Chuck Cunningham held a stalk of Reid's yellow dent corn from 1867 in one hand and a stalk of one of DuPont Pioneer's newest hybrids in the other. Then the Pioneer plant breeder explained some of the advances in yield potential related in just the change of plant structure over the years. The historic corn was open pollinated, compared to the hybrids of today.
First, the old corn had a very large tassel compared to the small tassel on the modern hybrids. "Large tassels take up a lot of energy to make, and aren't necessary," he says. Today's hybrids provide plenty of pollen, at least in normal years, to pollinate plants. It lets the plant devote that energy that would go into making the tassel into something else, and ultimately into more yield."
Another obvious difference was in leaf shape and design. The older plant from 1867 had long, floppy leaves. When planted close enough together, leaves would flop into one another. Today's hybrid used as the example had upright leaves.
"You saw corn with floppy leaves all the way into the 1960s," he says. "Then the higher yielding hybrids tended to have more upright leaves after that."
Often some of the changes aren't because plant breeders set out to select for them, he says. Some of them happen just because the breeders are selecting what is yielding the most. Over time the highest-yielding material tends to have a definite set of characteristics.
Another change that isn't visible by looking is the time between when the plant tassel and when the shoots and silks come out. It was common for tassels to shed pollen before shoots and silks emerged on older corn genetics, he says. One thing breeders have worked toward is narrowing that window. In some hybrids, the silk may even emerge before the tassel sheds pollen.
The idea is for both to happen at about the same time, he says. Unfortunately, the weather interfered with that process in many cases this summer, causing pollination problems.