Stock seed, also known as breeder's seed, is the highest quality seed maintained by the breeder to ensure genetic purity. There are different classes of certified seed including breeder, foundation, registered, and certified seed. Maintaining genetic purity of stock seed is important and involves minimizing contamination and strictly rogueing off-types before pollination. Producing stock seed infrequently helps maintain genetic purity over time by reducing genetic drift. Proper storage methods like cool, dry conditions also preserve genetic integrity.

1. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
www.seedalliance.org
Stock Seed
Laurie McKenzie
PNW Research and Education Associate
Organic Seed Alliance

2. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
What is Stock Seed?
• Also referred to as Breeders’ Seed
• Generally maintained by the breeder
• Highest quality seed to ensure genetic
purity

3. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Classes of Seed
• Breeder Seed – source of all classes of certified seed
• Foundation Seed – progeny of Breeder or Foundation seed
produced under the control of the originator
• Registered Seed – progeny of Breeder or Foundation seed
produced according to policies and procedures of a regulating body to
maintain genetic purity and identity of a variety. Some crops and varieties
have no Registered class.
• Certified Seed – progeny of Breeder, Foundation, or Registered seed
produced according to policies and procedures of a regulating body to
maintain genetic purity and identity of a variety.

4. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
U.S. Federal Seed Act
The purpose of the Act, which has state counterparts
that may require more disclosure or standards, is for
everyone to know what is exactly in the bag. The Act
generally applies to any vegetable or agricultural seeds,
including lawn and forage seed, that are shipped in
interstate commerce or will eventually be shipped in
interstate commerce.

5. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Bag Labels must include:
• Name and/or Variety of Seed (% if mixed)
• Lot Number
• Origin
• % Weed Seed
• % Inert Matter
• Germination Rate (variable depending on
crop) – must be done within last 5 months
• % Hard Seed

6. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
In General,
Genetic Purity of the seed planted must equal or
exceed that of the final product.
Genetic purity generally decreases with each
subsequent generation of propagation

7. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Seed Genetic Purity Standards are set by state
seed laws and seed certification agencies to
ensure buyers receive quality seed.
Genetic purity tolerance levels are determined
by:
• Biology of the species (self- or cross-
pollinated)
• Variety type (open pollinated or hybrid)
• Market-driven standards

8. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Early Generations such as Breeder and
Foundation seed have stricter standards for
genetic purity.
For Example in California:
Max off-types in Foundation Seed = 0-0.2%
Max off-types in Certified Seed = 0.1 – 2%
* in one pound of Certified seed this would
mean (same crop, different variety):
- 1 cotton or wheat seed
- 2 watermelon seeds
- 4 rice seeds
- 6 sunflower seeds

9. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Sec. 201.31 Germination standards for vegetable seeds in
interstate commerce. The following germination standards for
vegetable seeds in interstate commerce, which shall be construed to
include hard seed, are determined and established under section
403(c) of the act. Type Germ %
Artichoke 60
Asparagus 70
Bean, Asparagus 75
Bean, Fava 75
Bean, Garden 70
Bean, Lima 70
Bean, Runner 75
Beet 65
Broccoli 75
Brussels Sprouts 70
Burdock, Great 60
Cabbage 75
Cabbage, Chinese 75
Cabbage, Tronchuda 70
Cardoon 60
Carrot 55
Cauliflower 75
Celeriac 55
Celery 55
Chard, Swiss 65

10. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Self & Cross-Pollinating
Species Spectrum
SELFERS CROSSERS
Peas Lettuce Tomato Pepper Squash Umbels Corn Brassicas
Selfers require
minimum isolation
Crossers require
much greater isolation
Save from
few plants
Save from
many plants

11. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
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Roguing
• Moving forward to keep from moving backward

12. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Selection
Maximizing Selection
• Uniform field conditions
• Consistent and uniform treatment
• Large population size
• Select before pollination
• Grid selection

13. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Selection
Natural Selection favors
reproductive traits
Artificial selection required
for quality

14. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Genetic Drift
Genetic drift is the random change in the frequency
of genes in the population as it reproduces. Even in
the absence of selection, the plants that grow from
one generation to the next may have a slightly
different percentage of genes just due to chance.
This can result in genetic changes in your variety
over time. This is one reason breeder / stock and
foundation seed are produced infrequently.

15. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Maintaining Genetic Purity in Stock Seed
Minimize and be aware of contamination from:
• Prior crops grown in the field
• Pollen transfer from nearby fields
• Mixtures during harvesting and handling
• Strict rouging of off-types
• Before pollination

16. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Stock Seed Can Be Produced:
Frequently – allows the variety to
evolve and adapt
Infrequently – best for maintaining
genetic purity and minimizing change

17. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Seed Storage
~ Cool, dry, and dark.
~ Minimum fluctuation of storage conditions.
~ Heat and humidity together should stay under 100.
~ Airtight containers with desiccant, or breathable cotton muslin bags.
~ Protection from pests.

18. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Underground Storage

19. Advancing the ethical development and stewardship
of the genetic resources of agricultural seed
Considerations in Stock Seed
Production:
• What is your goal?
• What is your storage capacity?
• Commercial contract stipulations
• How much do you want the variety to stay the same
over time?
• Will you certify or register the seed?