Genetic diversity involves planting a portfolio of hybrids from different genetic families to help reduce risk. This diverse selection can help increase your ability to grow consistent-yielding corn every year.
Ten corn genetic families are used in the development of hybrids: Northern, Southern, Eastern, Eastern 2, Western, Tropical, Early Health, Late Health, High Yield and Flint.
Developed years ago by farmers using the earliest method of plant breeding called mass selection, these genetic families originated with the first open-pollinated corn varieties. Each year, farmers saved the best ears for seed to plant next year’s crop. This enabled genetics best suited for particular localities to be selected. For example, farmers in Ohio, Maryland and Pennsylvania selected genetics tolerating the saturated soils and disease pressure found in the high-rainfall eastern Corn Belt. To reduce risk in this high-disease environment, corn plants required thick rinds making strong stalks, which provided standability in severe stalk-rot environments. Local farmers, selecting for these traits, developed the Eastern Genetic Family.
Likewise, farmers selected the Northern Genetic Family for cool tolerance and the Southern Genetic Family for heat tolerance. The Western Genetic Family tolerates the drought conditions in the drier areas of Kansas, Nebraska and South Dakota. Favorable soils and weather in Iowa promoted the selection for maximum yield called High Yield Genetic Family.
The Early Health and Late Health Genetic Families added disease resistance, which allowed hybrids to stay green and alive in the fall, facilitating standability. Flint genetics were used to add test weight and cool tolerance. The Tropical Genetic Family added heat and disease tolerance, which is necessary for survival in the hot and humid Deep South, where winter infrequently interrupts disease cycles.
Further strengths and weaknesses of each genetic family are outlined in the Genetic Families <link to 2.3.3.18> section. Other genetic families not falling into these 10 most frequently used categories are called “Unrelated,” since they are unrelated to the 10 main families.
The “save-the-best-ear” selection method of early corn farmers was only partially effective because corn is cross-pollinated. Seed saved from corn plants having the best ear received only half its genetics from that plant. The other half came from pollen contributed by unidentified neighboring plants. With the development of the hybridization system, control of both the female seed-bearing plant and the male pollen-source plant enables plant breeders to combine several genetic families into one hybrid, merging the strengths of each genetic family into one plant.
In addition, hybridization provides the opportunity for plant breeders to correct weaknesses. For example, the maximum genetic yield potential of the High Yield Family can be combined with the disease tolerance and stalk quality genetics of the Eastern Family, creating high-yielding hybrids with disease resistance and stalk quality. Just like the High Yield Family crossed with the Northern Family develops high-yielding hybrids tolerating cool weather.
Plant breeders frequently combine two genetic families into one parent line. Therefore, these two parents produce a hybrid that is a combination of more than two genetic families, influencing characteristics from all the genetic families used. In addition, a parent line derived from two genetic families can have a varying percentage of genes from each family. The parent line could have a 50 percent contribution from each genetic family. Or, it may have 10 percent from one genetic family and 90 percent from the other, depending on the breeding procedure.
Large, consistent ears at high populations.
Genetic diversity increases the probability of achieving consistent corn yields. Planting only one genetic type risks the entire crop if growing conditions expose a weakness. In addition, knowing the genetic type enables making the right management and placement decisions. For example, Eastern and Northern types can be planted on poorly drained fields, but Western hybrids cannot. Southern types, containing high-yield genetics, are responsive to aggressive nitrogen rates. Northern hybrids, with genes coding for enzyme systems promoting efficient grain fill during typical cool northern growing seasons, are recommended for cool, wet localities.
When planting Bt corn and selecting conventional corn hybrids for refuge acres, Western-type genetics with high native tolerance to corn borer are preferred. Conversely, Western hybrids are the least responsive to Bt technology.
Southern hybrids tolerate sand best with their large ear size and strong ear flex, allowing for reduced plant population as a hedge against drought. Eastern types handle clay and saturated soils best because they have deep penetrating roots that can grow through tight, sticky soil. When using corn rootworm seed to reduce root lodging risk, a conventional hybrid with the strong-rooted High Yield Genetic Family makes the best refuge hybrid. Knowing the hybrid’s genetic type helps you determine which hybrids will work and if their genetic diversity will help reduce risk.
Your CROPLAN GENETICS® seed local agronomist has the resources and expertise to help you make crop management decisions that push performance beyond the expected.