The seed-testing laboratory determines the moisture content of a seed sample by means of two partial samples using the ‘dry box’ method. The sampling, type of crushing, drying temperature and drying duration are in accordance with the provisions stipulated by the International Seed Testing Association.
Determining Moisture Content
Purity Analysis
The purity analysis determines the weight percentages of both ‘pure’ and ‘undesirable’ seeds as well as of harmless impurities in a sample of 2500 seeds. The different species of ‘undesirable’ seeds and harmless impurities are identified and catalogued. In this way, we can ensure that the seed was grown and sorted in accordance with the desired or required standards.
Next, if the applicant so wishes, eight-times-one-hundred seeds in the ‘pure’ seed fraction are counted off and weighed, and the weight of one thousand seeds is then calculated.
In addition, the density of seeds of other species in a sample of 25,000 seeds is determined in terms of number. This analysis helps ensure that no undesirable (e.g. invasive or poisonous) plant species are inadvertently spread via seed.
The sampling, seed-purity assessment and analysis method are in accordance with the provisions and criteria stipulated by the International Seed Testing Association.
Viability Assay
The viability of seed can be determined by means of a tetrazolium assay. Use is made of this test inter alia when dormancy of the seeds of the tested plant species is suspected. This method is used in Agroscope’s seed-testing laboratory primarily in the case of freshly harvested barley. Here, rapid appraisal of viability before sorting is important, since the time available before sowing is very short.
Preparation of the test material, staining duration and assessment criteria are in accordance with the provisions stipulated by the International Seed Testing Association.
Germination Study
Germination is determined by means of a sample of four hundred ‘pure’ seeds under optimum stipulated germinating conditions. The seedlings which are to be rated as normal are catalogued at regular intervals. After the prescribed test duration, the abnormally developed seedlings as well as the ungerminated seeds are also determined. The test methods and evaluation of the seedlings are in accordance with the provisions and criteria stipulated by the International Seed Testing Association.
The cold test determines the germinating power of maize under difficult growing conditions.
In addition, the level of infestation of organically produced seed grain with snow mould (Microdochium nivale) is analysed and catalogued.
Authenticity Testing
The following methods can be used to determine the species or variety of a batch of seeds:
a) Fluorescence testing:
After germination under certain conditions, non-distinguishable ryegrass species (especially perennial and Italian ryegrass) can be assigned to their respective species on the basis of the reaction of their roots to fluorescence.
b) Electrophoresis:
With the help of electrophoresis, grain varieties and species can be distinguished on the basis of their different cereal storage proteins. To this end, the alcohol-soluble proteins in Triticum and Hordeum as well as the alcohol- or water-soluble proteins in Zea mays are extracted from the seeds and separated with the help of an electrical field into a typical banding pattern. These variety- and species-specific banding patterns are compared with those of the reference. This enables the purity and authenticity of Triticum and Hordeum varieties/species (A-PAGE) to be analysed. Electrophoresis (IEF) is used in maize hybrid-seed production to test whether fertilisation by the desired pollinator did in fact occur.
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