Progress 07/07/97 to 06/30/05

Outputs
In response to the major increase in worldwide seed health regulations in the 1990s, the Seed Science Center at Iowa State University (ISU), in collaboration with the American Seed Trade Association and USDA-APHIS developed the National Seed Health System (NSHS) that was authorized under 7 CFR Parts 300 and 353 in the Federal Registrar on 7/18/01. The seed pathology program at ISU provided the scientific components of the system that accredits organization that test seeds for plant pathogens to meet international phytosanitary regulations. This process required the development and implementation of a peer review system to standardize over 70 seed health methods. Protocols for disease inspection in seed production fields, sampling of seeds for laboratory seed health testing, and visual inspection of seeds for plant pathogens were also established. The website, www.seedhealth.org, describes the system and provides necessary documentation for members and applicants. To date 11 organizations have been accredited under an audit system designed for this program. As a result, most of the field crop and vegetable seeds exported from the USA receive phytosanitary certificates based on NSHS standards. There is now strong evidence that other countries are adopting NSHS methods as standards for seed health testing. The US seed industry has encountered substantial economic and logistical problems due to the implementation by trading partners of phytosanitary regulations that are scientifically unjustified. To address these concerns, the seed pathology program at ISU collaborated with CAB International in the UK to develop a database on seedborne diseases that provides a powerful information tool to challenge unjustified regulations. This database, first published in 1997, is in CD and Web formats and has been updated every year since 2003. Seed Science Center personnel have used this as the primary scientific information source in workshops in Central and South America, Africa, and Asia evaluated the merits of phytosanitary regulations in these regions. These activities not only resulted in the elimination of large numbers of unjustified regulations, but also identified seed-borne pathogens that are of high risk to crops throughout the world. Seed discoloration of soybeans, caused by bean pod mottle virus (BPMV) is a economically important disease, particularly for food grade soybean producers. Studies on this problem showed that the over wintering and 1st generation of bean leaf beetles were the more important sources of the virus than that transmitted by infected soybean seeds. Insecticide treatments that targeted the 1st generation alone or in combination with the over wintering generation of the bean leaf beetle showed significantly fewer BPMV-discolored seeds at harvest time. Seed conditioning equipment was able to removing Sclerotinia sclerotiorum-infested seeds from soybean seed lots, based on seed size. Artificially inoculated soybean seeds transmitted the pathogen to seedlings in field soil under greenhouse conditions. Seed treatments showed promise as a means of eradicating seedborne infection.

Impacts
The National Seed Health System is now being used as model for accreditation and method standardization at national and international levels. A plan was submitted to the USDA agencies CSREES and APHIS for an accreditation system for the National Plant Disease Network that contains many elements of the NSHS. A proposal also was made to the International Seed Federation to use the NSHS peer review system to expedited standardization of internationally-accepted seed health methods. Annually over $800 million worth of seeds are exported from the U.S. The science based phytosanitary regulations are key to maintaining such exports. The information generated from research on BPMV and discolored seeds are instrumental in maintaining competitiveness of the U.S. seed companies.

Publications

• No publications reported this period

Progress 01/01/04 to 12/31/04

Outputs
Three organizations were accredited in the National Seed Health System NSHS in 2004 to carry out seed health tests or field inspection for the purpose of receiving Federal Phytosanitary certification. These additions bring the total accredited organizations to ten. Changes instigated in the peer review system to standardized seed health methods in the NSHS have expedited the process without compromising quality. A plan entitled, A Strategic Approach to Resolution of Scientifically Unjustified Phytosanitary Regulations That Adversely Affect U.S. Produced Seeds in Export Markets, was developed for the NSHS in 2004. This is designed to complement other programs at ISU, such as the current phytosanitary harmonization project in South-East Asia. Work began in 2004 on a joint project with Iowa State University, the University of Georgia and Clemson University to develop technology to assay numerous pathogens in DNA extracted from seeds. Responsibilities have been assigned to these partners, with methodology of DNA extraction from seeds being the primary activity at Iowa State University. Research on the soybean seed discoloration has indicated that control of the overwintering and 1st generations of the bean leaf beetle could be an effective means of reducing the problem. To that end a survey was carried out in sixteen commercial soybean fields in Iowa in 2004. All fields were planted with seed treated with Guacho (imidocloprid). A strip of each field was also planted with untreated seeds. Seed treatment significantly reduced feeding of the overwintered population of the bean leaf beetle in the treated compared to the untreated part of each field. Weather conditions in the state, however, were not conducive to the development of a significant population of the 1st generation of the insect. A negligible amount of the activities of seed discoloration was recorded in the seeds at harvest time.

Impacts
The National Seed Health System is now being used as model for accreditation and method standardization at national and international levels. A plan was submitted to the USDA agencies CSREES and APHIS for an accreditation system for the National Plant Disease Network that contains many elements of the NSHS. A proposal also was made to the International Seed Federation to use the NSHS peer review system to expedited standardization of internationally-accepted seed health methods.

Publications

• Pataky, JK, Block,CC; Michener, PM, Shepherd, LM, McGee, DC. 2004. Ability of an ELISA-Based Seed Health Test to Detect Erwinia stewartii in Maize Seed Treated with Fungicides and Insecticides. Plant Dis. 88:633-640.

Progress 01/01/03 to 12/31/03

Outputs
Fifteen new seed health methods were standardized for the National Seed Health System (NSHS) in 2003 and published at the NSHS website www.seedhealth.org. Research on seed health methods resulted in two PCR-based tests for detection of Clavibacter michiganensis subp. michiganesis in tomato seed and Erwinia stewartii in corn seeds. The first of a series of phytosanitary resolution workshops was held in Thailand in 2003, with the purpose of harmonizing phytosanitary regulations that affect trading and exchange of seeds produced in South-East Asia. Research on the soybean seed discoloration has indicated that control of the overwintering and 1st generations of the bean leaf beetle could be an effective means of reducing the problem. To that end a survey was carried out in 30 commercial soybean fields in Iowa in 2003. All fields were planted with seed treated with Guacho (imidocloprid). A strip of each field was also planted with untreated seeds. Seed treatment significantly reduced feeding of the overwinterd population of the bean leaf beetle in the treated compared to the untreated part of each field. Weather conditions in the state, however, were not conducive to the development of a significant population of the 1st generation of the insect. Very little seed discoloration was recorded in the seeds at harvest time. Although the lack of discolored seeds did not allow the impact of seed treatment on seed discoloration to be evidenced, it did confirm the importance of the 1st generation of the insect as a source of the BPMV.

Impacts
Over 80 seed health methods for vegetable and field crops that meet standards of the US National Seed Health System are now available at the NSHS web site. This not only improves the quality assurance programs of US seed companies, but enhances the reputation of the US government in meeting international seed health standards. By testing the research findings on management of soybean, seed discoloration are now being tested under grower conditions in Iowa, the practical value of the strategy should become evident.

Publications

• McGee, D. C. 2003 The US National Seed Health System: a diagnostic network model Pp. 20-21 Developing a World Class Plant Pathology Diagnostic Network (for Australia) Workshop Proceedings, Christchurch , New Zealand, February 8, 2003.
• Murillo-Williams, A., McGee, D.C., Wilke, A., and Munkvold, G. 2003. Temperature effects on systemic infection of maize by Fusarium verticillioides. Phytopathology 93:S64
• McGee, D.C. and Shepherd, L. 2003.The USA National Seed Health System. 8th International Conference of Plant Pathology, Christchurch, New Zealand, February, 2003. P. 323.

Progress 01/01/02 to 12/31/02

Outputs
Key elements were put in place to allow the US National Seed Health System (NSHS) to begin operation. These included an audit system that defined auditor qualifications, a training system for auditors, and checklists for auditor use. Standardized seed health methods and field inspection procedures were published on the NSHS website <www.seedhelsth.org>. Six organizations were accredited by the NSHS in 2002. Under the Phytosanitary Resolution component of the NSHS, qualitative Pest Risk Analyses were prepared for 21 seedborne pathogens in nine vegetable crops to meet a requirement of the Brazilian Government related proposed import regulations on vegetable seeds. The administration unit for the NSHS, the Seed Science Center continues to coordinate a peer review system to establish standardized seed health tests for the NSHS. 2. Studies of the seed discoloration problem in soybeans showed that the 1st generation of bean leaf beetles, and to a lesser extent, the over wintering generation, were the main source of discoloration caused by BPMV of harvested soybeans. The 2nd generation was a not significant source of the virus. Insecticide treatments that targeted the 1st generation alone or in combination with the over wintering generation for bean leaf beetle showed significantly fewer BPMV-discolored or shriveled seeds and more normal seed at harvest time.

Impacts
Six organizations are now accredited in the US National Seed Health System to can carry out the necessary seed heath testing and /or field inspection of growing seed crops to obtain Federal Phytosanitary Certificates for seed lots exported from the USA. The US seed industry met the requirement to provide Pest Risk Analyses on seedborne pathogens to the Brazilian Government. This was necessary to maintain the export market for vegetable seeds in that country. Soybean growers can begin testing insecticide strategy that targets the overwintering and 1st generations of the bean leaf beetle in the productions fields in Iowa.

Publications

• McGee DC. 2002. Pest Risk Analysis (PRA) of economically important, seed transmitted plant pathogens of vegetables for PRA requirements of the government of Brazil for imported seeds. Phytosanitary Resolution Program, National Seed Health System 296 pp.
• McGee DC. 2002. The National Seed Health System. 38th Illinois Corn School, pp 72-76.

Progress 01/01/01 to 12/31/01

Outputs
a) The second up-date of the Electronic Crop Protection Compendium (CPC) was issued by CAB International in 2001. The Database on Seedborne Diseases component of the CPC continues to be edited at the Seed Science Center, Iowa State University. b) The National Seed Health System was published by USDA-APHIS in the Federal Register and became on July 18, 2001 and was activated one month later. As the administration unit for the NSHS the Seed Science Center continues to coordinate a peer review system to establish standardized seed health tests for the NSHS. It also is the primary source of key documents for the system, including application materials, auditing practices, and training of personnel in accredited entities. c) Research on the soybean seed discoloration that has become of increasing concern in recent years has shown the following: 1. The bean leaf beetle infestation and incidence of seed infection by bean pod mottle virus (BPMV) cause seed discoloration and significant reduction in crop yield. 2. Seed treatment with systemic insecticide and one foliar spray with insecticide have the capacity to reduce the impact of the first and second generations of the bean leaf beetle. These remain the most economic control practice for this problem.

Impacts
The database on seed borne diseases and the development of the National Seed Health System will facilitate trading and exchange of US seeds throughout the world. Results of the study on soybean seed discoloration have pin-pointed a strategy to manage the disease. This will be tested in 2001.

Publications

• McGee DC. 2001 - Webmaster National Seed Health System Web Site
• Daniels JL, GP Munkvold and DC McGee. 2001. Comparison of infected seed and bean leaf beetles as inoculum sources for bean pod mottle virus. Phytopathology 91, 6 S20.
• McGee DC. 2001 A risk analysis model using the CABI database. Phytopathology 91, 6 S2153

Progress 01/01/00 to 12/31/00

Outputs
a) The first up-date of the Electronic Crop Protection Compendium (CPC) was issued by CAB International in 2000. The Database on Seedborne Diseases component of the CPC continues to be edited at the Seed Science Center, Iowa State University. b) The final rule for the National Seed Health System was published by USDA-APHIS in 2000 and the system is expected to start in early in 2001. The Seed Science Center, as the administration unit for the NSHS, is coordinating a peer review system to establish standardized seed health tests for the NSHS. These methods will be published in the NSHS Reference Manual on Seed Health Tests. c) Research on the soybean seed discoloration that has become of increasing concern in recent years has shown the following: 1. A strong correlation exists between the incidence of seed infection by bean pod mottle virus (BPMV) and discolored soybean seeds. 2. Discolored soybean seeds are reduced in size and weight, but warm germination and accelerated aging test values were not reduced. 3. The bean leaf beetle insect vector is a major source of inoculum for BPMV, while seedborne inoculum is of minor source. 4. Imidacloprid (Gaucho) seed treatment gave some early season protection against the bean leaf beetle, which was reflected in reduced plant infection by BPMV and seed discoloration at harvest at one experimental site. However, no control of seed discoloration was evident at a second site, where higher insect populations occurred.

Impacts
The database on seed borne diseases and the development of the National Seed Health System will facilitate trading and exchange of US seeds throughout the world. Results of the study on soybean seed discoloration have pin-pointed a strategy to manage the disease. This will be tested in 2001.

Publications

• McGee DC, Munkvold G and Daniels J. 2000. The relative importance of infected soybean seeds and bean leaf beetles as inoculum sources for bean pod mottle virus. Pages 103-112 in: 12th Annual Integrated Crop management Conference, Ames, IA
• McGee DC. 2000. Management of seed-borne fungal diseases. Pages 144-147 in: Proc. ISTA/Govt, of Japan Workshop on Seed Pathology, Nagoya, Japan, 1998.
• McGee DC. 2000. Pathology of seed deterioration. Pages 53-63 in: Genetic Impovement of Seed Quality. Special Publication. No. 31, Crop Science Society of America.
• McGee DC. 2000. Editor Database on Seedborne Diseases component of the CAB International Crop Protection Compendium. CABI, Wallingford, UK.

Progress 01/01/99 to 12/31/99

Outputs
1. The final issue of the Electronic Crop Protection Compendium was issued as a CD-ROM by CAB International in 1999. This contained Database on Seedborne Diseases (DSD) for approximately 300 economically important seed-borne pathogens. These datasheets were either written or edited at the Seed Science Center, Iowa State University. Information is provided on the economic importance, geographic distribution, and seedborne aspect of each pathogen in the DSD. The database will be updated on an annual basis until 2003. 2. Infection of seeds by Sclerotinia sclerotiorum was shown to be correlated with location of infection on the soybean plant stems under conditions of natural infection in the field. A technique was used to demonstrate transmission of the pathogen from artificially inoculate soybean seeds to seedlings in field soil under greenhouse conditions. Seed treatments showed effectively reduced seed transmission, of the pathogen. 3. Seed discoloration of soybeans has become an increasingly important problem, particularly for food grade soybean producers. Preliminary results in 1998 had suggested that Phomopsis seed decay was associated with the discoloration. Further studies have identified bean pod mottle virus as the primary cause. Work is underway to determine the relative importance of infected seed and the bean leaf beetle as sources of inoculum for bean pod mottle virus. 4. A peer review system to establish reference seed health tests for the proposed National Seed Health System is being coordinated by the Seed Science Center. Five methods have been evaluated and will be published in the NSHS Reference manual on methods. 5. Several new seed health test methods were introduced in the seed health testing program in the Seed Science Center to meet new phytosanitary regulations of countries importing US seeds.

Impacts
The new seed health tests will enable the US seed industry to export seeds valued at millions of dollars by meeting new phytosanitary regulations of importing countries. The Electronic Crop Protection Compendium provides a reference source of information for 300 seed-borne pathogens including the economic importance, geographic distribution, and seedborne aspect of each pathogen.

Publications

• Block, C.C., Hill, J.H., and McGee, D.C. 1999. Relationship between Late-Season Foliar Disease Severity of Stewart's Bacterial Wilt and Seed Infection in Maize. Plant Dis. 83:527-530.
• Arias Rivas, B., McGee, D. and Burris, J.S. 1998. Treatment of maize seeds with polymers for control of Pythium spp. Fitoplatologia Venezolana 11(1):10-15.
• Arias Rivas, B,. McGee, D. and Burris, J.S. 1998. Potential of polymers as binding agents for fungicie in control of Pythium spp. in maize. Agronomia Tropical 48:471-488.
• McGee, D.C. 1999., Database on Seedborne Diseases D. McGee Editor, Crop Protection Compendium CD-ROM, Global Module 1, CAB International, Wallingford, UK.
• McGee, D.C. 1999. The National Seed Health System. In: Proc. Annu. Soybean Res. Conf. 53. American Seed Trade Association, Washington DC. (in press).
• McGee, D.C. 1999. Pathology of seed deterioration. Pages 53-63. In: Genetic Improvement of Seed Quality. Special Publication. Crop Science Society of America. (in press).

Progress 01/01/98 to 12/31/98

Outputs
IMPACTS OF RESEARCH. (1) The second issue of the Electronic Crop Protection Compendium was issued as a CD-Rom by CAB International in 1998. This contained datasheets on 170 seed-borne diseases that were either written or edited at the Seed Science Center, Iowa State University as part of a scientifically based database that will eventually comprise 400 datasheets. Information is provided on the economic importance, geographic distribution, incidence, transmission, treatment and testing of seed-borne diseases. (2) Seed conditioning equipment was shown to be capable of removing Sclerotinia sclerotiorum -infested seeds from commercial-scale soybean seed lots, based on seed size. Infection of seeds in seed production field was correlated with location of infection on the plant stems. A technique to artificially inoculate soybean seeds was used to demonstrate transmission of the pathogen from infected seeds to seedlings in field soil under greenhouse conditions. Seed treatments showed promise as a means of eradicating seedborne infection. (3) Seed discoloration of soybeans has become an increasingly important problem, particularly for food grade soybeans producers. Preliminary results suggest that soybean mosaic virus and Phomopsis seed decay are the primary causes of discoloration. Further studies should be directed at minimizing the development of the problem in production fields and eliminating discolored seeds during seed conditioning. (4) As part of national and international efforts to improve seed health systems, the Seed Science Center played a prominent role in establishing procedures for standardization and publication of seed health test methods. A phytosanitary resolution system was also devised to facilitate the incorporation of scientific data into challenges to phytosanitary regulations that adversely impact for use US seed producers. (5) Several new methods were introduced in the seed health testing program in the Seed Science Center to meet new phytosanitary regulations of countries importing US seeds.

Impacts
(N/A)

Publications

• McGee, D. C. 1998. Initiatives to improve the international seed health system. Seed Technology. Seed Technology 20: 18-22.
• Block, C. C., Hill, J. H., and McGee, D. C. 1998. Seed transmission of Erwinia stewartii in field and sweet corn. Plant Dis. 82: 775-780.
• Walcott, R. R., McGee, D. C., Misra, M. K., 1998. Detection of asymptomatic fungal infections of soybean seeds using ultrasound analysis. Plant Dis. 82:584-589.

Progress 01/01/97 to 12/31/97

Outputs
(1) The first issue of an Electronic Crop Protection Compendium was issued as a CD-Rom by CAB International in 1997. This comprised datasheets on 70 seed-borne diseases written at the Seed Science Center, Iowa State University as part of a scientifically based database that will eventually comprise of 500 datasheets. Information is provided on the economic importance, geographic distribution, incidence, transmission, treatment and testing of seed-borne diseases. (2) . Progress was made on development of a sensitive and practical seed health assay for Clavibacter michiganensis subsp. nebraskensis (Cmn), the causal agent of Goss's wilt of corn. Tests with seed extracts from two corn seed lots, known to be contaminated with Cmn, showed a 5-10 times increase in recovery rate of Cmn on sCNS compared to that on the original CNS selective medium for this pathogen. Isolates were confirmed as Cmn by biochemical and pathogenicity testing. (3) Work continued on finding and standardizing seed health tests needed to meet the demand for new tests as phytosanitary regulations become more prevalent throughout the world. (5) A soybean seed-lot with extensive internal seed infection with Sclerotinia sclerotiorum was identified for study of the distribution of the pathogen in relation to seed size. Results showed infected seeds were confined to the size category that can pass through a 12/64 in. slotted screen size. Seeds in the infected categories also contain substantial numbers of seeds that were misshapen, shriveled or green.

Impacts
(N/A)

Publications

• McGee, D. C. 1997. Developments in Seed Health Testing Policy. Pages 115-118 in Seed health testing: Progress towards the 21st Century. J. D. Hutchins & J. C, Reeves (eds.) CAB International, Wallingford,
• McGee D. C. (Ed.) 1997. Plant Pathogens and the Worldwide Movement of Seeds. APS Press St. Paul, MN 109 pp.
• Olanya, O. M., Hoyos, G. H., Tiffany, L. H., and McGee, D. C. 1997. Waste corn as a point source of inoculum for Aspergillus flavus in the corn ecosystem. Plant Dis. 81:576-581.
• Munkvold, G.P., McGee, D.C., and Carlton, W. M. 1997. Importance of different pathways for maize kernel infection by Fusarium moniliforme. Phytopathology 87:209-217.