Hybrid seed corn is so common today we hardly think about it. In fact, more than 95 percent of corn planted today is hybrid corn. Thanks to hybrid seed, today’s farmers are able to produce 20 percent more corn on 25 percent fewer acres than they did a century ago.
It was a geneticist from New York, G.H. Shull, who began experimenting on inheritance in the early 1900s. His experiments were the basis for hybrid corn and included observations on the reduction in vigor on inbreeding and the restoration of vigor on crossing. There were other experiments taking place at the time, as well, and the general consensus was that hybrid corn could not be achieved because of the poor vigor of inbred parents.
Open-pollinated varieties are maintained through mass selection. Windborne pollen impacts fertilization with no control of male parentage. Inbred lines are derived from a mix of inbreeding and selection. Inbreeding transfers pollen from an individual plant to silks of the same plant. When this process is repeated over several generations, the strain becomes stable.
In order to maintain only the superior hybrids, selection is practiced in every generation. Cross-breeding involves the crossing of selected parents. Single crosses are produced by two inbred lines, double crosses by crossing two different single crosses.
In 1918, the Connecticut Agriculture Experiment Station double crossed hybrids from four inbred parents. This helped to lessen the impact of poor vigor of inbred parents. Released in 1921, this male hybrid corn was the first to be produced commercially.
The early 1920s saw many inbreeding and hybridization programs. Since basic genetic theory was inadequate at the time, new procedures had to be developed. Hundreds of inbred lines were isolated and evaluated in thousands of crosses.
When corn hybrids initially became commercially available, farmers were still reluctant to adopt them. That began to change as demonstrations were held and field observations took place. By the mid-1930s, demand exceeded production and the hybrid seed industry was up and running. Since that time it has showed no signs of slowing.
While it is true that hybrids have allowed for an increase in corn production, they have done much more. Hybrids allow for efficient use of applied fertilizer. They also allow for resistance to a variety of insects and diseases, leading to higher quality corn. Finally, the uniformity in maturity and lodging resistance in hybrid corn have made large-scale mechanization possible.