A Search for Seed Vigour Testing Solutions
The best way to compare and evaluate the maximum potential of a seed lot is with a germination test; however, this test doesn’t often predict emergence and performance under a wide range of conditions. Seed vigour is an attempt to evaluate the activity and performance for seed lots of acceptable germination.
There are many ways to evaluate seed vigour. This has created some confusion for companies, growers and end-users as to what the laboratory results mean and how to interpret them. Fortunately, much work has been done by the International Seed Testing Association’s (ISTA) Vigour Committee. Validated tests exist for many species. Most recently at the ISTA Congress in Edinburgh, Scotland, Kabuli chickpea (Cicer arietinum) was added to the conductivity vigour test, which already included bean (Phaseolus vulgaris), garden pea (Pisum sativum) and soybean (Glycine max). Additionally, oilseed rape/Argentine canola (Brassica napus) was added to the radicle emergence test, which had previously only contained corn (Zea mays).
In Canada, the demand for a uniform validated vigour test in cereals has been a growing concern for commodity farmers, seed growers, agronomists, crop advisors and seed companies. There are no validated tests for common wheat, durum wheat, barley, oat, rye and triticale. Two years ago the Commercial Seed Analysts Association of Canada formed a Vigour Committee to address these concerns. As a CSAAC Vigour Committee member, I had the opportunity to attend the ISTA Congress and talk with ISTA vigour experts about our issues.
People from less harsh climates have greater concerns with vigour in high value vegetable and flower species, as well as corn, so this is where they tend to spend their research dollars. One of the great Canadian challenges from a seed testing standpoint is that our cereals often have dormancy issues that do not exist in other parts of the world. Many times cold tests and aging-type tests show low results due to a high percentage of dormant seeds, not low vigour.
A Tetrazolium test for seed viability is often used for vigour testing in South America, which allows every seed to be evaluated regardless of dormancy, as the seed does not need to sprout for the test. The problem here is that it’s very time consuming and requires an experienced seed analyst. Can you say expensive? The conductivity measures leachates that come out of the seeds. Conductivity tests do not relate to field trials in grasses, such as cereals, likely because there is so much material that is not alive (the starchy endosperm) attached to the seed.
The CSAAC Vigour Committee is a determined group and has some thoughts. Radicle emergence has gained recognition around the world as it is replicable and relatively simple to perform. It does, however, require much greater precision in temperature, timing and training than a germination test. Even the slightest change in time and temperature can give an inconsistent result. In the validated test for corn, seeds are planted at 20 C, and at 66 hours, seedlings with a 2-millimetre radicle are counted. This results in proven valuable information on the ability of the seed to produce plant stands. There is some work that shows great promise in the field using this test in other wheat producing areas of the world. If we can get over the challenges of the dormancy factor, CSAAC would like to engage institutions to help study the value of this test.
For more information, please contact Morgan Webb or Vigour Committee chair Krista Erickson. Contact details are available online at seedanalysts.ca.