Duration: 10/01/2006 to 09/30/2011

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. All of these crops are susceptible to highly virulent and invasive plant-parasitic nematodes. Fortunately, the soybean cyst nematode (SCN), Heterodera glycines, is the only one widely distributed through the region. SCN is 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.

In addition, SCN is widely considered to be a classic example of an invasive species and therefore a good model for studying the fundamental dynamics of invasive species to avoid major detrimental economic effects from other nematode pests not yet of major significance in our region. Examples of such pests include nematodes such as the corn cyst nematode, cereal cyst nematode, potato cyst nematode, potato rot nematode, and Columbia root-knot nematode, which are not established throughout the NCR, but which have the potential to do so: they are established in surrounding regions. It is imperative, therefore, for us to understand the fundamentals of invasion biology as exemplified by SCN.

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) To develop, evaluate, improve and integrate management techniques for soybean cyst nematode in the NCR to increase grower profitability;

2) To better understand and apply the concepts of invasion biology as revealed by SCN epidemiology;

3) To develop a decision-support database for management of SCN and other regionally important 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, VIPS). 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 strong, i.e., able to cause yield loss (Sikora and Noel, 1991). By 2005, based on a more extensive survey, more than 85% of the SCN populations were able to attack PI 88788 and derived cultivars (Niblack, unpublished). 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.

SCN as a model for invasion biology

Severe nematode pathogens of corn and small grains, and soybean pathogens other than SCN, occur elsewhere in the United States and have yet to become well established and of major significance in the NCR states. These nematodes may affect important crops directly, and also indirectly through interactions with other pathogens, as does SCN. Their appearance may also have economic consequences due to phytosanitary regulations and the trade restrictions placed on localities known to sustain populations of regulated nematode species. A current example is the detection of infestations of a potato cyst nematode (Globodera pallida) in Idaho; the consequences of this invasion by a quarantined pathogen are yet to be determined as of this writing (2006). It is imperative, therefore, for us to understand the fundamentals of invasion biology in relation to SCN and other nematodes that have major detrimental economic potential as invasive species.

SCN is a classic example of an invasive species. In the United States, SCN is an exotic. Its origin is suspected to be northern China, where it had been observed for 50 years prior to its first known appearance in the US. SCN was first reported in North Carolina in 1954. During the following three years, it was reported from Tennessee, Arkansas, Kentucky, Mississippi and Missouri (Riggs, 2004) and was the object of a federal quarantine until the early 1970s. Being easily transported by any means capable of moving soil, this major plant pathogen is now well established in 39 states, including every state of the NCR.

Rapid spread of SCN can be attributed to a number of invasive characteristics: relatively short age to first reproduction, high fecundity, dispersal ability, and capacity to survive drying in the protective cyst stage. Like many invasive species, SCN most likely escaped specialized predators and parasites during its initial establishment in North America. The rapid expansion of soybean production in the US was accompanied by management practices that facilitated the spread of this pathogen by moving soil and seed across broad geographic regions.

In this regional research project, SCN will be used as a model system for development of the principles of invasion biology of soil-borne pathogens and soil invertebrates in general (Shea and Chesson, 2002). This knowledge will be used to develop new and innovative practices to both minimize losses caused by SCN and decrease risk to other invasive species that are not currently of significance in the region.

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 screening programs in Iowa and Illinois, and smaller programs in other states, we have access to 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 databases 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 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

A search of the Multistate Regional Project CRIS database identified 17 active projects involving plant-parasitic nematodes. There is little or no overlap between this proposed project and those outside the region because the crops and/or nematodes addressed are different. The projects reviewed focused on nematode genetic variability (W-1186), sustainable management practices (NE-1019, MICL 01792, MICL 02095, SD-00144H, WNP-00564), soil suppressiveness (CA-R*-NEM-5811-H, CA-R*-PPA-7444-CG, IND-055075, IND-055075G, ), soil amendments for nematode control (ARS-1275), soil community structure (VT-H01206MS), plant resistance to SCN and/or root-knot nematodes (S-1015, CA-D*NEM-5205-H, GEO 00905, IND 058020A), and molecular methods for nematode identification (NEB-21-075). Eleven of those projects involve the NCR states, with 9 involving participants of this group. Projects IND055075 and IND055075G (CSREES IND) are independent from this group and propose the study of nematode suppressive soils in Indiana, which will complement the research we propose and may set the stage for future collaborations.

A search for nematodes as invasive species identified three projects, all outside the NCR. Project 1275-22000-200-00D (ARS 1275) refers to methods used to identify a new root knot nematode found in Florida peaches, presumably introduced into the US recently, and considered a potential invasive species. The research proposed in project CA-R*-NEM-7394-H (CSREES CALB) will contribute significantly to the development of diagnostic tools for phytoparasitic nematodes in California, increasing the ability of growers to accurately assess yield loss risks and thereby make better management decisions, especially in the face of dwindling means of chemical control and successive introductions of invasive species. Project CA-R*-NEM-5811-H (CSREES CALB) is the only one that addresses cyst nematodes as invasive species. It proposes the identification of potential biocontrol organisms associated with cyst nematodes, and testing conducive and suppressive soils in California to develop a plan to prevent the introduction of cyst nematodes in the state. The understanding of the properties that make the soybean cyst nematode such a successful invasive species gained from the research we propose will be of great value to places like California where SCN has not been detected.

Members of our group have conducted cooperative research in the past (NC-215 project). In conjunction with annual meetings, we conducted workshops at the close of the business meeting for 4 years. These workshops were:

Cyst Nematode Identification Workshop, 2000

Dorylaimida Workshop, 2001

Standardization of Procedures for Extraction of Soybean Cyst Nematode, 2002

Identification of Free Living Nematodes, 2003.

Identification and Ecology of Soil Arthropods and Protozoa, 2004.

Objectives

1. To develop, evaluate, improve and integrate management techniques for soybean cyst nematode in the NC region to increase grower profitability.
   
2. To apply the concepts of invasion biology to SCN epidemiology.
   
3. To develop a decision-support database for management of SCN and other regionally important nematodes.
   

Methods

In order to effectively address the current and potential detrimental consequences of plant-pathogenic nematodes in the NCR, we developed a set of experiments and activities designed to address each objective. These are described below, following restatement of the overall objectives. Objective 1: Develop, evaluate, improve and integrate management techniques for soybean cyst nematode in the NC region to increase grower profitability. The focus of the research is maximizing soybean yields and/or minimizing reproduction of the nematode. A. Evaluation of SCN-resistant soybean lines and cultivars Nematologists in Kansas, Illinois, Indiana, Iowa, Michigan, Minnesota, Wisconsin, and Ontario, Canada, will participate each in field and/or greenhouse evaluations of new soybean germplasm developed for the plant breeders in the region. This activity will be administered by the University of Illinois, and the soybean lines to be evaluated include maturity groups 0, 1, 2, 3, and 4. Even though the testing methodologies may vary among participating laboratories, the data generated will be crucial to soybean breeders and are the only sources of SCN evaluation to the plant breeders. Results of these experiments will be published yearly in the Northern Regional Soybean Cyst Nematode Test Report by the United Soybean Board. In addition to the work described above, in Iowa each year, more than one hundred soybean cyst nematode-resistant soybean cultivars will be evaluated in field experiments to assess the agronomic performance of the cultivars as well as their effect on population densities of the nematode. The soybean 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). This work is self-supporting and fee-based. In Illinois each year, all of the soybean cultivars entered in the Illinois Soybean Variety Trial and identified by the producer (seed company) as resistant to SCN will be tested in the greenhouse for the actual levels of resistance to five different SCN populations according to a standard bioassay (Niblack et al., 2002) with ten known susceptible cultivars as checks. This work is supported by the Illinois Soybean Checkoff Program. In addition, the Michigan Soybean Promotion Board will annually support four field-scale SCN resistant variety evaluation trials. Data from this research will be an integral part of the project. 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 SCN population 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, Wisconsin, and Ontario, Canada, will annually collect several SCN populations from their states. An HG type test (a replacement for the soybean cyst nematode race test) will be conducted on each nematode population as described by Niblack et al. (2002). Two long-term field trials will be conducted in Michigan to assess the dynamics of HG Type virulence, sponsored by the Michigan Soybean Promotion Board. A long-term field trial will be conducted in Minnesota to test the effects of rotation of sources of resistance. 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 soil amendments for management of SCN A possible method to suppress or eliminate SCN from fields is to modify soil by improving the biological and soil physical qualities with soil amendments. Research in this area has been ongoing for green manures, nonhost cropping systems, and recycled composted materials (such as leaf and grass waste, recycled sewage sludge, and organic materials such as plant byproducts). In the proposed project, researchers in Iowa, Michigan, Minnesota, and Ontario, Canada, will assess the effects of specific soil amendments on SCN population densities and soybean yield in nematode-infested fields. The soil amendments that will be examined include composted municipal sewage sludge, composted yard waste, swine manure, and composted plant material. These soil amendments will be applied at various rates to replicated, four-row plots of soybeans in which resistant and susceptible soybean cultivars will be grown. The data will be collected from the center two rows of each plot. Soil samples will be collected at planting and at harvest, and SCN population densities will be assessed in each soil sample. Additional soil samples may be collected at other times during the growing season as time and financial resources permit to get additional information about nematode population dynamics. Plant data to be collected from each plot will include emergence one month after planting and plant height, lodging, and yield at harvest. Two long-term trials will be conducted in Michigan to develop procedures for soil quality renovation in relation to alleviation of SCN as a key pathogen. Both trials include an integration of soil amendments, crop rotation, cover crops and SCN resistant varieties. The project will be supported by the Michigan Soybean Promotion Board. The deliverable of the proposed work will be information on SCN population density changes and soybean growth and yield in infested fields that are treated with the tested soil amendments. D. Evaluation of SCN nonhost crops 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. The effects of several cropping systems on population densities of SCN and associated nematodes will be measured in experiments that will be conducted in Illinois, Indiana, Kansas, Michigan, Minnesota, South Dakota, Wisconsin, and Ontario, Canada. Experiments will assess the nematode population densities in rotated and continually cropped systems. Alfalfa, canola, corn, Illinois bundleflower, pea, sorghum, sunn hemp, SCN-resistant and susceptible soybean cultivars, and wheat will be included among the various cropping systems, and cultural practices will include no-till, conventional, and minimum till. Trap crops are commonly used in Michigan for control of the sugar beet cyst nematode; a Michigan research project will include potential trap crops for SCN. As a deliverable, this research will provide information on the effects of numerous, diverse cropping systems on population densities of the SCN and other nematodes in fields throughout the NCR. E. Pest interactions 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). Growth-chamber and field research will be conducted in Illinois and Iowa to determine how SCN and soybean aphid, Aphis glycines, affect development and reproduction of each other on soybean, how the interaction of the two pests affects soybean yield losses, and whether management recommendations for the soybean aphid and the SCN need to be altered based on the interaction of the two pests. The growth chamber experiments will provide insight into how the nematode and aphid affect reproduction of each other after a period of one to two months under controlled conditions on soybean cultivars that are susceptible and resistant to the nematode. Field microplot research, in which soybeans are grown in small, circular or rectangular plots and then infected with SCN and infested with soybean aphids, will be conducted to assess the effects of the nematode and aphid interactions on reproduction of the pests and growth, development, and yield of the soybeans. In Illinois, Indiana, Iowa, Minnesota, South Dakota, Wisconsin, and Ontario, Canada, observations will be made of the presence and population densities or disease levels of insect herbivores, other plant-parasitic nematodes, weeds, and fungal diseases, such as Asian soybean rust, soybean sudden death syndrome, and root rots in experiments conducted in fields infested or noninfested with the SCN. In some experiments, both susceptible and soybean cyst nematode-resistant soybean cultivars will be included to determine if existing nematode resistance can be used to mitigate any negative interactions that are detected. To complement these field experiments, some states also will conduct greenhouse experiments in which soybean plants infected or noninfected with the soybean cyst nematode are exposed to other soybean pests and pathogens to assess the effect of parasitism by the nematode on the biology and population dynamics of the other soybean pests. Pratylenchus penetrans, a lesion nematode species, is the most common phytopathogenic nematode species in Michigan. Interactions between this species, SCN and SCN resistance sources will be evaluated. 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: Apply the concepts of invasion biology to SCN epidemiology. The key concepts of invasion biology will be used to identify habitat properties that increase risk to soybean production from SCN, and integrate these findings into a conceptual model for economically viable corn, soybean, small grain and potato production systems for NCR agriculture. The following methodology is designed to develop and validate a protocol for identification of agricultural habitats that are conducive for successful colonization by invasive soil-borne invertebrate species. The procedure consists of four tiers of coordinated multi-state activities. Tier 1 Protocol (Initial assessment of habitats for occurrence of SCN). Each participating State or Province will collect soil samples from a variety of commercial soybean sites. Each site will be geographically positioned (GPS). The samples will be processed for SCN and the associated population densities determined. Each site will be classified in one of the following four categories: 0) no SCN detected, 1) low SCN (1-1000/100cm3), 2) moderate SCN (1000-10,000/100cm3) and 4) high SCN (>10,000/100cm3). Sample sites may be from different fields or from a gradient within an individual field. Tier 2 Protocol (Habitat conduciveness evaluation) Soil from each site where SCN was not detected will be placed in 250 cm3 conetainers and inoculated with 500 second-stage juveniles of SCN /100cm3 soil. A previously germinated SCN susceptible soybean seedling will be transplanted into each conetainer and maintained under greenhouse conditions for 30 days. At the end of the experimental period, the soil will be processed for SCN and the associated population densities determined. Each site will be classified in one of the following four categories: 0) no SCN detected, 1) low reproductive potential (1-10 females /100cm3), 2) moderate reproductive potential (10-100 females/plant and 4) high reproductive potential (>100 females per plant). Two hundred sites throughout the region will be identified for further investigation. These will be identified by randomly selecting five sites in each of the four categories from each of the ten participating states. Tier 3 Protocol (Associated soil quality assessment) The participating scientists will return to the 200 previously selected and GPS marked sites for collection of a second set of soil samples. Ten metrics (types of soil analyses) will be run for each of the 200 samples. These will include soil pH, electrical conductivity, organic matter, texture, water aggregate stability, microbial functional groups including fungal and bacterial parasites of SCN, PPI (Plant Parasitic Nematode Index), MI (nematode Maturity Index), SCN population density, EEA (Extracellular Enzyme Activity) and metagenomics. Data from these metrics will be evaluated using multivariate statistics and randomization-bootstrapping techniques to discern patterns associated with invasive characteristics of the habitats. This will be used to generate hypotheses about the soil characteristics most suitable and most predictable for invasion by SCN or other soil invertebrates. A conceptual model for invasive biology of soil invertebrates: with special reference to SCN will be developed. Tier 4 Protocol (Invasive biology model validation) The conceptual model for invasive biology of soil invertebrates will be validated using an independent data set. This will be done through the use of a new set of 200 geo-positioned soil samples. The exact procedure for selecting these samples is yet to be determined. The Tier 1 and Tier 2 Protocols, however, will be done in reverse order. This means that the nine metrics will be determined for each sample and used to classify each soil one of four categories of habitat risk to invasion. The sites will then be re-sampled and the soil used for the Tier 1 Protocol Analysis to verify its conduciveness to rapid colonization by SCN, followed by exponential growth of the population. Objective 3: Develop a decision-support database for management of SCN and other regionally important nematodes. A. We will assemble a dynamic database of soybean cultivar characteristics related to SCN resistance. The rationale for this 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 1, 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 on our own North Central Regional Soybean Nematode website, and create a new database accessible to all. B. Develop standard operating procedures (SOP) for screening SCN resistant lines in cooperation with industry. The identification of SCN virulent populations was developed in order to more accurately identify the many different SCN virulent bio-types (Riggs and Schmitt, 1888; Niblack et al, 2002). The more recently accepted HG classification scheme is useful for describing SCN variability. Characterization of the SCN population is important in selecting the soybean variety which will perform best in a particular field. From this information, growers can choose soybean varieties which have a source of resistance to that particular population, i.e. it would not be appropriate to select a variety whose sole source of resistance is PI 88788 if the SCN population tested can reproduce on PI 888788. (Niblack, T.L. and Riggs, R.D., 2004). Procedural steps for screening resistance in soybean cultivars have been published but private and public labs have adapted and or modified the published techniques. (Niblack et al., 2002. Riggs and Schmitt,1988). The impact of modifications to the testing protocol has not been explored however, research data has shown that modifications to the temperature under which conditions were conducted affect the race outcome (Colgrove, et al. 2002). Standard Operating Procedures (SOP) for screening soybean varieties reaction to SCN populations do not currently exist. Uniform standard operating procedures have not been developed for private and public screening programs. Variability among testing locations lead to several problems, the most important would be the inconsistent response of new cultivars to similar populations of SCN that lead to varieties with misleading resistance response descriptions. The variability among test protocols hinders establishment of quality control/quality assurance that soybean producers require. a) We will verify SOP across public and private labs to formulate standardized methods. b) We will host a workshop(s) to educate private and public labs on methods that are accepted as SOP's. c) We will establish a web site describing best practices for extraction practices for SCN eggs, and publish SOPs in referred journals and/or general information bulletins. C. Consolidate and validate existing information on SCN generation time in the field based on degree-day accumulation across the region. The rationale for this is as follows: Under laboratory conditions, SCN matures in 28 days (Lauritis et al., 1983) at 75 F and management decisions have been based on this assumption. Greenhouse studies also showed that SCN is inactive below 50 F and we have assumed this to be true under field conditions as well (although it may not be true in all parts of the NC region). Such information provides a benchmark for evaluation of cultural control tactics that include e.g., the selection of planting dates and assessments of the likely effects of SCN susceptible winter annual weeds. Field data regarding the validity of these assumptions do not currently exist for the widely differing growing areas of the North Central region. We anticipate participation by all NC states. Our procedures will be as follows: a). Soybean plants will be planted in the spring in naturally infested sites throughout the region when soil T is appropriate for the particular area (e.g., the soil T reaches and holds at 50 degrees). b). A model predicting generation time based on degree-day accumulation (50 F basal temperature) will be used to schedule sampling for observation of adult females. Accumulation of degree-days begins at planting because SCN is an obligate parasite. c). Two weeks post germination each participant will begin to monitor the development of female nematodes by destructive sampling. d) After the accumulation of 500 degree-days, each participant will begin to sample every 50 degree-days (= 5 days at 60 F soil T) to watch for the appearance of first females. e) Compare data obtained throughout the NCR and refine model. D. Generate a checklist of key biotic and abiotic factors associated with, and predictive of, increased/decreased risk of SCN establishment, survival, and spread. This information also will be useful in evaluating the nematodes potential to reach damaging population densities in areas already invaded. The rationale for such a database arises from the fact that much has been written about how SCN is spread, but little is known about the conditions, beyond the presence of a suitable host, that favor the nematodes introduction into a given habitat and its subsequent development as an economic pest. Our procedure will be to incorporate the information developed and validated in Objective 2 into the North Central Regional Soybean Nematode web site along with recommendations for best management practices known to promote those conditions determined to be antagonistic to SCN (e.g. if low organic matter is an important risk factor for SCN invasion, this risk could be managed through conservation tillage).

Measurement of Progress and Results

Outputs

• A database of soybean cultivar characteristics related to SCN resistance.
• Protocol for best practices for screening soybean for resistance to SCN.
• A predictive model of SCN population dynamics under field conditions.
• A checklist of key biotic and abiotic factors associated with, and predictive of, increased/decreased risk of SCN establishment, survival, and spread.

Outcomes or Projected Impacts

• Testing and disseminating unbiased information on the actual resistance levels of "SCN-resistant" soybean cultivars will result in increased production and profitability of soybeans grown in SCN-infested environments.
• Standardization of methods used to screen for resistance will impact public and private soybean breeding programs and enable better definitions of "resistance" in soybean cultivar descriptions.
• Development and validation of a life history model for SCN will enable us to account for some of the variability we see in results from field experiments with SCN; this will impact SCN managment recommendations.
• Knowledge of the conditions that favor the introduction of SCN into a given habitat and its subsequent development as an economic pest will help prepare us for the spread of other invasive nematode species.

Milestones

(2007): Objective 1: Identification of objective coordinators for each sub-objective, design of web site as one outlet for annual reports generated in sub-objectives A and B, and field experiment setup for sub-objectives C, D, and E. Objective coordinators will seek funding from extramural sources. Objective 2: Collection of soil samples for determination of SCN presence/population density; greenhouse screening of soils without detectable presence of SCN for habitat suitability. Objective 3: Design database and web site for access, and collect relevant databases currently available in different locations. Establish field experiments for development of SCN life history model.

(2008): Objective 1: Complete first annual publication of reports for sub-objectives A and B. Conduct second year of experiments for sub-objectives C, D, and E. Objective 2: Continued collection of soil samples for determination of SCN presence/population density; continued greenhouse screening of soils without detectable presence of SCN for habitat suitability. Objective 3: Conduct workshop on assessment of resistance to SCN. Complete development of web site and publish standard operating procedures for screening. Continue field experiments for development of SCN life history model.

(2009): Objective 1: Second annual publication of reports for sub-objectives A and B. Complete greenhouse and growth chamber experiments for sub-objectives C, D, and E, and conduct third year of field experiments for these sub-objectives. Objective 2: Selection of sites for further sample collection for analysis of soil characteristics (soil quality assessment) followed by multivariate analysis to classify soils according to their susceptibility to SCN invasion. Objective 3: Continue field experiments for development of SCN life history model.

(2010): Objective 1: Generate extension publications based on results from 3 years of experiments for each sub-objective. Third annual publication of reports for sub-objectives A and B. Conduct fourth year of field experiments for sub-objectives C, D, and E. Objective 2: Collection of independent data set (including soil analyses and habitat suitability determination) for validation of the conceptual model developed in year 3. Objective 3: Generate checklist of key biotic and abiotic factors associated with, and predictive of, increased/decreased risk of SCN establishment, survival, and spread. Continue field experiments for development of SCN life history model.

(2011): Objective 1: Generate refereed journal publications based on results from 4 years of of experiments for each sub-objective. Fourth annual publication of reports for sub-objectives A and B. Complete assessment for each sub-objective and develop proposals for continuing research. Objective 2: Summary and dissemination of information, including journal publications and incorporation of results and recommendations into the web site database. Objective 3: Analyze data from life history experiments and publish the field model generated as a result.

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. We will tailor our outreach to the most appropriate audience. For example, the soybean variety database 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. 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. Information generated through the fundamental research (objective 2, for example) will be disseminated through refereed 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.

Literature Cited

Colgrove, A.LK., G.S. Smith, J.A. Wrather, R.D. Heinz, and T.L. Niblack. 2002. Lack of predicatable race shift in Heterodera glycines-induced field plots. Plant Disease. 86:1101-1108.

Diers, B.W., Skorupska, H.T., Rao-Arelli, A.P., and Cianzio, S.R. 1998. Genetic relationships among soybean plant introductions with resistance to soybean cyst nematodes. Crop Science 37:1966-1972.

Donald, P.A., T.L. Niblack, and J.A. Wrather. 1993. First report of Fusarium solani (blue isolate), a causal agent of sudden death syndrome of soybean in cyst nematode eggs. Plant Disease 77:647.

Donald, P. A., Pierson, P. E., St. Martin, S. K., Sellers, P. R., Noel, G. R., MacGuidwin, A. E., Faghihi, J., Ferris, V. R., Grau, C. R., Jardine, D. J., Melakeberhan, H., Niblack, T. L., Stienstra, W. C., Tylka, G. L., Wheeler, T. A., and Wysong, D. S. Soybean cyst nematode-resistant and susceptible cultivar yield in infested soil in North Central USA. (in press).

Gao, X., T. A. Jackson, K. N. Lambert, S. Li, G. L. Hartman, and T. L. Niblack. 2004. Detection and quantification of Fusarium solani f. sp. glycines in soybean roots with real-time quantitative polymerase chain reaction. Plant Disease 88:1372-1380.

Jackson, T. J., Smith, G. S., and Niblack, T. L. 2006. Heterodera glycines infectivity and egg viability following nonhosts crops and during overwintering. Journal of Nematology (in press).

Koenning, S.R. and Barker, K.L. 1995. Soybean photosynthesis and yield as influenced by Heterodera glycines, soil type and irrigation. Journal of Nematology 27, 51-62.

Lauritis, J. A., Rebois, R. V., and Graney, L. S. 1983. Development of Heterodera glycines Ichinohe on soybean, Glycine max (L.) Merr., under gnotobiotic conditions. J. Nematol. 15:272-280.

Niblack, T.L., P. R. Arelli, G. R. Noel, C. H. Opperman, J. H. Orf, D. P. Schmitt, J. G. Shannon, and G. L. Tylka. 2002. A revised classification scheme for genetically diverse populations of Heterodera glycines. Journal of Nematology 34:279-288.

Niblack, T. L. 2005. Soybean cyst nematode management reconsidered. Plant Disease 89: 1020-1026.

Niblack, T. L., and Chen, S. Y. 2004. Cropping systems. Pp. 181-206 in Schmitt, D. P., Wrather, J. A., and Riggs, R. D., eds. Biology and Management of the Soybean Cyst Nematode, Second Edition. Marceline, MO: Schmitt & Assoc.

Niblack, T. L., Bond, J., and Noel, G. R. 2004. Pages 10-61 in: Anonymous. Varietal Information Program for Soybeans. Illinois Soybean Association, Illinois Soybean Checkoff Board. 63 pp. 2005 data available online at http://www.vipsoybeans.org
Niblack, T.L. and Riggs, R.D. 2004. Variation in virulence phenotypes. Pp. 57-72. Schmitt, R.D., J.A. Wrather, and R.D. Riggs, editors. Biology and Management of Soybean Cyst Nematode, Second Edition. Schmitt & Associates of Marceline, Marceline, Missouri..

Riggs, R. D. 2004. History and distribution. Pp. 9-40 in Schmitt, D. P., Wrather, J. A., and Riggs, R. D., eds. Biology and Management of the Soybean Cyst Nematode, Second Edition. Marceline, MO: Schmitt & Assoc.

Riggs, R.D.and D. P. Schmitt. 1988. Complete characterization of the race scheme for Heterodera glycines. Journal of Nematology 20:392-395.

Smith, G.S., T.L. Niblack, and H.C. Minor. 1991. Response of soybean cultivars to aldicarb in Heterodera glycines-infested soils in Missouri. Annals of Applied Nematology 23:693-698.

Shea, K, and P. Chesson. 2002. Community ecology theory as a framework for biological invasions. Trends in Ecology and Evolution 17:170-176.

Shier, M. 2005. Soybean varieties with soybean cyst nematode resistance. University of Illinois Extension publication. 55 pp. Available online at http://www.ag.uiuc.edu/~wardt/cover.htm

Sikora, E., and Noel, G. R. 1991. Distribution of Heterodera glycines races in Illinois. Supplement to Journal of Nematology 23:624-628.

Tylka, G.L. 2004. Soybean cyst nematode-resistant soybean varieties for Iowa. Iowa State University Extension publication Pm 1649. 20 pp. Available online at http://www.isuscnvarietytrials.info/

Wardle, D.A., R.D. Bardgett, J.N. Klironomos, H. Setala, W.H. van der Putten, and D.H. Wall. 2004. Ecological linkages between aboveground and belowground biota. Science. 304: 1629-1633.

Wrather, J.A., S.R. Koenning, and T.R. Anderson. 2003. Effect of diseases on soybean yields in the United States and Ontario (1999 to 2002). Plant Health Progress doi: 10.1094/PHP-2003-0325-01-RV. [Online]. Available online at http://www.plantmanagementnetwork.org/sub/php/review/2003/soybean/

Attachments

Land Grant Participating States/Institutions

AR, IA, IL, IN, KS, MI, MN, NE, SD, VT, WI

Non Land Grant Participating States/Institutions

Tennessee