Seed Quality

Table of contents

    Important tips for best management

    • Seed quality is a major factor in stand establishment and yield potential. Certified seed with high germination tends to emerge faster and more evenly under a wider range of conditions than seed with lower germination rates. [1] [2]
    •  Hybrid seed also tends to provide advantages over open pollinated varieties, including plant establishment and growth rate as well as final seed yield. [5]
    • For a comparison of new varieties, try the Canola Performance Trials tool.


    Seed vigour 

    Vigour is defined as those seed properties that determine the potential for rapid uniform emergence and development of normal seedlings under a wide range of field conditions. Germination analysis is the only Canadian approved indicator of seed vigour. Seed with high germination will usually have high vigour. AAFC research shows that seed lots with germination above 95% had the highest seedling establishment in early and late May plantings. [2]

    As outlined in the Canada Seeds Act, certified No.1 canola must have 90% germination and certified No.2 canola must have 80% to 89% germination. Seed must meet these standards at the time of sale, no matter when that seed was grown. These standards also apply to seed that is returned and then resold the following season. Germination tests have to be updated, and growers can ask to see the seed analysis.

    Standardized germination tests, as outlined by the Canadian Food Inspection Agency (CFIA), measure the percent of germinated seeds after seven days under ideal conditions (e.g. moist blotter, warm temperatures). If seed makes a late surge, tests can be extended to 10 days, but this should be noted on the analysis report.

    Some labs will also provide a four- or five-day test. A seed lot that reaches 90% germination within that time period tends to be more vigourous. [3]

    Seed lots with low vigour will result in poor establishment under adverse seedbed conditions such as low temperatures and crusting.

    Accurate seed vigour assessment requires an understanding of the potential causes of reduced initial seed quality or seed deterioration following harvest for each seed lot. Factors that could negatively influence seed quality may include:

    • unbalanced or inadequate nutrition
    • diseases (e.g. alternaria black spot)
    • swathing too early [4]
    • weathering during ripening
    • physical seed injury during harvest and transport
    • improper storage and overall age


    About a dozen Prairie-based seed labs offer canola vigour tests in addition to standard germination tests, but the Canada Seeds Act does not include a national vigour standard for canola seed, and the CFIA does not have an approved test. Here are the tests used:

    1. Cool stress tests put seed on a moist blotter at 7 or 8 °C or less for two weeks or so and then count germinated seeds.
    2. Prechill tests put seed in saturated potting soil at 5 °C for a week then warm it up for four days before counting germinated seeds.
    3. Electrical conductivity tests identify seed coat quality and the extent of dead tissue in the seed. Seed lots with low conductivity are more vigourous than seed lots with high conductivity.
    4. Controlled deterioration raises seed moisture to 20% then holds the seed at 45 °C — before putting it through a regular germination test. Controlled deterioration is the only canola vigour test with a standard procedure validated by the International Seed Testing Association.


    Protocols for each test often vary from lab to lab. One lab’s cool vigour stress test may keep canola at 7 °C for 14 days. Another lab may test at 8 °C for 12 days. For labs that offer prechill tests, one may turn the temperature up to 30 °C for five days following a seven-day cold stress test, while another alternates between 15 °C and 25 °C for four days after seven days in cold soils. Even the terminology is inconsistent. A lab may offer a prechill test but call it a “cold test” or “saturated cold test. 

    For these reasons, growers are encouraged to find a lab they are confident in and then use if for all their seed testing. They should not try to compare results from lab to lab, even if the labs are doing the same type of test.

    Seed Size

    Larger canola seed produces larger seedlings and higher yields[1], although the yield benefits may plateau once seed reaches 4-5 grams per 1,000 seeds. [3b] Many canola seed lots sold today, especially hybrid seed, are in that size range or larger, so it is uncertain whether seed size will influence yield the way it has in past studies.

    The larger seed size of hybrid varieties does result in a small increase in emergence percentage compared to smaller open pollinated (OP) varieties. For example, in three separate experiments conducted by AAFC researchers, canola hybrid varieties tested had 25% to 50% larger seed than OP varieties. [6] [7] [8] Yet, the emergence percentage based on live seed planted only improved 5% to 6% over the OP varieties. Therefore, to achieve similar plant densities, hybrid seeding rates in lb/ac would have to be higher than OP because the increase in seed size is much larger than the increase in emergence percentage.

    The overall body of research on the effect of canola seed size on subsequent yield has been contradictory. In a review of seed size research on the Prairies, larger seed produced higher yield in five of 27 site years. [10] In some cases, larger seed produced more vigourous seedlings, but this advantage wasn't carried through to seed yield. There is good evidence that large seed produces seedlings more resilient to flea beetle attack and thus is higher yielding in situations with flea beetles.

    Seed source

    Canola seed comes in three types: hybrid, synthetic and open pollinated (OP). Hybrid seed prodused by a controlled cross between two parent lines: a sterile male or female line (a plant that lacks viable pollen and therefore cannot self-pollinate or pollinate neighboring plants) and a pollinator (male) line that pollinates the female block.  The male line is removed after pollination because it can self-pollinate and would be a source of non-hybrid seed.  Thus all seed from the female has been pollinated by only the male line and was from two parents — it’s a hybrid — and with that “heterosis” often comes added vigour and yield. Seed companies research thousands of parent lines and combinations to find ones that provide the greatest heterosis.

    To be called hybrid, a seed lot has to contain a minimum of 80% hybrid seeds, based on Canada Seeds Act standards. Higher levels of hybrid seed in a lot will ensure more consistent and predictable performance. Therefore, companies will often take steps beyond simply removing the male lines following pollination in order to ensure hybridity levels well above the minimum standards. This improves the quality and predictability of a hybrid seed lot, but adds to the cost of hybrid seed.

    In contrast, synthetic seed is produced by mixing together two or more parents in a blend, seeding this blend and collecting all the seed produced.   Since this allows self-pollination and cross pollination between the same or different parents, the result is a mixture of hybrid and non-hybrid seed. In some B. napus synthetics, a male-sterile line is used in the blend to reduce the proportion of self-pollinated seed. Synthetics must achieve at least 70% hybrid seed. Because this is an easier method of seed production, synthetics don’t have the same underlying costs of production.

    OP varieties are produced from a single parent. With good isolation from contaminating sources of pollen, the seed produced from an OP line will be genetically similar to the parent. They are relatively easy to produce, but do not have the heterosis associated with seed produced by crossing two distinct parent line.

    Important factors to consider when choosing seed: 

    • Will the variety grow and mature uniformly within the expected growing season?
    • Does the variety have resistance to local diseases?
    • Does the variety have herbicide-tolerant traits that match the anticipated weed spectrum?
    • Does the seed lot have high germination? And when was the last germination test done?
    • Does the seed lot contain weed seeds not found in your area?
    • Is the seed lot pedigreed to ensure true varietal characteristics?
    • Do the seed bags show signs of proper storage?
    • Does the seed treatment appear uniformly applied?
    • How consistent did the variety perform in trials under various environmental conditions? 


    Canola seed quality is affected by the environment under which it was produced. Purchase plump, well matured seed from known suppliers.

    How to preserve seed quality

    No.1 certified canola seed stored at 2 °C or cooler and at less than 8% moisture will maintain its minimum 90% germination for at least 18 months. [9] Canola stores best at a cool even temperature and at a dry non-fluctuating humidity. Keep rodents and insects away from seed bags.

    Blackleg ratings

    Blackleg resistance is based on a percentage of Westar, an older variety known to be susceptible to all races of blackleg. Here is how the rating is measured:

    For each test entry in the registration co-op trials, 25 plants will be assessed from each of a minimum of four replicates of a naturally infected or artificially inoculated field test. Plants in blackleg trials must be rated at plant stage 5.2 on the Harper and Berkenkamp scale. Plants are cut open at the site of the stem canker, and rated as follows:

    0 - no diseased tissue visible in the cross-section

    1 - Diseased tissue occupies up to 25% of cross-section

    2 - Diseased tissue occupies 26-50% of cross-section

    3 - Diseased tissue occupies 51-75% of cross-section

    4 - Diseased tissue occupies more than 75% of cross-section with little or no constriction of affected tissues

    5 - Diseased tissue occupies 100% of cross-section with significant constriction of affected tissues; tissue dry and brittle; plant dead.


    Westar must be included as an entry in each blackleg trial. Tests shall be considered valid when the mean rating for Westar is greater than or equal to 2.6 and less than or equal to 4.5. In years when there is poor disease development in Western Canada the Western Canada Canola/Rapeseed Recommending Committee (WCC/RRC) may accept the use of data from trials with a rating for Westar exceeding 2.0.

    Ratings are converted to a percentage severity index for each line, and the following scale is used to describe the level of resistance:

    Classification Rating (% of Westar)
    R (Resistant) <30
    MR (Moderately Resistant) 30 – 49
    MS (Moderately Susceptible) 50 – 69
    S (Susceptible) 70 – 100


    The blackleg disease organism has diverse genetics that can change in response to selection pressure.  New races of blackleg are being found on the Prairies and variety resistance may not be equally effective in all fields.  Continual planting of the same variety or blackleg resistance gene in short rotation will increase the probability (and likely the rate) of resistance breakdown.


    Seed testing and certification

    The blue certified seed tag assures that seed purchased meets the minimum standards for purity and germination, as outlined by the Canada Seeds Acts.

    The Canada Seeds Act (http://laws-lois.justice.gc.ca/en/S-8) designated the Canadian Seed Growers' Association (CSGA) to be the sole seed pedigree agency for most crops in Canada. CSGA establishes genetic standards and ensures that these standards are maintained.

    Approved crop inspectors inspect pedigreed seed crops and report to the CSGA on the conditions of these seed fields. The inspectors verify the variety sown, previous land use, isolation, any weed infestations, plants of other crop kinds, and the degree of contamination with other varieties or off-types. Crops that meet the standards are issued a crop certificate by the CSGA.

    A licensed grader then inspects the seed from those fields to determine the grade under the Canada Seeds Act. Factors assessed include germination, freedom from weed seeds, sclerotia bodies, other Brassica crop kinds and overall quality.

    Certified seed is the class recommended for commercial canola production. Only one generation of certified seed is allowed. Seed produced from a crop grown from certified seed is no longer pedigreed and it is illegal to advertise or sell it under a variety name. Such seed is classed as "common seed."

    Since B. napus canola cross pollinates about 25% of the time, the more generations removed from the original breeder seed, the greater the likelihood that outcrossing will have occurred. Therefore, some of the seed may no longer carry the genetically superior qualities. This is especially true for hybrids. Second generation seed (F2) from certified hybrid seed will not have consistent characteristics throughout the seed lot. Herbicide tolerance, maturity and oil quality traits, among others, will be more variable and less predictable in the F2 seed. The proportion of the plants exhibiting these inferior traits in the F2 population is large enough to also result in significant yield reduction on average. [7] Note that use of F2 seed is illegal as per agreements signed with the seed companies.

    Certified seed provides an extremely close copy of the genetic characteristics of the original breeder seed, as well as strict standards for genetic purity, weeds (especially wild mustard and cleavers) and high germination.

    Certified seed has a low tolerance for contamination by other varieties. The current tolerance is 1.5 plants for every 10,000 plants. Although this tolerance is very low, the number of off-types or other varieties in a field planted with certified seed could be noticeable. For example, a stand of 100 plants per square metre (10 plants per square foot) with a maximum contamination of 1.5 per 10,000 in the seedlot, will create roughly 160 off-types per hectare (65 per acre). The off-types could be herbicide-tolerant (HT) varieties in a conventional variety. This explains why some growers find HT volunteers after seeding a conventional variety from a certified seedlot on land that was not previously seeded to HT varieties or close to a field of HT canola.

    Certified seed standards include maximum tolerances for noxious weed seeds, secondary noxious seeds, other weed seeds, and seeds from other crops. Growers can ask the seed supplier for a weed seed analysis of the seed lot. Talk to your seed supplier well in advance so that the information is available before purchase. Access to the results of such an analysis done by an accredited seed laboratory is a right for all seed buyers as specified in the Canada Seeds Act. This information can help growers avoid the introduction of new weeds to their farms.

    Subtopic: Plant Breeders' Rights

    Plant breeders incur substantial costs to develop valuable varieties and thus they wish to protect them from pirating. Canada's Plant Breeders' Rights Act enacted in 1990 (http://laws-lois.justice.gc.ca/en/P-14.6/fulltoc.html) allows plant breeders to control the seed of new varieties that they develop and collect royalties on them for 18 years. Similar to a copyright or patent, Plant Breeders' Rights (PBR) protect the research investment made to develop new crop varieties. Proponents of PBR contend that plant breeding is the most cost-effective way to achieve increases in yields, quality and disease resistance.

    PBR protection is an exclusive right to sell and produce the seed in Canada. Further sales for propagation purposes are not allowed without the approval of the breeder. Farmers are allowed to save some seed for their own replanting purposes, but sales to other individuals or corporations are prohibited. Note that PBR does not invalidate legal agreements with seed suppliers that prohibit saving seed for replanting.


    References 

    [1] “Effects of seed size and seed weight on seedling establishment, vigour and tolerance of Argentine canola (Brassica napus) to flea beetles, Phyllotreta spp.” R. H. Elliott et al, Canadian Journal of Plant Science, 2007. Under controlled environmental conditions, leaf area, shoot weight and biomass of seedlings from large and very large seeds were 1.3 to 2.0 times greater than those of seedlings from small seeds, the study concluded. Large seed also produced higher yields in this study. But at that time, large canola seed was 3.6 to 4.4 grams per 1,000 seeds.

    [2] “Effect of germination, seed weight and vigour index on the performance of Argentine canola in cool and warm soils,” R.H. Elliott, Saskatoon Research Centre, Agriculture and Agri-Food Canada, CARP Project # 2003-02-01-19.

    [3] Personal communication with R.H. Elliott. (3b.) AAFC’s seed size studies noted in Footnote 1 have not been repeated to see if the benefit for stand establishment and yield potential continues for seed larger than 4.4 grams.

    [3b] R.H. Elliott, the lead researcher in this work, speculates that once seed reaches a level of 4-5 grams per 1,000 seed weight (TSW), these benefits may plateau.

    [4] “Effect of seeding date and swathing time on seed quality and the performance of open-pollinated Argentine canola,” R.H. Elliott, Saskatoon Research Centre, Agriculture and Agri-Food Canada, C. Vera, Melfort Research Farm, CARP Project # 2003-02-01-19.

    [5] “Response of hybrid canola to seeding rate, fertility and time of weed removal.” George W. Clayton, K Neil Harker, Adrian M Johnston and Kelly T. Turkington, 10th International Rapeseed Congress.

    [6] Seeding rate, fertilizer level and disease management effects on hybrid versus open pollinated canola (Brassica napus L.) Brandt et al., 2007, Can. J. Pl. Sci. 87:255-266;

    [7]Comparison of certified and farm-saved seed on yield and quality characteristics of canola” Clayton et al., 2009, Agron. J., 2009 101:1581-1588;

    [8]Seeding rate, herbicide timing and competitive hybrids contribute to integrated weed management in canola (Brassica napus)” Harker et al., 2003,Can. J. Pl. Sci. 83:433-440

    [9] “Effect of storage conditions and seed quality on germination and seed grade of open-pollinated and hybrid Argentine canola.” R.H. Elliott, Saskatoon Research Centre, Agriculture and Agri-Food Canada, CARP Project # 2003-02-01-19.

    [10] Murray Hartman, oilseed specialist with Alberta Agriculture and Rural Development. Personal communication.