Seed classification is based on the number of generations from pre basic seed and on the observed quality of seed plots and seed lots.
Various names are used to classify seed: a.o. breeders seed, pre-basic seed, basic seed, super-elite, elite, foundation seed, certified seed, approved seed, registered seed, commercial seed. These names are neither uniformly used nor are they often always clearly defined.
In this programme we use:
In generative multiplied crops there is an emphasis on the number of generations for classification of the seed, whereas in vegetative multiplied crops in this respect the contamination of the seed with diseases is more pre-dominant.
- pre-basic seed
- basic seed (1 and 2)
- certified seed (1 and 2)
- commercial seed
Number of generations and contamination with diseases
Seed becomes more and more contaminated (degenerates) with diseases, each time it is multiplied.
The degeneration rate caused by pathogens depends on:
1) infection sources present
2) number of vectors which transmit pathogens
3) plant resistance to pathogens
Tolerances for diseases are specified for each generation.
In the first generations the tolerances are low (or zero). The virus tolerances in the lower generations are higher. For quarantine diseases (e.g. ring rot and brown rot) the lower classes also have a zero tolerance .
SEED CLASSES AND TOLERANCES
Flush through (out) system
To guarantee a regular use of healthy seed, after each field generation seed stocks are automatically downgraded to the next class.The classification of a certain seed lot thus depends on the number of generations from pre-basic seed and the quality found during inspections. In the past in seed programmes most emphasis was given to virus diseases. It is now more and more realized that quarantine diseases need more emphasis.