Accurate Testing, Exceptional Service:
ISU Seed Testing Laboratory services include: Standard Germination Testing (AOSA, ISTA), Purity Testing and Noxious Weed Exams, Seed Health Testing (NSHS-Accredited), Trait/AP Testing, Vigor Testing (Cold, Saturated Cold, and AA), Tetrazolium Testing (Viability and Vigor), and Fast Green and Hypochlorite Soak Tests.
Warm Standard Germination
Duration: Typically 7-10 days.
Warm germination tests are used for labeling purposes and give a reasonable idea of field emergence under favorable conditions. A minimum of 400 seeds is required for an AOSA, NSHS, or ISTA official test. Tests can be conducted in rolled brown paper towels (8 reps of 50 seeds), on blue blotter paper, on crepe cellulose paper (Kimpak®), and Kimpak® covered with sand. Corn and soybeans are normally tested at 25°C (77°F) for 7 days. A test on any species can be ended at the required germination period if an analyst feels maximum germination has been reached. A test can be extended 2 days for slow-growing seedlings.
Duration: Typically 7-10 days.
Sand germ tests are done the same as Warm germination, except that a layer of moist sand is placed over the seeds and Kimpak®. This test is useful in suppressing some fungi. It also aids in uniform uptake of water, especially in low moisture soybean seed. For soybean samples, sand germination results are the same or slightly higher than warm germination results. In the instances of fungal problems or extremely dry seed, the sand germination can be markedly higher. We find that the higher the germination of the seed lot, the less positive effect the sand has on the results.
Cold Germination:The Iowa Cold Test
Duration: Typically 12-14 days.
The cold germination test gives a reasonable idea of emergence under less than ideal conditions. Two replications of 100 seed are placed on Kimpak® that has been moistened and chilled overnight at 10C. The seeds are covered with a non-sterile sand/soil mixture and returned to 10C for seven days without light. The cart is then moved to 25C for five to seven additional days. Seedlings that emerge through the sand/soil mixture are evaluated according to AOSA Rules. An extended cold test is also available which exposes seed to two weeks in the cold instead of one.
Saturated Cold Germination
Duration: Typically 9 or 10 days.
The saturated cold germination test is another way of determining how well a seed lot will do under unfavorable conditions. Some consider it to be a more severe test than the tray method. Seeds are placed on a thin layer of saturated soil on paper towels over a special tray. Seeds are turned so that the side of the corn kernel closest to the embryo is down against the soil. The cart is placed in 10°C for seven days without light and then moved to 25°C for two to three more days. The number of normal seedlings, abnormal seedlings, and dead seed are recorded.
Duration: Approximately 10 days
Accelerated aging is another vigor test that can be used to estimate field emergence. Its advantage is that virtually any type of seed can be tested using the AA test. The test consists of placing a species specific mass of seed (not a certain number) on an elevated screen. The screen is placed into an acrylic box that contains 40ml of water. When the box is covered with a tight-fitting lid and placed into the AA chamber, the seeds are exposed to high temperature and humidity. The aging period ranges from 48 to 96 hours depending on type of seed (corn and soybeans: 72 hours). The seeds are removed from the chamber and promptly planted on blotters, paper towels, or Kimpak®. Seeds planted on Kimpak® are covered with a layer of moist soil. The seeds are grown a period of time similar to a warm germination test and the number of normal seedlings are reported.
Tetrazolium (TZ) Test
Duration: 2 days
The tetrazolium test gives a rapid estimation of warm germination results. It can also be used for small-seeded species in determining the viability of ungerminated seed at the end of the germination period. Two reps of 100 seeds (typically) are placed between moist brown paper towels or blotter paper overnight. The next day the seeds are pierced, cut in half, or left whole (depending on species) and placed in tetrazolium solution. After a short period of time, the seeds are examined for staining patterns. The tetrazolium test can also be used to detect frost damage, estimate vigor, or diagnose seed lot problems.
Duration: Typically 6 - 7 days
Herbicide Bioassay (HB) tests can be used to determine the percentage of seeds in a lot that are tolerant to a herbicide (genetic purity) or it can be used to detect the absence of tolerance (adventitious presence). We recommend using immunoassay or PCR tests to determine whether seeds are free of biotech traits. HB tests are available for corn (Roundup Ready®, Liberty Link®, Clearfield®), soybeans (Roundup Ready®, STS®), cotton (Roundup Ready®), and canola (Roundup Ready®). Herbicides (active ingredients) used in testing are glyphosate (WeatherMax®), glufosinate (Liberty®), Imazethapyr (Lightning®), and chlorsulfuron (Glean®)
Duration: One day
The fast green test is conducted on corn and sorghum seeds. Briefly exposing seeds to fast green solution and then rinsing off excess solution results in damage to the surface of seeds becoming apparent. Damage is classified as light (damage to base of seed or small areas away from the embryo), medium (damage extending along either side of the embryo) or severe (damage to seed over the embryo). The test is especially useful in setting equipment in seed conditioning facilities so as to maximize output while minimizing damage from machinery.
Duration: Seeds - One to three hours, Leaves - 6 to 8 days
Immunoassay tests (ELISA plates and Lateral Flow Strips) utilize antibodies of what is being tested for (biotech traits) to determine if protein for that trait is present (yes/no or qualitative) or how much is present (quantitative). Genetic purity testing requires checking individual seeds or leaves. Generally, leaves contain more protein than seeds and therefore are very useful for detecting traits that don't necessarily produce much protein in seeds (i.e. Bts). ELISA plates are a natural for this (YieldGard Corn Borer®, YieldGard Rootworm®, YieldGard Plus®, or Herculex®). To test for the absence of biotech traits, combs containing strips for each trait can be used to check for all traits simultaneously. An alternative is to use a single strip that detects stacked traits. A critical factor is knowing the capabilities of the ELISA plate or lateral flow strip. Detection limits range from 1 trait seed in 70 conventional seeds to 1 trait seed in 1000 conventional seeds.
Polymerase Chain Reaction (PCR) is a high-tech method to extract, increase, detect and identify DNA from biotech traits (if present). It is highly sensitive and especially good in determining absence of biotech traits. PCR can give qualitative or quantitative results. Attention to detail and in depth knowledge of molecular biology and available biotech traits are critical to success in using PCR.
The Iowa State University Seed Testing Laboratory conducts many types of tests on more than 300 species of seed. A partial list of tests appears on this page. Contact Customer Care at 515-294-6826 for more information about the tests we offer.
Test duration depends upon the crop being tested and the type of test being performed. If you require more information than is available on this page, contact Customer Care at 515-294-6826.
"The ISO 9000 (the International Organization for Standardization) family of standards represents an international consensus on good management practices with the aim of ensuring that the organization can time and time again deliver the product or services that:
—Meet the customer's quality requirements, and
—applicable regulatory requirements, while aiming to
—enhance customer satisfaction, and
—achieve continual improvement of its performance in pursuit of these objectives."
—AOSA — (The Association of Official Seed Analysts) Rules for Testing Seeds for domestic and international seed movement.
—ISTA (The International Seed Testing Association for international movement of seed.
—Canadian M &P — Seed to be shipped into Canada.
—NSHS — The National Seed Health System – phytosanitary testing
—Biotech Trait Providers requirements — trait testing
Our ISO 9001:2008 Certification is our guarantee to our customers that rigorous standards areconsistently applied to every test we perform.
Seed Health Testing
The Iowa State University Seed Health Testing Laboratory tests for over 200 viral, bacterial, and fungal pathogens on most crops, including corn, soybeans, vegetables, and flowers using a variety of methods. Tests are available to address nearly all phytosanitary and quality assurance concerns. All phytosanitary certification is performed in accordance with National Seed Health System (NSHS) standards. The Seed Heatlth Testing Lab is NSHS accredited, in accordance with USDA-APHIS regulations.
Price Lists:The Iowa State University Seed Testing Laboratory performs hundreds of tests on nearly every species of seeds imaginable. Current price lists are available on our Online Services Webpage (secure web lockers) or copies can be requested by contacting ISU Seed Lab Customer Service at 515-294-6826 or firstname.lastname@example.org.
More In-Depth Testing InformationWhy are soybean germination tests that include hard and swollen seeds extended for up to five days?
The Association of Official Seed Analysts (AOSA) Rules for Testing Seeds allows any seed test to be extended an additional two days for reasons such as a slow growing seed lot (inbreds). The Rules also allow for swollen seeds to be placed on new planting media and testing extended for up to five days. Swollen seeds are hard seeds that at some point took up moisture during a germination test. Hard seeds have a seed coat that doesn’t allow moisture to be taken up—often the result of hot and dry growing conditions. Hard seededness is a desirable trait for species used in native planting, but is not a desirable trait for row crops where smaller plants might be crowded out. Some seed species are mechanically scarified to break hardseedness (however, this is not the case in soybeans).
What tests are required for labeling purposes?
Labeling requirements require the following tests:
—Standard (Warm) Germination
—Noxious Weed Exam
How do soybean warm germ results typically compare with sand germ results?
Typically sand germination results are the same or slightly higher than warm germination results. In instances of fungal problems or extremely dry seed, the sand germination can be higher. We find that the higher the germination of the seed lot, the less positive effect the sand has on the results
What do cold test results in corn tell me about my seed lot?
Vigor tests are used in two ways: to "predict" field emergence and/or to rank seed lots. Since field conditions vary greatly from field to field and from year to year, no test can predict how a lot will do in all situations. However, cold test results typically correlate well with field emergence for most lots.
Tray (Iowa) cold tests correlate best with unfavorable conditions while saturated cold test results correlate better with even less favorable field conditions. A 82% tray cold test result is usually considered to be the minimum acceptable for marketing a corn seed lot.
Is a cold test the preferred method for determining soybean vigor?
No, we recommend using the accelerated aging (AA) test. Because the cold test does not typically stress soybean seed much. Even though you would expect soybeans to be more sensitive to cold than corn, they don't actually seem to be. Another problem with cold tests on soybean seed is that some years, there are a few lots that experience decayed unifoliate leaves in the cold test and can which give lower than expected results. Extremely dry seed (below 10%) can result in rapid imbibition (water uptake) damage in the cold test. There is less chance of this in the AA test as water vapor gradually hydrates the seeds.
Why do I sometimes get high warm results and low cold results?
In general, carryover corn seed that is stored in cool, dry conditions maintains its viability and vigor well. Seed that is of low vigor or stored in less favorable conditions can be expected to experience a drop in vigor from year to year (or even month to month). A warm germ exposes the seed to "ideal" conditions. A seed lot with little mechanical or fungal damage or dead seed after harvest would be expected to maintain its viability fairly well when stored correctly. But when the seed is stored in less favorable conditions, the seed ages more quickly and cannot tolerate the stressful conditions of most vigor tests
How do saturated cold results compare with regular cold results?
Usually saturated cold results compare well with cold test results. However, at times they are markedly different. It can be beneficial to keep track of how a particular testing lab typically does on various tests. Once you see how their tests compare to each other (germination vs. cold, cold vs. saturated cold, etc), then the results will be more useful in determining the true viability and vigor of a seed lot. The saturated cold test is often considered to be a more severe test, but studies we have done comparing lab results to the field (different planting dates and conditions) show both tests correlating well with typical spring planting conditions.
What is an acceptable soybean accelerated aging (AA) result?In general, we advise that an AA result should be within 15% of an acceptable warm germ. What is acceptable varies from person to person, but most consider a 90% to be the minimum acceptable soybean germ most years. There are years when short supply of soybean seed can prompt the sale of lower germinating seed lots. But in a normal year, a 75% AA would be at the low end of a desirable AA results.
Why do I sometimes get higher soybean AA results than warm germination results?
There are two possible explanations: In seed lots with many seeds that have a light amount of Phomopsis on cotyledons, the AA test reduces the harmful effects of the Phomopsis because it does not stand up well to the hot, humid conditions of the AA chamber. Seed with a heavier amount of Phomopsis have already had the damage done.
Some lots (especially of large-seeded edible soybean seed ) can have problems taking up moisture on Kimpak®. Gradual uptake of water during the aging period of the AA test and covering the seed with moist sand following the aging period can help some lots
How can the Tetrazolium (TZ) test be utilized?
To check the viability of a seed sample in less time than a germination test (two days versus five days or more).
—To estimate the vigor of a sample of corn seed.
—To diagnose a problem seed lot (mechanical, fungal, or dryer damage or damage from maturing in the field.
—To check the viability of ungerminated seeds in a warm germination test.I
Can tetrazolium results be used for labeling?
Tetrazolium (TZ) results usually correlate well with warm germ results. However, they can be markedly different, especially in seed lots with fungal problems. The presence of fungi can be detected in a TZ test, but since the TZ test is a snapshot of the seed at about two days, it cannot detect how much the fungi will develop and hurt the seed by the end of the germination test. Labeling using the TZ test is not allowed except in a very few instances.