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Competency Area 4: Seeding Factors

PO 17. Know the factors that influence corn hybrid selection in the Northeast.

What is a Hybrid?
A Hybrid is the first generation offspring of a cross between individuals differing in one or more genes. Hybrids often have better vigor (yield, size, maturity) than their parents.

Types of hybrids: click on images to enlarge

single cross hybrid

Single cross hybrid – progeny of a cross between 2 parents

double cross hybrid

Double cross hybrid – progeny of a cross between two single crosses (has 4 parents)

three way cross hybrid

Three way cross hybrid – progeny of a cross between a single cross and another parent (has 3 parents)

 

Varietal Hybrid - progeny of a cross between two varieties

Corn open-pollinated varieties (OPVs) are genetically variable because they are a mix of many different hybrids. Farmers can save seed of an OPV because the same mix of genes generally will be there from year to year. The same OPV can change gradually from selection. Natural selection occurs due to the environment where the OPV is grown. A farmer can influence selection by picking the best ears from the best plants. Thus, seed of a named OPV from different seed producers may be slightly different.

 

Corn hybrids are usually seed produced by crossing inbred parents. Inbreds are a result of continued pollination of a plant, by itself.  Inbreds are genetically uniform or true breeding. A field of an inbred that receives only its own pollen will produce seed that is genetically the same as what was planted. Inbreds are generally short, have small ears and seeds (lots of rounds).

Most corn hybrids today are single crosses of two inbred parents. Farmers should not save seed from a hybrid planting because the resulting plants will be extremely variable and will not perform as well as the original hybrid seed.

For Grain Production
The most important trait is the right maturity.  Other important traits include high grain yield, strong stalk and good roots, and a high test weight.

For Silage Production
The most important trait for corn silage is the right maturity (mid milk line for silage).  Other important qualities are high tonnage (grain+stalk+leaves) and high digestibility (highly affected by management factors, including hybrid selection, plant densities, and harvest timing as well as silo management). Other characteristics depend on grower’s interest and needs!