" held at Canary Islands, Spain June 8 - 13, 2002. Also abstract published in the Journal Nematology. 4 :1, 295.

Hafez, S. L. and P. Sundararaj. 2002. Evaluation of nematicides for the management of Meloidogyne chitwoodi on potato in Idaho. Presented at the "Fourth International Congress of Nematology (FICN)" held at Canary Islands, Spain June 8 - 13, 2002. Also abstract published in the Journal Nematology. 4 :1, 295-296.

Hafez, S. L. and P. Sundararaj. 2002. Comparative efficacy of fosthiazate formulations for the mangement of Meloidogyne chitwoodi. Hafez, S. L. and P. Sundararaj. Presented at the "Fourth International Congress of Nematology (FICN)" held at Canary Islands, Spain June 8 - 13, 2002. Also abstract published in the Journal Nematology. 4 :1, 296.

Hafez, S.L., P. Sundararaj and G.W. Harding. 2001. Bioecology and basic IPM for potato nematode. Proceedings of the "Potato nematode workshop" held at Pocatello on January 17, 2001. 167 - 171.

Hafez, S.L., G. Haroutunian, R. Khoury, and P. Sundararaj. 2002. Preliminary report on the methyl bromide complete phaseout investment project in Lebanon. Proceedings of the "Annual International Conference on Methyl bromide alternatives and emission reductions" held on Novemebr 6-8, 2002 at Orlando, Florida. 11-1 to 11-2, 2002.

Hafez, S.L., P. Sundararaj and D. Miller. 2002. Reaction of twenty-one alfalfa cultivars to the lesion nematode Pratylenchus penetrans and the root - knot nematode Meloidogyne chitwoodi. Proceedings of the "North American Alfalfa Improvement Conference" held at Sacramento, California from July 27 to 31, 2002.

Hafez, S.L., and P. Sundararaj. 2001. Impact of agronomic and cultural practices of green manure crops for the management of Heterodera schachtii in sugarbeet. International Journal of nematology. 10 : 177-182.

Hafez, S.L., P. Sundararaj and Gale W. Harding. 2002. Efficacy of placement of aldicarb for the control of stubby root nematodes and corky ring spot disease of potato. Nematologia Mediterranea. 30 : 227 - 229.

Hafez, S.L. and P. Sundararaj. 2002. Evaluation of autumn or spring application of Ethoprop for the management of Meloidogyne chitwoodi on potato. Nematologia Mediterranea. 30 : 159 - 161.

Hafez, S.L. and P. Sundararaj. 2002. Efficacy of seed crop meals for the management of Heterodera schachtii and Meloidogyne chitwoodi in pots. Nematologia Mediterranea. 30 : 181 - 183.

Hafez, S.L. and P. Sundararaj. 2002. Efficacy of chemical nematicides for the management of Meloidogyne chitwoodi on potato. 2002. International Journal of Nematology. 12 : 76 - 78.

Hafez, S.L. and P. Sundararaj. 2002. Chemical options for the management of stubby root nematodes on potato. 2002. International Journal of Nematology. 12 : 73 - 75.

Hafez, S.L. and P. Sundararaj. 2002. Evaluation of nematicides for the management of Columbia root-knot nematode in potato, 2001. Fungicide and Nematicide Tests. 57:10.

Hafez, S.L., P. Sundararaj and B. A. Hatjian. 2002. Fosthiazate 500 EC for control of Columbia root-knot nematode in potato, 2000. 2002. Fungicide and Nematicide Tests. 57:11.

Hafez, S.L., P. Sundararaj and R. Portenier. 2002. Application and placement of Temik, Vydate and Admire for control of stubby root nematode and corky ringspotdisease of potato, 1999. Fungicide and Nematicide Tests. 57:9.

Hafez, S.L., P. Sundararaj and R. Portenier. 2002. Fosthiazate 900 EC for control of Columbia root-knot nematode in potato, 1998. Fungicide and Nematicide Tests. 57:12.

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Melakeberhan, H. (2001). Embracing the emerging precision agriculture technologies-symposium introduction. Journal of Nematology, 33: in press.

Melakeberhan, H. (2002). Embracing the Emerging Precision Agriculture Technologies for Site-specific Management of Yield-limiting factors. Journal of Nematology, 34: 185-188.

Melakeberhan, H. (2003). Physiological interaction between nematodes and their host plants. In: Z.X. Chen, S. Y. Chen, and D. W. Dickson (eds.) Nematology, Advances and Perspectives. Volume I: Nematode Morphology, Physiology, and Ecology. Frontiers of Science and Technology for the 21st Century" Series. Tsinghua University Press, China. In press.

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Melakeberhan, H. and J. Dey. (2003). Competition between Heterodera glycines and Meloidogyne incognita or Pratylenchus penetrans: Independent infection rate measurements. Journal of Nematology, 35: In press.

Melakeberhan, H., A.L. Jones and G.W. Bird. (2000). Effects of soil pH and Pratylenchus penetrans on the pathogenesis of Pseudomonas syringae pv. syringae and Mazzard seedling mortality. Canadian Journal of Plant Pathology, 22: 131-137.

Melakeberhan, H., A. L. Jones and G.W. Bird. (2001). Soil pH affects nutrition balance of cherry rootstocks. HortScience, 36: 916-917.

Melakeberhan, H., A. L. Jones and G.W. Bird. (2001). Soil pH affects nutrition balance of cherry rootstocks. HortScience, 36: 916-917.

Ndeme, A., P. Donald, G. Noel, H. Melakeberhan, G. Tylka, S. Chen, R. Riggs, T. Niblack, D. Herschman, J. Faghihi, A. MacGuidwin, T. Welacky, and T. Anderson (2001). Soybean yield and Heterodera glycines population dynamics in the Midwestern U.S. and Ontario, Canada. Journal of Nematology, 33: in press.

Ogallo, J.L., P.B. Goodell, J. Eckert and P.A. Roberts. 1999. Management of root-knot nematodes with resistant cotton cv. NemX. Crop Science 39:418-421.

Ouedraogo, J.T., B.S. Gowda, M. Jean, T.J. Close, J.D. Ehlers, A.E. Hall, A.G. Gillaspie, P.A. Roberts, A.M. Ismail, G. Bruening, P. Gepts, M.P. Timko and F.J. Belzile. 2002. An improved genetic map for Cowpea (Vigna unguiculata L.) combining AFLP, RFLP, RAPD and biochemical markers and biological resistance traits. Genome 45: 175-188.

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Petrillo, M.D. 2001. Virulence and fitness of Meloidogyne incognita in response to susceptible and resistant cowpea. Ph.D. Dissertation, University of California, Riverside.

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Szalanski, A.L., P. G. Mullin, T. S. Harris, and T. O. Powers. 2001. First report of Columbia Root Knot Nematode (Meloidogyne chitwoodi) in potato in Texas. Plant Disease 85:422.

Sattell, R. R. Dick, R.E. Ingham, R. Karow, D. Kaufman, and D. McGrath. 1998. Rapeseed (Brassica campestris/Brassica napus). pp. 43-44. In: Sattell, R. (ed). Using cover crops in Oregon. Oregon State University Extension Service Publication EM 8704. 50 pp.

Sattell, R. R. Dick, R.E. Ingham and D. McGrath. 1998. Sudangrass and sorghum-sudangrass hybrids (Sorghum bicolor L.). pp. 49-50. In: Sattell, R. (ed). Using cover crops in Oregon. Oregon State University Extension Service Publication EM 8704. 50 pp.

Schroeder, J., S. H. Thomas and L. W. Murray. 2003. Root-knot-nematodes affect annual and perennial weed interactions with chile pepper. Weed Science 51: in press.

Shigaki, T., F.A. Gray, R.H. Delaney and D.W. Koch. 1998. Evaluation of host resistance and intercropping for management of northern root-knot nematode in sainfoin, Onobrychis viciifolia. Journal of Sustainable Agriculture 12:23-39.

Simon, P. W., W.C. Matthews, and P.A. Roberts. 2000. Evidence for a simply inherited dominant resistance to Meloidogyne javanica in carrot. Theor. Appl. Genet. 100:735-742.

Sipes, B.S. 2001. Spatial pattern of Radopholus similis in the roots and shoots of Anthurium andreanum. Nematropica 31:113-118.

Smith, H. J., F. A. Gray, D.W. Koch, J. M. Krall and L.J. Held. 2001. New technologies for integrated management of the sugar beet nematode, Heterodera schachtii. Phytopathology 91: No. 6 Supplement, S143.

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Thomas, S. H., S. A. Sanderson, and Z. A. Handoo. 2001. First report of Columbia root-knot nematode (Meloidogyne chitwoodi) in potato in New Mexico. Plant Disease 85:924.

Thomas, S. H., J. M. Fuchs, and Z. A. Handoo. 2001. First report of Meloidogyne partityla on pecan in New Mexico. Plant Disease 85:1030.

Thomas, S. H., J. M. Fuchs, and A. L. Jacobson. 2001. Meloidogyne partityla: an emerging nematode pest of pecan in New Mexico. Phytopathology 91:S144.

Thomas, S. H. 2001. The status of nematodes in western pecan orchards: what we know and what we don't. Thirty-fifth Western Pecan Conference Proceedings. March 4-6, 2001. Las Cruces, NM. Pp. 2-5.

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Tsang, M.M.C., A.H. Hara and B.S. Sipes. 2003. Hot-water treatments of potted palms to control burrowing nematode, Radopholus similis. Crop Protection 22:589-593.

Veremis, J.C., A.W. van Heusden and P.A. Roberts. 1999. Mapping a novel heat-stable resistance to Meloidogyne in Lycopersicon peruvianum. Theor. Appl. Genet. 98:274-280.

Veremis, J.C., and P.A. Roberts. 2000. Diversity of heat-stable genotype specific resistance to Meloidogyne in Lycopersicon peruvianum. Euphytica 111:9-16.

Wang, J., P. A. Donald, T. L. Niblack, G. W. Bird, J. Faghihi, J. M. Ferris, D. J. Jardine, C. Grau, P. E. Lipps, A. E. MacGuidwin, H. Melakeberhan, G. R. Noel, P. Pierson, R. M. Riedel, P. R. Sellers, W. C. Stienstra, T. C. Todd, G. L. Tylka, T. Wheeler, D. S. Wysong. (2000). Soybean cyst nematode reproduction in the north central United States. Plant Disease, 84: 77-82.

Wang, K.H., B. S. Sipes, and D. P. Schmitt. 2001. Suppression of Rotylenchulus reniformis by Crotalaria juncea, Brassica napus, and Tagetes erecta. Nematropica 31:235-249.

Wang, K.H., B. S. Sipes, and D. P. Schmitt. 2002. Crotalaria as a cover crop for nematode management: a review. Nematropica 32:35-57.

Wang, K.H., B. S. Sipes, and D. P. Schmitt. 2002. Management of Rotylenchulus reniformis in pineapple, Ananas comosus, by intercycle cover crops. Journal of Nematology 34:106-114.

Wang, K. H., B. S. Sipes, and D. P. Schmitt. 2003. Enhancement of Rotylenchulus reniformis suppressiveness by Crotalaria juncea amendment in pineapple soils. Agriculture, Ecosystems and Environment 94:197-203.

Williams-Woodward, J.L. and F.A. Gray. 1999. Seasonal fluctuations of soil and tissue populations of Ditylenchus dipsaci and Aphelenchoides ritzemabosi in alfalfa. Journal of Nematology 31:27-36.

Yun, L., D.W. Koch, F.A. Gray, D.W. Sanson and W. Means. 2000. Potential of trap crop radish for fall lamb grazing. Journal of Prod. Agriculture 12:559-563. McSorley, R.L. and S.H. Thomas. 2003. Diseases caused by nematodes. Pp. 46-49. In: Compendium of Pepper Diseases. K. Pernezy, P. D. Roberts, J. F. Murphy, and N. P. Goldberg, eds., APS Press. St. Paul, MN.

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