Testing conducted at the Tree Seed Centre follows rules set up by the International Seed Testing Association (ISTA), an organization established to promote the production of high quality seed world wide. ISTA rules and procedures outline a set of methods, calculations and standards for sampling and determining moisture content, percent purity, germination and seed weight. The Association of Official Seed analysts (AOSA) is another organization involved with trying to establish uniformity and accuracy in methods, results, and reports in seed testing. These groups are currently trying to harmonize their rules. ISTA has a Forest Tree and Shrub Seed Committee and AOSA has a Tree, Shrub,and Native Forb Working Group that address issues specific to forest tree seeds.

Seedlot tests are of two types : Standard (STD) and Quality Assurance (QA). Standard tests use seed samples that are representative of the entire seedlot and are the only tests that will be displayed on SPAR. Quality Assurance tests are those tests performed on a portion of a seedlot, a specific point in processing, or on a specific request (i.e. moisture content and germination for sowing requests). Some QA tests may be the same as a STD test, but the material will be sampled from only a portion of the seedlot and the result is not used to characterize the seedlot. Further information on QA tests and summary results can be found in the Cone and Seed Improvement section.

Seed sampling

To obtain an accurate test result one must have a representative sample of the seedlot - a test result is only as good as the sample taken! Seedlots are sampled for new tests after the seedlot has been blended to ensure homogeneity. The sampling scheme we use is based on the ISTA Rules which specify, based on seedlot size, how many containers should be sampled and how many samples per container should be taken from a seedlot. These samples are considered primary samples and are the point at which seed is withdrawn from the seedlot. These samples are combined and thoroughly mixed to form the composite sample. Sub-samples are randomly taken from different areas of the composite sample to obtain the appropriate submitted sample size with excess seed being returned to the seedlot. The working sample is a sub-sample of the submitted sample on which the seed tests are performed. A diagram illustrating the sampling methodology and standard testing workflow follows:

New seedlot testing

New seedlots must pass some basic testing requirements before they can be placed into freezer storage. The submitted sample for moisture content is made up of two working samples for the two replications of the test. It is critical to determine that the moisture content is within the 4.0 to 9.9 % range to ensure seed can be safely placed into freezer storage. The second submitted sample is divided into two working samples and used to test the purity of the seedlot. The seedlot must be above 97% pure seed by weight, this ensures efficient seed storage and assists with nursery handling and efficiency. The moisture content and purity ranges are the physical quality parameters for a seedlot under the Chief Forester's Standards for Seed use. If a seedlot's purity is less than 97% or the moisture content below 4.0% or above 9.9%, additional processing is required to bring the seedlot to within these standards.

When the moisture content and purity tests are complete and accepted, eight working samples of 100 seeds are drawn for 100-seed weight from the pure seed fraction of the purity test. The seed weight test result is not placed on SPAR as the seeds per gram value that corrects for seedlot purity is more useful. One can convert between these variables using the following formula:

These 100-seed replicates are then used for germination testing performed according to the germination test types by species (see TSC test types). The germination capacity and germination rate are calculated for each seedlot test and an x-ray of one replicate is captured as a record of seed characteristics. For some species two germination tests types are performed with the superior test type receiving an A-ranked designation on SPAR. This A-ranked germination is used in potential seedling calculations. For further information on potential seedlings and sowing guidelines, see the following documentation (2007 MOF Sowing Guidelines).

If a request for use of the seedlot is received before germination testing is complete, a species average (SA) or client requested seedlot estimated germination (SE) is placed on SPAR and used to calculate potential seedlings and grams required. Please refer to the Species Averages Table for more information about average germination by species.

Retesting

Germination tests are repeated to maintain an accurate estimate of germination and estimation of potential seedlings in SPAR. The frequency is based on analysis of current and historical germination tests (see Cone and Seed Improvement) and results in species being retested at intervals of 18 months to 48 months. Retesting frequency and the types of tests performed depend on species and, in some cases,individual seedlot quality and use. Clients may also request more frequent seedlot retests on a fee-for-service basis.

Fungal assays

The focus of this program is to identify the presence and rate of infection of major seed-borne pathogenic fungi. Three fungi are considered seed-borne and potential pathogens: Caloscypha fulgens (CAL), Sirococcus conigenus (SIR), and Fusarium sp. (FUS). Not all seedlots are tested for all pathogens. A priority matrix has been established by seed pathologists and this along with collection method, seedlot performance, available balance, usage and concerns expressed by growers, processors, seed owners, and other clients are involved in selecting seedlots for fungal assays. The results of these tests are maintained on SPAR.

Quality assurance and research

The testing area provides a large amount of the support required in our Quality Assurance program. This involves germination testing of sowing requests, assessment of pellet quality and measurement of moisture content of cones and seed at various stages of processing or pretreatment. Testing also supports research trials at both a basic and operational level to address issues of importance to conifer seed science and technology.