Physical purity testing
What is physical purity? Physical purity testing quantifies the weight percentages in a seed lot of
- Pure seed
- Other crop seeds
- Weed seeds
- Inert matter (other matter than seeds: broken seeds, chaffs, sterile florets, stems, and stones)
All species of seed and all types of inert matter present shall be identified as far as possible. Physical purity testing is regulated by International Seed Testing Association (ISTA) rules.
Physical purity imaging
While physical purity imaging is not the same as physical purity testing then it quantifies similar properties of a seed lot in order to:
- work as an aid in ISTA regulated physical purity testing,
- estimate physical purity in unregulated seed analysis,
- optimize seed processing by choosing the right kind of processing equipment, adjust the equipment, and predict the yield of a given seed lot,
- integrate physical purity tests with destructive tests where a fraction of the pure seeds are needed e.g. germination tests, vigor tests, and seed health tests. The sampling of pure seeds may be done by robot picking.
Physical purity imaging can in principle measure samples in a similar way to physical purity testing. From an industry and cost point of view there are, however, important advantages to harvest from this new non-contact sensing technology if we
- measure number percentages instead of weight percentages. Number percentages are already used in other parts of seed testing like germination, vigor, and seed health testing and may make sense for physical purity as well. Optical weight estimates are also possible based on size (area, volume) and a density assumption for each fraction.
- measure on one side of the seed only. This will make the mechanical presentation of seeds much easier, and will allow larger seed samples to be handled more robustly. Larger sample sizes will reduce the sampling variation and balance the loss of information in one-sided analysis.
What is genetic purity? Genetic purity refers to how genetically pure a seed sample is in terms of seed variety or species and how true the phenotype is to its mother at all stages of reproduction. Genetic purity is used to maintain a variety from generation to generation, and in the management of genetic resources e.g. in genebanks. Some applications of genetic purity imaging with Videometer technology are shown in:
- Hansen, M., Hay, F., & Carstensen, J. (2016). A virtual seed file: The use of multispectral image analysis in the management of genebank seed accessions. Plant Genetic Resources, 14(3), 238-241. doi:10.1017/S1479262115000362
- LIU, C., LIU, W., LU, X., CHEN, W., CHEN, F., YANG, J., & ZHENG, L. (2016). Non-destructive discrimination of conventional and glyphosate-resistant soybean seeds and their hybrid descendants using multispectral imaging and chemometric methods. The Journal of Agricultural Science, 154(1), 1-12. doi:10.1017/S0021859614001142
VideometerLab - the leading seed imaging instrument
VideometerLab is a spectral imaging instrument that combines spectroscopy, imaging, and machine learning into a very strong analysis technology that is rapid, non-destructive and versatile. Further, the VideometerLab has been used and optimized for seed imaging over the last decades, and there is a vast amount of seed specific scientific literature.
VideometerLab can analyze a sample in two ways:
- Manual: Petri dish up to 90 mm diameter, analysis time is 10-20 seconds per sample.
- Automation: an autofeeder option allows to feed a larger seed sample on to a conveyor belt that automatically brings the sample to the instrument, analysis time for e.g. corn is 4-5 minutes for 300 gram.
VideometerLab can provide a very versatile measurement in the same workflow:
- Physical purity
- Thousand seed weight (TSW)
- Screen size of pure seeds
- Mechanical damage (cracked, broken, skinning)
- Insect damage
- Molds and other pathogens
- Phenotypic traits on pure seed fraction correlated with e.g.
VideometerLab can work with a local database or a cloud database of virtual seeds in order to have an effective way to store phenotypes and phenotypic variation within each crop.