Understanding Your Seed Test Results


What the seed labs want you to know

Russell Trischuk, M.Sc.


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So there it is, the report from the seed lab just showed up in your mailbox. You open it and there you see about as many numbers as a comprehensive blood test. You understand some of the results, such as germination and disease, but you’re a bit unsure of the rest. “Don’t worry, you are not alone,” says Bruce Carriere, founder of Discovery Seed Labs. Carriere routinely runs a training seminar, fittingly named “Seed School”, for many growers and retailers who want to know more about their seed test results.

 

Most growers, who send in a seed sample for analysis to seed labs such as Discovery Seed Labs, are typically looking to understand a few key parameters about their sample. These include information on germination and disease, but there are several other analyses conducted that mean as much if not more that those key tests. “Having a greater understanding of what all those numbers mean is an excellent advantage to the grower,” says Carriere. After listening to Carriere talk about testing, it was apparent that growers would be interested. In the following paragraphs, I share what we’ve learned about seed tests to help growers better understand what they mean and the advantages they can have for their crops.

 

CFIA and other Accreditation

In order to operate a professional seed analysis facility, some form of accreditation is always required. Typically this accreditation comes the Canadian Food Inspection Agency, but not all seed labs have CFIA accreditation. To gain CFIA accreditation a seed lab must be trained to run and utilize CFIA seed analysis protocols to analyze samples for certain parameters. You may have noticed that not all analysis listed on reports are accredited. This doesn’t mean that they are not quality analysis; it only means that that specific analysis is not a CFIA-supported analysis. All CFIA-supported analyses are used as grading factors, due to international export requirements.

 

Germination vs. Vigour

The germination rate of your seed sample is probably the primary reason why you send a seed sample in. You plan on using it to determine which seed lots to retain for seeding purposes and which go to market. Unfortunately, a standard germination test can give you results that are misleading, as the standard test is specifically designed to coax every bit of life out of a given seed by giving it the most ideal conditions to grow. Unless you plan on planting your crop in petri dishes on moist paper towel this upcoming season, you may want to defer to the vigour results instead. A vigour analysis, unlike a standard germination test, is designed to impose a controlled level of stress on the seed, giving a more accurate indication of what you could expect to see in an actual cropping system. The test most commonly used is referred to as a cold saturation test, and this test exposes the seeds to an increased water and reduced temperature regime during the germination assay. The specific intention here is to kill or damage any seedlings that may arise from weak seed. In most instances a seed sample will see an 8% to 10% reduction in germination when compared to a standard germination test. When making the decision of which seed lot to keep and which to sell, it is best to take both these analyses into consideration. Here is an example of the type of data you can get from these two analyses and how you should use it to your advantage.

 

Seed Lot A – 95% Germination 90% Vigour – Strong seed lot; can seed at the recommended rate and in all conditions.

 

Seed Lot B – 95% Germination 80% Vigour – Average seed lot; ideally you would wait to sow into warmer soils or increase seeding rate to compensate for 20% reduction in vigour in cold soils.

 

Seed Lot C – 95% Germination 60% Vigour – Best to sell this seed to a grain handler/elevator, or if forced to use this seed, double the seeding rate and only sow into warm soils.

 

Notes Section

Regardless of the seed analysis certificate, there will always be a free-form section in which the analyst has put comments they want the grower to know. Pay particular attention to this section, as it will always contain important information that will help you understand your results.  Listed below are some common things that can be found in this Notes Section.

 

Abnormal and Dead Count

Within a germination analysis, an additional metric you may notice are that the number of dead and abnormal seedlings will be given a score. A dead seed count is pretty self-explanatory, but what is an abnormal seedling? An abnormal seedling is a seedling that initiates the germination process but due to a deficiency or physical damage will not produce a viable plant. An abnormal seedling will exhibit an abnormal morphology, relative to a normal seedling, and as a result will receive such a score. An example of an abnormal seedling would be a seedling that has a larger shoot than root after a few days of germination, whereas a normal seedling should have a root system that is 1.5 to 2 times larger than the shoot. The ability to pick out an abnormal seedling is difficult to do, and should be left to an accredited seed analyst who has received professional training.

 

Physical/Mechanical Damage

This is exactly as it sounds. It’s damage caused to a seed that has had some form of physical stress imposed on it that leads to abnormal germination or death. Causes of this type of damage can occur at any time when the seed is physically handled including harvest, augering, falling to the bottom of a bin, etc.

 

TIP: Don’t use the bottom 15 cm of any bin for seeding, as it will have an extremely high number of damaged seeds from the drop out of the auger.

 

Chemical Damage

The majority of chemical damage that is detected in a seed analysis is the result of exposure to the non-selective herbicide, glyphosate. This damage typically occurs in lentil, pea and wheat seed samples. In instances where growers use glyphosate to desiccate their crop prior to harvest, a chemical damage rating can occur. Contrary to common belief, if a grower applies glyphosate at the correct timing (plant must no longer be cycling nutrients from roots to shoots, but rather from shoots to roots) a fine layer of the chemical adsorbs to the seed coat which has no effect on the seeds ability to germoinate. If put onto a petri dish for a germination analysis, the glyphosate resolubilizes, becomes active in the water and renders the seedling abnormal. If the seed is sown into a soil medium for testing, the glyphosate will resolubilize but is quickly adsorbed by the soil and rendered inactive. However, if you have not timed the glyphosate application properly and the plant is still moving water and nutrients into the seed, glyphosate will be translocated to the seed rendering it abnormal.

 

TIP: If you have used glyphosate to desiccate your crop, indicate it on your seed sample submission form, as your tests will be conducted in soil to ensure that your seed is not incorrectly assessed.

 

KNO3  Potassium Nitrate

KNO3  is the chemical formula for the salt, potassium nitrate. Potassium nitrate buffer is applied to seed to remove any dormancy that is still present within the seed. If you see this in your notes section, it means is that your samples were treated with this buffer to break its dormancy.

 

Clearfield®-Confirm

The purpose of a Clearfield-Confirm test is to make sure that the seed lot in question has not been co-mingled with non Clearfield seed and that the herbicide tolerance levels are high enough to ensure maximum effectiveness of the Clearfield herbicides.

 

Physical Purity

The physical purity analysis is conducted to detect the amount of off-type grain (e.g. durum in wheat) or weed seed in a given sample. Although this is a pretty self-explanatory analysis, the results are often confusing as it is reported in units that are not commonly used. The results of this assay are reported in the number of seeds per kilogram of seed, or in the case of smaller seed per 50 grams, which when translated into seeding rates can catch a grower by surprise. Here is an example of two physical purity results that demonstrates how the result can be accidentally misunderstood.

 

Sample A

Sample B

1 Cleaver Seed per kg of Wheat Seed

10 Cleaver Seeds per kg of Wheat Seed

Seeding Rate 1.5 bu/ac = 41 g

Seeding Rate 1.5 bu/ac = 41 g

41 Cleaver Plant Per Acre

410 Cleaver Plants Per Acre

 

 

Fusarium graminaraeum  vs. Total Fusarium

With the movement of Fusarium Head Blight (FHB) from Manitoba westwards, one of the key analyses conducted on cereal samples is for the presence of this disease on the seed. The species F. graminareaum typically has received most of the attention, as it is the species responsible for the production of the vomitoxin, deoxynivalenol or DON.  As a result, a large number of seed samples come in for analysis for this single species of Fusarium. While understanding the levels of this pathogen in your seed sample is important, a grower should really consider testing his grain sample for all species of Fusarium.  All species contribute to the overall level of infection of FHB and are not differentiated when a sample is taken by a grain purchaser, since all lead to FDK (Fusarium damaged kernels). This is more important when a grower will be using the seed for a following year’s crop, since seedling blight caused by Fusarium-infected seed can lead to future outbreaks of FHB. This can be managed properly with clean seed and the use of Charter® RTU or Insure™ Cereal* (available 2013*) seed treatments. For an example of the acceptable levels of Fusarium in a sample used for seed, consider the following table from Discovery Seed Labs.

 

f. Graminearum (with none in area)

Crop

No Treat

Treat

Get Rid of

Barley

0

0 - 0

> 0.0

Wheat

0

0 - 0

> 0.0

Durum

0

0 - 0

> 0.0

f. Graminearum (with some in area)

Barley

0

0 - 2

> 2.5

Wheat

0

0 - 3

> 3.5

Durum

0

0 - 2

> 2.5

 

Total Fusarium

Crop

No Treat

Treat

Get Rid of

Barley

0 - 7

7- 13

> 14

Wheat

0 - 7

7- 13

> 14

Durum

0 - 7

7- 13

> 14

Cochliobolus

Barley

0 - 5

7- 13

> 14

Wheat

0 - 5

7- 13

> 14

Durum

0 - 5

7- 13

> 14

 

Ascochyta, Botrytis and Sclerotinia

In pulse samples, the level of these three, common pulse diseases are available in a seed analysis. In the instance of Ascochyta the levels analyzed are used for two purposes. First, it is a CFIA certified analyses and is used in the grading process. Second, this analysis can be used to gain an idea of whether or not a specific seed lot should be saved for use as seed. In most instances, with regards to Ascochyta and Sclerotinia, the level of disease detected in the seed is strongly correlated to the number of seedlings that will be infected with seedling diseases. This information can be used to decide (in combination with germination and vigour assays) whether or not a seed lot can be retained for use as seed.

 

When looking at the Botrytis levels in a seed lot, one must not be lulled into a false sense of security when low levels of Botrytis (e.g. 1.5 – 2%) are indicated. The spread of this disease occurs after the seedlings have emerged, and a single infected plant in a row can result in the rapid and mass infection of the entire row. A single infected plant, once weakened by the disease, will fall over and contact the seedling next to it, spreading the disease as a result of the contact which can then continue down the entire length of the row. Please refer to the following tables, supplied by Discovery Seed Labs, for a guide to acceptable levels of these diseases, for use as seed.

 

Ascochyta

Crop

No Treat

Treat

Get Rid of

Chickpea

0

0 - 3

> 3

Field Pea

0 - 7

7 - 14

> 15

Lentil

0 - 2

2 - 5

> 6

Botrytis & Sclerotinia

Chickpea

0 - 7

7 - 12

> 14

Field Pea

0 - 7

7 - 12

> 14

Lentil

0 - 7

7 - 12

> 14

 

When to Test and When to Re-Test Your Seed

One of the most common questions about seed tests is when to conduct the seed analysis test. The answer to this question is simple; as soon as it comes out of the combine. The primary reason a grower tests the quality of his or her seed is to determine whether or not to retain it for seed or to sell it and this is the best time to make that decision. Typically the quality of the seed does not change as a result of storage over the winter.

 

So when should a grower consider re-testing their stored seed lot? As long as seed has been put into storage at the proper moisture and temperature levels and is stored and managed properly, there will be very little change in the seed lot. However, if the seed has been stored under non-ideal conditions such being placed in a bin at high moisture levels, at too warm temperatures and not managed properly (not turned over, or aerated, or dried, etc.), a grower should consider re-testing the seed lot for germination and vigour. Since these conditions are not ideal for the storage of seed, there is a good chance that changes have occurred in the seed sample over the winter. Levels of disease however, will not change as a result of improper storage and need not be re-tested after overwintering.

 

I hope the information provided in this article was both informative and useful.  If you have any further questions regarding any of the results you have observed on your seed analysis certificate please feel free to contact me, Russell Trischuk, Technical Development Specialist with BASF or Bruce Carriere, President and Owner of Discovery Seed Labs.

 

* Pending registration by the PMRA.