Sabry Elias, Oregon State University
Adrial Garay, Oregon State University
Emily Gatch, Washington State University
This is an Organic Seed Resource Guide article.
The importance of using high quality seeds in organic agricultural systems
Every grower has at some point observed the effects of poor seed quality: slow germination, damping-off, poor stands, weak seedlings, and mixed or genetically contaminated lots. Because organic growers depend heavily on preventative/cultural approaches to promote crop health, vigorous seed can be viewed as the first line of defense against the challenges of cold soil, soilborne pathogens, and other unfavorable conditions. Selecting appropriate varieties adapted to the area of production with disease and insect resistance, along with other desirable characteristics, is also fundamental to satisfactory crop performance and yield. In the past, many organic growers have been reluctant to use organic seed due to issues of availability, pricing, and lower quality. However, as the demand for organic seed has grown, and the industry has matured, the capacity to produce high quality seed has increased. Seed quality is assessed using the methods described below. For other seed quality tests or more information on the following tests, contact your seed laboratory.
Seed quality assessments
Genetic purity means trueness-to-type of the seed lot. It is important to assure the genetic identity which makes cultivars distinct. Genetic purity is best evaluated through a field trial in which the percentage of off-types in a seed lot is determined. Seed companies typically conduct variety trials each season to evaluate the genetic quality of contract lots; ideally, the seed lot is evaluated in comparison to the parent stock seed lot and competitors’ lots of the same variety. The results of these variety trials are made available to the grower; this information is used as a tool to guide on-farm selection of the plants in the seed crop so the seed produced from that crop is true-to-type.
Genetic purity evaluation can also include screening for transgene (GMO) contamination. Corn and beets, for example, are increasingly tested for the presence of transgenes. Seed companies typically request and pay for the testing, which is conducted at independent labs. The current National Organic Program (NOP) regulations do not specifically require testing of organic seed for GMO contamination but an increasing number of certifiers are requesting testing. Avoidance is the best approach. Seed farmers should avoid planting seed crops in regions where cross contamination is likely, observe isolation distances for cross-pollinating crops, and when available, participate in regional pinning networks.
Physical purity evaluation consists of a purity exam and a noxious weed exam. The purity exam determines the percentages by weight of pure seed, other crop seed, weed seed, and inert matter in a sample. The contracting seed company typically defines the purity standard for a particular seed crop and communicates this standard to the grower. The noxious weed exam determines the rate of occurrence and identity of noxious weeds as specified by the Federal Seed Law. This is called the “All States Noxious Weed Exam.” In addition, there is a noxious weed list specified by each state seed law; these weed seeds are prohibited if seeds are to be marketed as "certified seed". These tests are performed by a registered seed technician at a certified lab (see the list of some seed testing laboratories below). Using seed free from weed or other crop seeds, along with planting seed in a clean seedbed, reduces the cost of weed control program.
Other Seed Quality Attributes
Seed viability, vigor, and the presence/absence of seedborne pathogens or other microorganisms are among the attributes needed to make a reasonable prediction of seed performance in the field.
- Viability testing: Viability testing determines the percentage of live seeds in a sample that have the potential to produce normal seedlings under favorable germination conditions. The USDA mandates that all seed sold commercially be tested by a certified lab within six months of sale and must meet minimum germination standards that are set for each major crop group. Individual states have their own seed laws governing viability, so seed companies typically set their own internal minimum germination standards to meet or exceed the strictest of the state laws. One problem with germination testing is that it is ineffective when seeds are dormant (as they won't germinate even when viable). The tetrazolium (TZ) test is a quick biochemical test that evaluates seed viability based on seed respiration. This test is useful as it measures the percent live seeds in a sample regardless of the seeds’ dormancy status. The test can be performed in 24 to 48 hours.
- Vigor testing: Vigor testing moves beyond a simple assessment of germination by evaluating how quickly seed germinates and whether the germinating seeds and developing seedlings are “normal” and robust in the early stages of growth. Vigor tests measure the potential for rapid, uniform emergence of seeds under a wide range of field conditions. Examples of vigor tests are the cold test, the accelerated aging test, and the conductivity test. The cold test and accelerated aging tests subject seeds to stress conditions to assess their vigor, while the conductivity test measures the level of exudates secreted by the seeds, or the “leakiness,” which correlates to low vigor.
- Seedborne diseases and saprophytic (non-pathogenic) fungi: Seedborne disease testing indicates whether your seed carries diseases that will have a significant impact on the health and productivity of the crop. For more information, see Disease Management in Organic Seed Crops. In addition to seedborne pathogens, many other non-pathogenic fungi and bacteria can grow on seed surfaces, and high populations can reduce seed viability and vigor. Proper harvest, processing, and storage methods are key to avoiding storage mold in seed lots.
One of the ways in which seed quality is regulated is through adherence to a system of seed certification that is overseen by state seed certification agencies. This system has not typically been used by many smaller, independent specialty seed companies as these companies often have their own internal quality control systems. However, seed certification is an important mechanism for ensuring seed quality and should be understood by growers, buyers, and users of seed.
Seed classes indicate how many generations a given seed lot is removed from the plant breeder or institution that was the source of the variety; these classes provide the distributer or buyer information about the history and quality of a seed lot.
- Breeder seed is seed produced by the originating plant breeder or institution/private company.
- Foundation seed is seed produced from breeder seed and is controlled by license from that source.
- Registered seed is produced from foundation seed and is the typical parent seed of certified seed.
- Certified seed is produced from either breeder seed or foundation seed, and is at most two generations from foundation seed.
Certified seed crops must pass both field inspection and laboratory analysis. The field must be planted from the proper class of seed, have appropriate isolation, and be free of problem weeds and diseases. After harvest, a sample of the seed crop must be sent to an official seed certification laboratory for germination and purity analyses. The seed must meet the standards set by the seed certifying agency.
Seed that has passed the field inspection and the laboratory analysis can be tagged as Certified seed. In addition to the Certified tag there must also be an analysis tag with information on kind (e.g. corn), variety, and purity (percent pure seed, other seed, inert matter, weed seeds, germination).
State Testing and Certification Resources
- Oregon State University Seed Laboratory.
Link: http://seedlab.oregonstate.edu/ (verified 15 Jan 2023).
The OSU Seed Laboratory provides seed testing services, seed quality-related research, and educational support, e.g., seed classes, workshops, and educational materials. Testing services are provided for a broad range of species, including grasses, trees, shrubs, cereals, legumes, vegetables, flowers, and native species. Seed samples can be for official, Oregon-certified, commercial, research, breeding, conservation, and other programs. Tests include purity, viability, vigor, and other special seed quality traits. Purity tests include determination of pure seed percentage in a sample, noxious weed exam, crops and weeds, undesirable grass seeds, sod quality, and pests and diseases. Viability tests include standard germination tests and viability by TZ. Special tests include ploidy by cytometry, greenhouse grow-out, vigor, endophyte, seed moisture content, X-ray, and others. Tests can be conducted following the AOSA or ISTA rules, depending on customer needs and seed destination.
Oregon State University
Corvallis, OR 97331
- Oregon State University Seed Certification Program.
Link: https://seedcert.oregonstate.edu/ (verified 15 Jan 2023).
The OSU seed certification program reviews and retains crop production records, performs field and laboratory evaluations, helps maintain and increase seed and propagation material quality, and helps ensure varietal purity. It also maintains records on field history, planting stock, and eligibility of new plantings to be submitted for certification. It conducts record review and physical inspection of each submitted field, tracking all movement of seed from initial planting through harvest, cleaning, and packaging, to ensure relative freedom from contamination and to assure the end user that materials purchased are as described on the label. It also certifies grasses, legumes, grains, mint, potatoes, and other crops (e.g., kale, radish, sugar beets, and turnip). Application forms and requests for certification are available from the office of the OSU Extension Service in the county where the crop is grown.
Department of Crop and Soil Science
Oregon State University
351 Crop Science Bldg.
Corvallis, OR 97331
- Oregon Department of Agriculture Commodity Inspection Division.
Link: https://www.oregon.gov/ODA/programs/PlantHealth/Pages/SeedTesting.aspx (verified 15 Jan 2023).
The Commodity Inspection Division offers official verification of seed processes to facilitate the movement of commodities in domestic and international markets. Official letters of verification are provided to fulfill export, contract, or customer requirements for an independent third party or official government review of seed processes.
Verification services include:
- Seed treatment verification
- Seed blend/mix verification
- Verification of the fumigation of seed shipments
- Seed package weight verification
- Shipment count/quantity verification
- Oregon Department of Agriculture Plant Division Plant Health Section.
Link: http://oregon.gov/ODA/CID/PLANT_HEALTH/index.shtml (verified 15 Jan 2023).
The Plant Health Section conducts laboratory tests to detect specific seed-borne fungi, bacteria, nematodes, pests, diseases and other miscellaneous problems on seeds of grasses, clover and other crops. These tests are performed at the request of Oregon seed producers to meet the phytosanitary requirements of their international customers.
Dr. Nancy Osterbauer
635 Capitol St NE
Salem, OR 97301
- Oregon Department of Agriculture Seed Certification.
Link: https://www.oregon.gov/ODA/programs/MarketAccess/SeedRegProgram/Pages/Se... (verified 15 Jan 2023).
The Oregon Department of Agriculture offers a variety of testing services for farmers and growers that export their crops or products to other countries. These tests are designed to meet the phytosanitary, or quarantine, requirements of the international customer.
The services offered include:
- Seed testing for pathogens
- Seed field inspection and certification
- WSDA Seed Testing Laboratories and Inspection Services.
Link: https://agr.wa.gov/services/inspections-and-investigations/inspections/s... (verified 15 Jan 2023).
Victor Shaul, operations manager
21 N. 1st Ave.
- WSDA Commodity Inspection Division, Seed Program
Lee Graham, seed inspector
821 E. Broadway, Suite 4
Moses Lake, WA 98837
- WSDA Plant Pathology Laboratory
Provides phytosanitary analysis and certification for shipping.
- Nematodes and viruses
24106 N. Bunn Rd.
Prosser, WA 99350-8694
- Bacterial and fungal pathogens
3939 Cleveland Ave. SE
Olympia, WA 98501
- Nematodes and viruses
- The Seed Testing Lab of the State of Idaho Department of Agriculture.
Link: https://agri.idaho.gov/main/laboratories/seed-lab/ (verified 15 Jan 2023).
Offers germination, tetrazolium, purity, noxious weed, cold-test, and other seed quality tests for over 200 crops.
2240 Kellogg Lane
Boise, ID 83712
- California Department of Food and Agriculture
The Seed Laboratory
3294 Meadowview Road
Sacramento, CA 95832-1448
- California Seed & Plant Lab, Inc.
Link: http://www.calspl.com/ (verified 15 Jan 2023).
7877 Pleasant Grove Rd
Elverta, CA 95626
- STA Laboratories.
Link: http://www.stalabs.com/ (verified 15 Jan 2023).
5653 Monterey Frontage Road
Gilroy, CA 95020
California Customer Service: 888-782-5220
Transgene (GMO) Testing
- OMIC USA
A private GMO testing company offering third-party non-GMO certification
3344 NW Industrial St.
Portland, Oregon 97210
- Genetic ID.
Link: http://www.genetic-id.com/ (verified 15 Jan 2023).
A private GMO testing company offering third-party non-GMO certification.
P.O. Box 1810
Fairfield, Iowa 52556
Sample Delivery/Laboratory Address:
501 Dimick Drive
Fairfield, Iowa 52556
Phone: 641-472-9979, 877-366-0790 (Toll Free USA/Canada)