Don't miss Corn Breeding 101!

Inbred lines are the two parents that make up a hybrid. Plant breeders first select possible inbred lines form thousands upon thousands of candidates in nurseries. Then the next task is to find to inbred lines that best match with each other.

Inbreds are 'staff of life': Note that the inbreds in this DeKalb breeding nursery, to the far right, are already all brown, while hybrid plots, to the left, are green. Crossing inbreds to makes hybrids improves many qualities, including stay-green power.

Dave Nanda, a plant breeder and now consultant for Seed Consultants, Inc., says that the process of finding an inbred line and then crossing it with another inbred line to form a hybrid that is better than other things on the market already can take up to 10 years from the time the first inbred is found until the seed arrives at your farm. Modern techniques in breeding are shaving years off that cycle, but it's still a long process.

There are lines that make better males, which provide the pollen but are never harvested for seed. And there are lines that make better females, which receive pollen from the males and are harvested for the seed. The seed from these female rows is hybrid corn, Nanda says. You plant it once and shoot for top yield. If you try to plant it again, it will begin to revert back into parent lines, and you won't have uniform plant types. You will have a rogue's gallery of plants, some being very good, but some perhaps not procuring an ear at all.

Through the years plant breeders have tried various concepts, including double crossing, which involves three or four parent lines. However, several decades ago most breeders concluded that the most hybrid vigor with the most yield kick came from the first cross of the right tow inbred lines with one another.

When you pour seed into your planter today, it's likely a single cross made by growing two inbred lines in the same seed field. If you visit the seed field, neither inbred would impress you, Nanda says. But the combination of genetics packed into offspring from the cross, coupled with cultural techniques, will carry you to higher average yields in the future.