Duration: 10/01/2011 to 09/30/2016

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

The North Central Region (NCR) includes the major production areas of corn, soybeans, and small grains in the US. Each of these crops is susceptible to multiple species of plant-parasitic nematodes with the capacity to significantly limit production. In the case of soybean, the damage risk largely is concentrated in one species, the soybean cyst nematode (SCN), Heterodera glycines. This pest is widely distributed throughout the region and is recognized as the major yield-limiting pathogen of soybean, a crop that contributes $18 billion annually to the economy of the nation. Management tactics currently are limited to the use of nonhost crops, resistant soybean cultivars, and one or two soil-applied nematicides. Unfortunately, each of these management tactics has serious shortcomings. There is an urgent need to improve and integrate management tactics for control of this widespread, persistent, yield-decreasing soybean pest. It is our aim to conduct region-wide coordinated research directed toward reducing losses due to SCN.

The most recent loss estimates for corn-parasitic nematodes suggest an average loss of 1% across the NCR (Koenning et al. 1999). This is considerably lower than loss estimates across the region from a decade earlier (Society of Nematologists Crop Loss Assessment Committee, 1987), likely reflecting reduced emphasis on corn-parasitic nematodes among NCR nematologists. Recently, however, there has been a renewed focus on nematodes that parasitize corn because of concerns about unforeseen impacts on nematode pest populations resulting from changing corn production management practices, such as an increased focus on conservation tillage and a reduced reliance on traditional soil-applied insecticide-nematicides, and due to the development of new seed treatments for nematode protection and control. In contrast to the situation in soybean, there are several types of plant-parasitic nematodes that occur commonly, and often jointly, in corn production fields across the region and that have been implicated in crop damage. Principal among these are the root-lesion nematodes (RLN), with at least six distinct species encountered in NCR corn fields. Although damage relationships are well documented for several RLN species (Smolik and Evenson, 1987; Todd and Oakley, 1996), the risk of damage from other commonly occurring nematode genera and species or from complexes of multiple nematode species remains largely unknown for corn in the NCR. Furthermore, as management options are more limited for corn-parasitic nematodes compared to those for SCN, the need to improve and integrate management tactics is particularly urgent.

In order to effectively address the current and potential economic consequences of plant-pathogenic nematodes in the NCR, we have developed three near-term objectives for coordinated regional research:

1) Develop, evaluate, improve and integrate management techniques for plant-parasitic nematodes in the North Central Region to increase grower profitability;

2) Determine the relationships among nematode population characteristics, crop injury and soil health;

3) Develop tools for technology transfer for management of regionally important nematodes with special reference to soybean cyst nematode and corn parasitic nematodes.

The specific approaches identified to achieve these objectives fit very well within the following four NCRA Priority Research Objectives for Integrated Pest Management:

*Develop alternative controls based on biological control and cultural practices.

*Investigate the genetics of pests and hosts to identify new and different vulnerabilities that can be exploited in pest control strategies.

*Refine and develop rapid and positive pest detection and identification techniques to enhance the capability to predict the occurrence and magnitude of pest populations/infestations/infection.

*Reduce reliance on pesticides and the risk of human, animal and environmental exposure to pesticides.

Soybean cyst nematode management

Although a number of different management tactics have been investigated (Niblack and Chen, 2004), the only ones that consistently increase yields in infested fields or reduce SCN population densities, or both, are rotation to nonhost crops (such as corn) and the use of resistant soybean cultivars. The recommendation to grow two or more consecutive years of nonhost crops for management of the nematode is of limited utility because many of the fields in the NCR have corn and soybean grown in alternating years for economic and agronomic reasons; therefore, planting multiple years of nonhost crops for nematode management purposes often may not be an option. In the NCR, in contrast to the southeastern US, cultivation of a nonhost reduces SCN population densities only about 35 to 50% and overwinter survival is typically 100% (Jackson et al., 2006).

There are hundreds of soybean cultivars available with resistance to SCN, but more than 90% of the resistant cultivars contain resistance derived from the soybean plant introduction (PI) 88788 (Diers et al., 1998; Shier, 2005; Tylka 2010). Only a few soybean cultivars possess resistance from the soybean lines PI 548402 (Peking) and PI 437654 (the source of resistance in the CystX® germplasm). Soybean cultivars with resistance derived from PI 88788 and PI 548402 allow some level of reproduction by most SCN populations. Consequently, selection for populations of the nematode that can readily reproduce on the resistant soybean cultivars can occur when resistant cultivars are used repeatedly. For example, in a 1990 Illinois survey, researchers found that only about 34% of SCN populations in the state could attack PI 88788 and cultivars derived from it (and marketed as resistant), and none of these nematode populations were considered to be able to cause yield loss (Sikora and Noel, 1991). By 2005, based on a more extensive survey, more than 70% of the SCN populations were able to attack PI 88788 and derived cultivars (Niblack et al., 2008). Growers with high SCN population densities in their fields are advised to rotate sources of SCN resistance, if possible, in order to reduce selection pressure (Niblack, 2005); however, little if any information is available on the long-term efficacy of this approach.

Nematicides also are an option for SCN management, and one or more are labeled for this purpose in most NCR states. But use of these pesticides costs $25 to $35 per acre, and there is little evidence that they consistently increase soybean yields sufficiently to pay for their use (Smith et al., 1991). Additionally, increases in SCN population densities can be measured in the fall following nematicide use at planting, which makes use of these compounds a recurring proposition and militates against their use unless other options have been exhausted. For the immediate future, use of nonhost crops and resistant soybean varieties will probably remain the most viable options for management of SCN.

Although there are some management options available, much work is needed to broaden and stabilize our management of this persistent, widespread, devastating soybean pathogen, particularly in light of its ready adaptation to resistant cultivars.

Corn-parasitic nematode management

Nematode management in corn historically has relied on at-planting application of soil insecticide-nematicides. Commercial resistance is nonexistent, and crop rotation strategies are complicated by the diversity of nematode species present in corn fields and the limited information available on species-specific host ranges. In the case of RLN, several species are known to parasitize both corn and soybean, making this common NCR rotation ineffective as a management option for controlling these nematode pests of corn.

Seed-treatment nematicides are a new option for managing corn-parasitic nematodes, with the first commercial products becoming available for the 2010-2011 growing seasons. These products provide fewer environmental concerns and promise greater benefit-cost ratios compared to traditional granular nematicides. Data to support grower recommendations currently is very limited, however, and it remains to be determined whether or not these new seed treatments will be effective and economical.

Decision-support database

Useful nematode management information for farmers in the NCR is available from a wide variety of sources, both public and private. Unfortunately, that information is also fragmentary and may be difficult to locate. For example, due to large SCN-resistant soybean cultivar evaluation programs in Iowa and Illinois, and smaller programs in other states, we have specific data about the actual levels of resistance in hundreds of soybean cultivars labeled as resistant by the companies who produce them. An effort to coordinate these programs and to simplify access to the data would be of tremendous value to soybean farmers. In addition, such coordinated efforts are of great value to researches because they highlight areas that are in need of concentrated, collaborative research. Our aim for this objective is to identify and coordinate a database or single source of information that will be of value to nematode management strategies in the NCR states.

Conclusions

The current and future threats to the economy of the NCR states represented by plant-pathogenic nematodes such as SCN and RLN require a collective approach - collective in the sense of comprising research and extension nematologists from each state, and in the sense of taking both fundamental and applied approaches to the research questions outlined in this proposal and giving our outreach responsibility the status of a separate objective. As a group, we have the expertise, collaborative relationships, and commitment required to address and achieve the objectives we have proposed.

Related, Current and Previous Work

There are many soybean cultivars with resistance to SCN on the market today with an average life span of two to three years. Most of the cultivars adapted to the NCR derive resistance from a common source, PI 88788. Almost every state in the North Central Region has a program to evaluate the performance of soybean cultivars using crop yield and quality measures. Members of NC1035 collaborate with agronomists to provide additional information in these trials about inoculum densities of SCN and response of SCN populations to resistant cultivars (Delheimer et al., 2010; Johnson et al., 2009). The most common source of resistance, PI 88788, was evaluated recently for performance against SCN populations across the region in an experiment coordinated through NC1035 (Faghihi et al., 2010). NC1035 members also collaborated to develop standard protocols for assessing soybean resistance to SCN in greenhouse tests (Niblack et al., 2009).

Populations of SCN have a high degree of genetic variability and can adapt to host resistance (Niblack et al., 2008). Virulence of populations on resistant varieties is an emerging concern so the NC1035 Committee began characterizing the virulence phenotypes of SCN within each state, adopting a common protocol for the assays (Niblack et al., 2002). In 2010, SCN populations from Illinois, Iowa, Kansas, Minnesota, Tennessee, Wisconsin, and Ontario were characterized for their virulence phenotype and the majority of the populations developed on the host differential PI88788 (NC1035 2010 Annual Report). This information serves as a critical resource to inform soybean breeders in the future utilization and deployment of resistance genes in the NCR.

Host resistance is the cornerstone for managing SCN, but cultural practices are also important for mitigating nematode damage in infested fields. Case studies from Indiana, discussed at annual meetings of NC1035, stimulated local studies on tillage in Minnesota (Chen, 2007), Iowa (Gavassoni et al., 2007), and Tennessee (Donald et al., 2009). Tennessee and Indiana assumed the lead on studying the importance of winter weed management for managing SCN (Creech et al., 2007; Donald et al., 2007) and taught other members of the group about the role weeds play in the persistence of SCN when its preferred host of soybean is unavailable.

Although SCN remains the most important nematode pest in the NC region, requests for nematode assays for corn rose significantly in 2010 across the region and the majority of the samples showed moderate to high population densities of Pratylenchus spp., root-lesion nematodes (NC1035 2010 Annual Report). A new nematode pest of corn was discovered in Tennessee (Bernard et al., 2007). Nematode pests of corn are extremely common, with incidence values approaching 100% of the fields in some states, so there is a need to establish dose/response relationships for implementing and evaluating nematode management strategies. Existing damage relationships for corn-parasitic nematodes were established decades ago (Norton and Hines, 1976; Smolik and Evenson, 1987; Todd, 1989; Todd and Oakley, 1996) and likely do not relate to modern corn hybrids or planting practices. In addition, damage threshold estimates for many species of corn-parasitic nematodes lack research support and thus a comparison of values used by diagnostic labs in the North Central region reveals a low level of consensus for most nematode genera. Largely because of limited funding, research on corn-parasitic nematodes has been neglected at a time when losses due to these pests have been predicted to increase due to reduced availability and use of soil nematicides and more intensive corn production. The development of new products for nematode control in corn has provided new opportunities and funding resources for renewing much needed research efforts in this area. Nematicidal seed treatments to manage SCN were tested throughout the region in 2008-2010 and the NC1035 committee met in June 2010 with industry representatives to discuss the role of nematode census data in pesticide efficacy studies. Data from independent experiments among participating states was examined collectively to identify ways to improve sampling and nematode assays and to aid interpretation of data from experiments conducted across multiple states.

Nematodes often are part of disease and pest complexes and the association of SCN with other pathogenic organisms has been studied by NC1035 participants. The interaction of SCN with soybean aphids was studied in Iowa (Avendano et al., 2007; Heeren et al., 2007) and Wisconsin (Hong et al., 2007). Concomitant infection of soybean by SCN and Pratylenchus spp. is common in the region, but has not been studied. The interaction of SCN with soil borne pathogens was studied in Iowa and Minnesota (Chen et. al., 2007; Sun et al., 2007). There appears to be site-specificity as to the strength of the association of SCN with other pathogens, but the consensus is that interactions may be the rule rather than the exception and that more work needs to be done.

Other regional nematology projects: There are three active regional nematode projects in addition to NC1035. These projects focus on cultural management of plant-parasitic nematodes and sustainable soil health (NE1040), improved diagnosis and management of plant-parasitic nematodes using modern diagnostic tools and host resistance, respectively (S1046), and genetic and biological variation in nematode populations (W2186). Some of the priorities and action plans developed by NC1035 are similar, in concept, to other regional technical committees but with a focus on different nematode pests and cropping systems. For example, identification of nematode species and races (S1046) and characterization of the genetic and biological variation in nematodes (W2186) are also needs with the NC region, but for a different suite of nematode taxa. The same could be said of host resistance (NE1040, S1046) with NC1035 placing focus on the SCN and corn nematodes different from those occurring in the South. Nematode genera vary in life history traits, survival strategies, and interactions with their host plant, so research to address the needs of growers in one region are not necessarily transferable to another. Soybean cultivars, cropping systems, and environmental conditions also vary significantly between regions.

Objectives

1. Develop, evaluate, improve, and integrate management techniques for plant-parasitic nematodes in the North Central Region to increase grower profitability.
   
2. Determine the relationships among nematode population characteristics, crop injury, and soil health.
   
3. Develop tools for technology transfer for management of regionally important nematodes, with special reference to SCN and corn-parasitic nematodes.
   

Methods

Objective 1. Develop, evaluate, improve and integrate management techniques for plant-parasitic nematodes in the North Central Region to increase grower profitability. A. Evaluation of SCN-resistant soybean lines and cultivars New soybean germplasm developed by NCR plant breeders will be screened for SCN resistance in participating states using standardized protocols (Niblack et al. 2009). Soybean lines with promising resistance from each state breeding program will be evaluated collectively across the region to increase the number of SCN screening populations and improve the characterization of each cultivars resistance. In addition, existing public and private company cultivars will be evaluated annually for resistance to the nematode in greenhouse and field trials. Soybean lines and cultivars will be screened under greenhouse conditions in Tennessee. Testing will consist of at least 7 replications per line and replications in time for lines nearing germplasm release. Each replication consists of an 8-cm-diameter steam-sterilized clay pot filled with a steam-sterilized potting soil mixture of 3 parts sand: 1 part silty loam field soil. Three seeds of each line are placed in a hollow in the soil after addition of 1 mL of H. glycines inoculum (2,500 to 4,000 eggs/mL). Additional sterilized potting is added to each pot. Water is added to pots as needed after 24 hrs. The greenhouse temperature is 27 C +/- 5 C. Supplemental lighting is used in the winter to provide a 14 hr light period. Indicator lines as specified for the HG Type Test are planted with each test. Approximately 35 days after inoculation, plant roots are removed from the pots. Pots containing the HG Type Test indicator lines have cysts forcibly removed from the roots with a strong stream of water. Cysts are collected on a 250-µm-pore diameter sieve and counted microscopically to confirm characterization of the inoculum. Soybean lines and cultivars for evaluation are rated visually once roots are removed from the pots for presence of cysts on the roots. The rating scale of 1 to 5 with 1 = 0-5 cysts, 2=6-10 cysts, 3=11-20 cysts, 4=21-40 cysts; 5=>40 cysts is used. All of the soybean cultivars entered in the Illinois and Kansas Soybean Variety Trials and identified by the producer (seed company) as resistant to SCN will be tested in the greenhouse for the actual levels of resistance to up to five different SCN populations according to a standard bioassay (Niblack et al., 2002). This work is supported by the Illinois Soybean Checkoff Program and the Kansas Soybean Commission, respectively. More than one hundred SCN-resistant soybean cultivars will be evaluated in field experiments in Iowa each year to assess the agronomic performance of the cultivars as well as their effect on population densities of the nematode. The SCN-resistant soybean cultivars, as well as widely grown susceptible soybean cultivars, will be grown in fields infested with the soybean cyst nematode in three separate locations in northern Iowa, three locations in central Iowa, and three locations in southern Iowa. Experiments will consist of four-row plots, each 17 feet long, from which data are collected from the center two rows. Each variety will be replicated four times in each experiment. Data to be collected from each plot will include population densities of soybean cyst nematode at the time of planting and again at harvest time, plant emergence four weeks after planting, plant height and lodging at the time of harvest, and grain yield (quantity, moisture content, and overall protein, oil, and fiber content). From 1990 until 2009, this work was self-supporting and fee-based. But starting in 2010, the project became fully supported by soybean checkoff funds from the Iowa Soybean Association. The addition of soybean checkoff funding has allowed the Iowa scientists to begin greenhouse evaluation of SCN resistance as well as the field evaluations described above. About 100 commercial and public cultivars and breeding lines also will be evaluated each year for their resistance to SCN populations in greenhouse and field trials in Minnesota. In Indiana, soybean cultivars will be evaluated on the basis of their particular sources of resistance. Although the focus will be on SCN resistance in soybean, several states will screen germplasm of other major crops for nematode resistance. Corn cultivars and/or breeding lines will be evaluated for their resistance or tolerance to RLN species in Minnesota, to RLN and lance nematode species in Iowa, and synthetic wheat cultivars will be evaluated for RLN resistance in Kansas. Deliverables from this work will include information on the resistance to SCN of soybean breeding lines and germplasm being used by public soybean breeders throughout the NCR. The proposed work also will generate and disseminate information about the agronomic performance and nematode management offered by commercial resistant soybean cultivars available to growers in the North Central Region of the United States. B. Assessment of HG Types and other aspects of virulence To obtain information about the virulence characteristics of the SCN populations that are present in the NCR, participants from Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Tennessee, Wisconsin, and Ontario, Canada, will annually monitor the SCN populations from their states. An HG type test (a replacement for the SCN race test) will be conducted as described by Niblack et al. (2002) on each nematode population collected. A statewide survey of the frequency and distribution of virulence phenotypes will be conducted every five years in Minnesota. In Wisconsin, the Soybean Marketing Board sponsors four free SCN soil assays per grower annually. These samples are processed by the Plant Pathology Disease Clinic and samples positive for SCN are sent to the MacGuidwin lab. For one positive sample per grower, the SCN population will be increased on a susceptible soybean cultivar. Eggs will be harvested after approximately 50 days and the Hg Type of the population will be determined using methodology detailed in Niblack et al, 2002. Cysts from each population will be stored in sand at 10 C for future work. Cysts from over 100 Wisconsin populations of SCN characterized for their virulence phenotype are now in storage and available by request. Field experiments have been established in Minnesota to determine selection pressure of various rotations of soybean resistance sources and nonhost crop on SCN virulence phenotypes. In Kansas, changes in SCN virulence frequencies will be monitored in replicated plots of the major resistance sources (PI 548402, PI 88788, and PI 437654) and representative examples of commercial cultivars derived from each. The deliverable that will be generated from this work will be information about the virulence characteristics of SCN populations that occur throughout the NCR. This information will be vital to guide soybean breeding efforts. C. Evaluation of new nematicidal seed treatments for management of SCN and corn-parasitic nematodes Nematicidal seed treatments for corn and soybean will be evaluated in replicated growth chamber, greenhouse and field trials in Illinois, Indiana, Iowa, Kansas, Wisconsin, and Ontario, Canada. Field plots will be established in sandy or silt loam soils with damaging levels of SCN or corn-parasitic species such as RLN. Treatments will be arranged in a completely randomized or randomized complete block design with a minimum of four replications. Nematode populations will be extracted from root and soil samples collected 4-6 weeks after plant emergence using standard sampling and extraction protocols. Greenhouse and growth chamber studies will be conducted in inoculated soil, with measurements taken 30 days after plant emergence. Additionally, yield and nematode data from strip-trial comparisons of seed-treatment nematicides in growers fields will be collected from across the region and subjected to meta-analysis. This research will provide important information to NCR growers about the efficacy of new nematode control products across the diverse environmental conditions and management practices of the region. D. Evaluation of rotational crops and cultural practices for SCN and corn-parasitic nematode management The dominant cropping system within the NCR is corn-soybean rotation. Previous studies in this region have demonstrated that a single year of a nonhost crop (corn) has had variable effects on SCN population densities (Donald et al., 2006). The identification of alternative cropping systems that maintain overall productivity and also suppress SCN would provide substantial economic benefits to the region. One possible method to suppress or eliminate SCN from fields is to modify soil by improving the biological and soil physical qualities with soil amendments. The proposed project will foster the continuation of ongoing cropping systems research in the NCR. In Indiana, a two-year study of the effect of annual rye grass on SCN soil populations will be continued. The effects of soybean germplasm and corn-soybean rotation under till and no-till practices on Heterodera glycines population dynamics will be studied using artificially inoculated field plots within the quarantined experimental site at Michigan State University. Nematode population dynamics and agronomic data will be collected at intervals during the growing season (Melakeberhan, 2007). Field experiments will be conducted to determine crop sequence, tillage, and soil fertility management effects on SCN and corn-parasitic nematodes in Minnesota. Studies of RLN species occurring in rotations common to potato production will be conducted in Wisconsin. Cover crops compatible with potato cropping systems include plants in the Brassicaceae family, rye, winter wheat, and forage pearl millet if short season processing vegetables such as pea and snap bean are grown. Several field studies in 2011 will follow RLN populations over time with the goal of determining how residues from the previous crop influence the rates of infection and reproduction on the living current crop. The effects of amending field crops production soils with organic and inorganic nutrient sources on parasitic variability and reproduction potential of populations of H. glycines and/or Meloidogyne hapla (Melakeberhan et al., 2007; Mennan and Melakeberhan, 2010), and nematode community structure (Bongers and Ferris, 1999; Ferris et al., 2004; Neher and Campbell, 1996; Yeates, 1994; Yeates et al., 1993) will be investigated in Michigan. Integrated efficiency of amendment use will be determined as previously described (Melakeberhan, 2006; Melakeberhan and Avendano, 2008). The long-term goal is to develop soil amendment practices that suppress parasitic nematode population density and improve beneficial nematodes, soil conditions, plant growth and yield with flexibility of incorporating management of additional yield-limiting factors, leading to economically and ecologically integrated applications. As a deliverable, this research will provide information on the effects of numerous, diverse cropping systems on population densities of the SCN and RLN in fields throughout the NCR. E. Investigation of pest interactions involving plant-parasitic nematodes and their contribution to yield losses in North Central Region crops There is increasing awareness that above- and below-ground biota interact through their multiple effects on shared host plants (Wardle et al., 2004). Besides SCN, soybean fields also are damaged by other plant-parasitic nematodes, fungal and bacterial diseases, weeds, and insect herbivores, which affect yield negatively. SCN severely stunts roots of infected plants, leading to reduced ability of the plant to take up water and nutrients from the soil, in essence creating drought and nutrition-deficiency stress, even in soils with adequate water and minerals available (Koenning & Barker 1995). This weakening effect of the host plant will likely have an effect on other soybean pests resulting in interaction effects. Evidence also suggests that SCN is a passive vector of root diseases such as SDS (Donald et al., 1993; Gao et al., 2004). The interactions of M. phaseolina (causal agent of charcoal rot), F. virguiliforme (causal agent of SDS), and H. glycines (SCN) will be investigated in factorial greenhouse and field microplot experiments in Kansas. Fungal CFUs and nematode cysts and eggs will be counted per gram of root tissue and per unit length of root. In addition, flowering sites, pod number, seeds per pod, and pods per plant harvest data will be collected. SCN-SDS relationships also will be studied in greenhouse and field experiments in Indiana. The population dynamics and interaction of a generalist species, Pratylenchus penetrans, and a specialist species, Heterodera glycines, will be studied on their common soybean host in corn-soybean rotations in Wisconsin. The primary emphasis of this project will be to determine the role of soybean genotype on the nematode interaction. The deliverable for these experiments will be research-based information on the interactions of the soybean cyst nematode with other soybean pests that commonly occur throughout the NCR and information on how these negative interactions might be effectively managed with available SCN-resistant soybean cultivars. Objective 2. Determine the relationships among nematode population characteristics, crop injury, and soil health. A. Develop a list of damaging nematodes for corn and other major crops in the North Central Region Preliminary surveys of the diversity of corn-parasitic nematodes in the NCR recently have been conducted in several states and the results indicate that potentially damaging populations are widespread. In Illinois, for instance, a random survey revealed that 63% of the corn fields are infested with RLN species at population densities that are higher than the economic injury thresholds established in the 1970s. At least seven species of RLN were represented, several of which (such as P. scribneri and P. penetrans) are known corn pathogens. Other frequently-occurring nematode parasites (and potential pathogens) of corn were spiral nematodes (mostly Helicotylenchus spp.) at 99% frequency, stunt nematodes (several genera and species) at 37% frequency, and lance nematodes (Hoplolaimus spp.) at 22% frequency. More than 450 corn samples were processed in Indiana in 2010 and additional corn fields will be sampled throughout the proposed project. Random surveys also will be conducted in Kansas, Minnesota, and Wisconsin. The resulting information will be summarized for the region and used to rank corn-parasitic nematodes in order of importance. B. Determine damage thresholds for major corn-parasitic nematode species Information on the potential for yield loss in corn for most nematode species is either absent or several decades old and based on single species and also for hybrids that were considerably different from those being grown today. Because of the recent marketing of corn nematode management products, it is critical that we develop robust host-nematode (species + population density) equations to support management recommendations. The Macguidwin lab in Wisconsin is developing dose/response relationships for Pratylenchus spp. (emphasis on P. penetrans) on corn and soybean using endemic field populations with an aggregated distribution for data collection. Sites are selected before crop emergence and flagged for repeated sampling during the growing season and collecting yield. Similar field and greenhouse experiments will be conducted in Illinois, Indiana, Kansas, and Minnesota to identify damage thresholds for the major corn-parasitic nematode species in those states. The data from these experiments will be used to develop predictive models for yield loss in corn that will form the basis for regional yield loss estimates. C. Characterize infraspecific variation in host-parasite interactions across the North Central Region The MacGuidwin lab maintains a collection of Pratylenchus penetrans isolates from Wisconsin cultured on corn root explants and has agreed to establish cultures of other RLN species collected from the NCR for distribution to participating states. This collection will provide an important resource for characterizing variation in pathogenicity, host range, and reproductive/survival potentials among isolates both within and between species. D. Develop predictive models of nematode population dynamics for SCN and other regionally-important plant-parasitic nematodes Among other things, seasonal nematode population dynamics is a function of the host, soil conditions and management practices in the prevailing environments. A combination of the recently developed daily nematode population density (DNPD) and fertilizer use efficiency (FUE) models (Melakeberhan and Avendano, 2008) will be used to determine the seasonal relationships amongst selected nematode species and/or populations in Michigan. Nematode population density (NPD) is the total of all stages of a given nematode per 100 cm3 of soil plus per g fresh root. DNPD, a new approach and an indicator of nematode damage functions and host carrying capacity over the growing season, is calculated as follows: DNPD = (NPD / the number of days from planting to last sampling date). DNPD will then be used to test for correlations with changes in plant growth parameters and yield, a step towards developing measurable nematode threshold levels over a growing season rather than at one point in time. FUE, defined as increase in host productivity and/or decrease in nematode population density in response to a given fertilizer treatment, provides proof-of-concept for testing for integrated agronomic, biological, economic, environmental and yield-limiting factor suppression efficiency of management strategies. E. Identify sampling and extraction issues related to management of economically important plant-parasitic nematodes in the region Population dynamics studies will be conducted in Wisconsin to identify the optimal time for sampling to predict yield loss of corn and soybean due to P. penetrans, and for studying the survival of Pratylenchus spp. in dead root fragments. These fragments currently are not included in the assays conducted by many labs, and their significance for infection and population increase needs to be investigated. Studies will be conducted in Kansas and Indiana to identify similar issues related to the sampling and extraction of economically important plant-parasitic nematodes in the region. Objective 3. Develop tools for technology transfer for management of regionally important nematodes with special reference to soybean cyst nematode and corn parasitic nematodes. A. Assemble a dynamic database of soybean cultivar characteristics related to SCN resistance The rationale for this database is that there is no single coordinated source of such comprehensive information currently available. This database will incorporate and expand upon currently available databases and include, among other things, evaluations from objective 1A, industry assessments, and sources of SCN resistance and other defensive traits. Our procedures will be as follows: a). All participants will solicit information from local seed companies in their states to learn: i) the names of all SCN-resistant varieties they handle; ii) maturity groups for these varieties; iii) the source of resistance for each variety; iv) agronomic traits of special interest; v) other traits of interest such as resistance to other pests and diseases. b). Each participant will obtain seeds from the local seed companies in the state and screen these cultivars against several SCN isolates and different races or HG types; and report their findings to be included in the data base under their names. c). Request permission from owners of presently available pertinent databases to share their information on our website along with the data we have accumulated. d). Maintain this database in a central location  in the SCN section of www.planthealth.info - and possibly on our own NCR Nematode website. B. Provide reliable information on the distribution of virulence phenotypes for SCN populations in the North Central Region Survey results from participating states (objective 1B) will be collected and compiled for dissemination on www.planthealth.info and on the NCR Nematode website. Characterization of the SCN population is crucial to soybean breeders in the NCR and will inform future breeding efforts for SCN resistance in the region. Specifically, this information will allow breeders to select the most appropriate resistance sources to deploy across the region. Continued use of PI 88788 as the primary source of resistance would not be wise, for instance, if the majority of SCN population in the NCR can reproduce on this source. C. Provide readily accessible and reliable information on rapidly evolving nematode management strategies such as the new commercial seed treatments for nematode control Results of seed treatment trials conducted by nematologists across the NCR (objective 1C) will be summarized and made available on www.planthealth.info and the NCR website. Extensive independent evaluation of new control products will provide growers in the region with reliable information upon which to base management decisions. D. Provide a consensus damage threshold for each of the major corn-parasitic nematodes in the NCR Data from experiments conducted for objective 2B will be summarized and used to develop research-based damage thresholds. The elimination of discrepancies among existing damage threshold values will vastly improve the management of corn-parasitic nematodes in the region.

Measurement of Progress and Results

Outputs

• A coordinated list of soybean cultivar characteristics related to SCN resistance.
• A coordinated region-wide survey of HG Types.
• Improved damage thresholds for nematodes on corn and other major NCR crops.
• A database of the performance of new commercial products for nematode control.
• Predictive models of SCN and RLN population dynamics under field conditions.

Outcomes or Projected Impacts

• Testing and disseminating unbiased information on the actual resistance levels of "SCN-resistant" soybean cultivars will result in a sustained increase in soybean production and profitability of soybeans grown in SCN-infested environments.
• Information on the frequency and distribution of HG Types will enable soybean breeders to make informed choices on the use of resistance sources in breeding programs. More effective sources of resistance will increase production and profitability of soybeans grown in SCN-infested environments.
• Current damage threshold estimates for plant-parasitic nematodes that feed on corn often are poorly supported by research data. Better estimates will form the basis for improving management recommendations and allow growers in the north central region to make decisions on whether to pay for additional crop inputs (nematode seed treatments) based on accurate and current information.
• Information on the efficacy of several new nematode control products currently is limited. As with cultivar resistance, testing and disseminating unbiased information on product performance will increase production and profitability of corn and soybeans in the NCR.
• Development and validation of life history models for SCN and the major RLN species in the region will enable us to account for some of the variability we see in results from field experiments with SCN and improve management recommendations.

Milestones

(2012): Objective 1: Identification of coordinators for each sub-objective; design, coordination and implementation of collaborative experiments for each sub-objective. Objective coordinators will seek funding from extramural sources. Some funding already is in place in the form of a new grant (March 1, 2011 to February 28, 2014) from the North Central Soybean Research Program to evaluate effects of nematode seed treatments on soybean cyst nematode reproduction and soybean yields throughout the NCR. Objective 2: Identification of coordinators for each sub-objective; design, coordination and implementation of collaborative experiments for each sub-objective. Objective coordinators will seek funding from extramural sources. Objective 3: Design of database and web site for access and collection of relevant databases currently available in different locations; publication of the first year of annually-collected databases (objectives 1A, 1B, and 1C).

(2013): Objective 1: Second year of field and greenhouse experiments conducted. Objective 2: Second year of field and greenhouse experiments conducted. Objective 3: Completion of web site development and publication of the second year of annually-collected databases (objectives 1A, 1B, and 1C).

(2014): Objective 1: Third year of field and greenhouse experiments conducted. Objective 2: Third year of field and greenhouse experiments conducted. Objective 3: Publication of the third year of annually-collected databases (objectives 1A, 1B, and 1C).

(2015): Objective 1: Fourth year of field and greenhouse experiments conducted. Objective 2: Fourth year of field and greenhouse experiments conducted. Objective 3: Publication of the fourth year of annually-collected databases (objectives 1A, 1B, and 1C).

(2016): Objective 1: Generation of refereed journal publications based on results from 4 years of experiments for each sub-objective; assessment of each sub-objective and development of proposals for continuing research. Objective 2: Generation of refereed journal publications based on results from 4 years of experiments for each sub-objective; assessment of each sub-objective and development of proposals for continuing research. Objective 3: Publication of the fifth year of annually-collected databases (objectives 1A, 1B, and 1C).

Projected Participation

View Appendix E: Participation

Outreach Plan

Our audiences include farmers, commodity groups (such as soybean growers' associations), agribusinesses from small consulting firms to large seed companies, regulatory agencies, and scientists in industry, extension, and academia (Table 1). We will tailor our outreach to the most appropriate audience. For example, the SCN-resistant soybean cultivar information will be of greatest use and interest to farmers and agribusinesses. In some individual states/provinces, this information will be disseminated in hard-copy form, published and disseminated by commodity groups. Our plan is to combine all the similar databases from each area into one relevant to the entire region, and offer public access through the internet at www.planthealth.info. Individual states/provinces will publish applied research results annually through extension outlets, including traditional extension publications, bulletins and newsletters, and web sites. Again, these reports will be gathered for region-wide public access via the internet (www.planthealth.info). Information generated through the fundamental research (objective 2, for example) will be disseminated through refereed research outlets such as the Journal of Nematology, Phytopathology, and other scientific publications. Specific outreach goals are detailed in the timelines.

Organization/Governance

We will be using the standard form of governance.

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Attachments

Land Grant Participating States/Institutions

AR, IA, IL, IN, KS, MI, MN, MO, ND, OH, WI

Non Land Grant Participating States/Institutions

Tennessee