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Hybridity and varietal purity tests
Hybrid seed is seed produced by cross-pollinating plants
in a controlled environment. Hybrids are bred to improve
the characteristics of the resulting plants, such as
better
yield, greater uniformity, improved vigor,
color,
disease resistance, and so forth.
Today,
hybrid seed is predominant in agriculture and home
gardening, and is one of the main contributing factors
to the dramatic rise in agricultural output during the
last half of the 20th century.
In the U.S., the
commercial market was launched in the 1920s, with the
first hybrid
maize.
Hybrid seed cannot be saved for
replanting without losing the benefits of the original
variety as these traits randomly segregate among the
saved seed, not reliably producing true copies of the
original variety.
New seed must therefore be produced
for each planting.
As genetic purity is a function of seed production, each
hybrid seed lot must be tested
for parentage and purity.
To achieve this, hundreds of
seeds from each seed lot are planted and observed for
uniformity in field tests.
Protein and DNA molecular
marker analyses are also widely used for hybrid purity
testing.
Protein analysis is often prefered because it is less
expensive, but DNA tests are becoming increasingly
affordable.
Similar tests are applied to open-pollinated
and synthetic varieties to assure varietal purity.
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