Cultivar Maintenance and Seed Certification
Thomas G Chastain
CSS 460/560 Seed Production
Crop Breeding
• Crop breeding is the systematic
improvement of plants to meet
human needs.
• Breeding began with the early
domestication of the wild plant
ancestors of today’s crops. These
improved crop populations are known
as landraces and are endemic to a
particular region.
Sorghum breeding
Crop Breeding
• The breeder must have genetic
variation in order to improve plants.
• Breeders identify new favorable
genetic combinations and
incorporate these traits in the
development of new cultivars.
• The achievements of crop breeding
include:
1. Increased yield
2. Resistance to pests
3. Improvement in quality, i.e.,
taste, color, aesthetic factors
4. Adaptation to mechanical
harvest and other management
practices
Genetic variation in bean seed
size and seed coat markings
Genetics/Biotechnology
Crop Breeding
Seed Production
Crop Production
Consumer
Genetic Delivery System
• Crop breeding is a part of the genetic
delivery system, where favorable
genetic traits found in nature by
breeders or created by a variety of
techniques, are passed through this
system to the consumer.
• Seed production is the means by
which small quantities of seed
containing the desired traits are
multiplied to the large quantities of
seed required for commercial sale of
the trait to the consumer.
What is a Cultivar?
• A cultivar or cultivated variety is a
subdivision of a kind which is
distinct, uniform, and stable.
• A kind is a group of subspecies or
cultivars, collectively known by a
common name.
• Wheat, alfalfa, soybeans, sheep
fescue, and tall fescue are
considered to be kinds.
• Cultivars are the end-products of
the efforts of plant breeding
programs.
• Cultivars may be propagated by
seed or vegetative propagules.
Sheep fescue
Cultivar Evaluation
• Evaluation of cultivars is an
important component of the
crop breeding process.
• Ensures that new cultivars
meet the end-use standards
demanded by the consumer.
Turf grass cultivars in evaluation trial in
Oregon (top) Oregon-grown ryegrass
seed used to over-seed dormant
Bermuda grass field in the 2001 Fiesta
Bowl in Arizona (left).
Features of a Cultivar
• Distinct -- Can be differentiated by
one or more identifiable
morphological, physiological or
other characteristics from all other
cultivars of public knowledge.
• Uniform -- Variation in essential
and distinctive characteristics is
describable.
• Stable -- Cultivar will remain
unchanged to a reasonable degree
in its essential and distinctive
characteristics and in its uniformity
when reproduced or reconstituted
as required for the different
categories of cultivars.
Sunflower
Types of Cultivars
• Need to know the type of cultivar
and breeding history to produce
seed without losing essential
characteristics described by the
plant breeder.
• Line -- Consists of one or more selfor cross-pollinating genotypes and
single line apomicts. Examples are
wheat, soybeans, and Kentucky
bluegrass.
• Clonal -- A vegetatively propagated
(non-seed propagated) cultivar
such as potato. Advancements in
somatic embyrogenesis systems
allow the production of synthetic
Wheat seed field near La Grande
seeds in some species.
(top), potato field (bottom).
Types of Cultivars
• Multiline -- Consists of two or more
near isogenic lines of selfpollinating crops that are similar in
most characteristics, but differ in a
limited number of describable
physiological or morphological
characteristics.
• The lines are grown separately and
are composited to form the
Breeder seed. Examples are wheat
and oats.
Wheat
Types of Cultivars
• Open-pollinated -- Consists of
cross-pollinated plants selected to
a standard which may show some
variation, but can be
differentiated from other
cultivars. Example: ‘Gold Bantam’
sweet corn
From Poehlman and
Sleper, 1995
Types of Cultivars
• F1 Hybrid - Consists of F1
progenies of controlled crosses
between: 2 inbred lines, 2 single
crosses, a single cross and an
inbred line, or two clones.
• Examples include sorghum, corn,
tomato, and cabbage.
Inbred line 1
male-sterile
X
Inbred line 2
male-fertile
F1 hybrid (single cross)
Hybrid sugar beet seed field in the
Willamette Valley.
Types of Cultivars
• F2 Hybrid - Derived from the
progeny of the hybrid F1
generation. Example: tomato.
• Hybrid cultivars cannot be
reproduced from seed of the
hybrid generation.
Inbred line 1
male-sterile
X
Inbred line 2
F1 hybrid (single cross)
F2 hybrid
Tomato
male-fertile
Types of Cultivars
• Synthetic -- Seeds are produced
by interbreeding a population of
inbred lines, clones, or other
populations of cross-pollinating
plants. Pollination is not
controlled in the production of
the synthetic cultivar.
• The components (clones, inbred
lines, etc) of the synthetic are
maintained and the cultivar can
be reconstituted as needed.
• Examples include perennial
ryegrass, tall fescue, orchardgrass
and alfalfa.
Alfalfa
Clones
Polycross Nursery
Progeny Test
Selected Parental Clones
Syn 1 Seed
Syn 2 Seed
Syn 3 Seed
Steps in Synthetic Cultivar
Development and Seed Production
• Advanced generation synthetic cultivar
example. Clonally propagated plants
that have desirable characteristics are
selected and allowed to randomly crosspollinate in a polycross nursery.
• Seed is harvested from the clones and
planted in a progeny test for evaluation.
The best clones are selected as parents
and are permitted to cross pollinate.
Seed harvested from the parental clones
constitutes the cultivar. No more than 3
generations during seed increase.
Clones
First Generation Synthetic Cultivar
Development and Seed Production
Polycross Nursery
Progeny Test
Selected Parental Clones
Syn 1 Seed
Polycross nursery for bentgrass
(top), Stolon bed for clonal
parents of Penncross creeping
bentgrass near Albany (bottom).
Apomixis
• Apomixis is the production of seeds
and vegetative propagules in parts of
the plant normally concerned with the
sexual process, but without the fusion
of gametes. Agamospermy is apomictic
seed production. Kentucky bluegrass
produces seed by agamospermy.
• Main features of apomixis: substitution
for meiosis and fertilization, found in
the flowering parts of plants, occurs
without the fusion of gametes.
• Progeny of apomictic plants are
uniform and identical to the parent
plant. Pollination may or may not be
required in apomixis.
Kentucky bluegrass seed
Changes in Cultivars during Seed Production
• Mutations.
• Late Segregation.
• Out-crossing.
• Early Harvest.
• Mechanical Mixture.
• Genetic Shift - change in makeup
of cross-pollinated cultivars as a
result of environmental selection
pressure. Caused by photoperiod,
winter temperatures, disease, and
competitive ability. Problem in
open-pollinated and synthetic
cultivars when seed is produced
outside area of adaptation.
Mean Freeze Free
Period
Procedure for preventing genetic shift
• Breeder seed produced in the area
of adaptation.
• Limit the number of generations
grown outside the area of
adaptation (3 or less generations).
• Limit the life of the stand (4 to 5
years).
Red clover
For preventing change other than genetic shift
• Same cultivar not recently grown
on same land.
• Remove off-types.
• Observe isolation distances.
• Start seed production with breeder
seed.
• Avoid mechanical mixtures.
Sorghum
Seed Certification
• Purpose of seed certification is to maintain
genetic purity and identity of a cultivar
while increasing the quantity of seed
available.
• Certification is a voluntary program.
• Seed grower agrees to abide by the
standards set forth by certification agency.
Both public and proprietary cultivars can be
certified.
• Only 10% of US seed crops are certified.
Most of the non-certified seed is comprised
of corn, soybeans, and small grain cereals.
• Between 50 and 60% of Pacific Northwest
seed crop acreage is certified. This seed is
largely destined for foreign and domestic
export markets.
Seed Certification Classes
• Breeder Seed. The production of
breeder seed is supervised by the
plant breeder.
• Foundation Seed. Foundation seed
is produced from breeder seed by a
foundation seed organization.
• Registered Seed. The second
generation from breeder seed.
Registered seed is sometimes
eliminated under the limited
generation system.
• Certified Seed. Certified seed is used
as planting stock for general crop
production.
Breeder Seed
Foundation Seed
Registered Seed
Certified Seed
Seed Certification Procedures
• Application. Only eligible cultivars
are considered.
• Seed Source Verified.
• Field History Established.
• Isolation Distances Must be Met.
• Crop Inspection at Seedling Stage.
• Mature Seed Crop Inspected.
• Seed Cleaned at Approved
Warehouse.
• Seed is Sampled and Tested for
Purity, Germination, and Noxious
Weeds.
• Seed is Tagged.
Aerial field inspection by helicopter
(OSU Seed Certification Photo)