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Genetic Purity
Genetic purity refers to the percentage of contamination
by seeds or genetic material of other varieties or
species.
The genetic purity of any commercial
agricultural product propagated by seed begins with the
purity of the seed planted.
In general, the genetic
purity of the seed planted must equal or exceed the
final product purity standard required, as purity
generally decreases with each subsequent generation of
propagation.
It is virtually impossible to assure that no off-type
plants or pollen is present in the seed production field
and that all handling and conveyance equipment and
storage facilities are completely free of contamination.
As a result, commercial planting seed is seldom 100%
pure. In practice, practical seed genetic purity
standards have been established by state seed laws and
by seed certification agencies to ensure that the
purchaser receives seed that is within certain purity
tolerances.
These tolerances are established based on
the biology of the species (i.e., self- or
cross-pollinated), the type of variety (i.e.,
open-pollinated, hybrid, synthetic), and market-driven
standards for final product quality.
Earlier generations
of seed (e.g., foundation or registered seed) have
stricter standards in order to be able to meet the
certified seed purity criteria.
The main sources of
contamination of a seed crop are the prior crop grown in
a field, transfer of pollen from a nearby field, and
mixtures during harvesting and handling.
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