Everyone talks about the importance of genetic diversity, but a few of us still remember why. Forty years ago a new race of southern corn leaf blight decimated much of the nation’s corn crop. It happened because 80% of the U.S. corn acres were developed using Texas male sterile cytoplasm or “T cytoplasm.” Widespread use of this cytoplasm created a uniformly susceptible crop.
The seed industry corrected the cytoplasm situation, but today it remains just as important for growers to maximize yields while minimizing risk by planting a lineup of unique hybrids across a range of maturities.
Chad Geater, breeding project hybrid lead for Syngenta Seeds, says diseases like Goss’s Wilt and Diplodia Ear Rot are modern day lessons of why growers should be careful to select hybrids with diverse genetics.
“Hybrids respond differently to different environments,” says Geater. “Narrow genetic diversity compromises the ability of germplasm to respond to a changing environment.”
Eric Boersma, corn portfolio manager for Syngenta Seeds, sees two components in the diversity discussion. “It’s important for growers to consider the depth of genetic diversity within the seed company portfolio and it’s important to take advantage of that diversity.
“That’s why we often recommend a package of hybrids,” says Boersma. Too often, he sees growers attempting to select for a characteristic—ability to withstand high populations, for example—choosing similar hybrids to reach their goal. “We’re also noticing that as growers take on more land they try to plant more of the same to make their operation more efficient,” Boersma adds. “In the process, they could also be limiting their genetic diversity.”
Roger Elmore, Iowa State University agronomist, says simply planting different brands of seed corn isn’t the same as genetic diversity either. “Check your seed tags,” says Elmore. “Variety number and the brand number are not the same.”
The Federal Seed Act stipulates that no commercial corn hybrid may be sold under two or more variety names. This seed law also requires that seed corn tags or bags identify the pedigree of the hybrid. Therefore, growers should carefully check the seed corn "bag tags" to avoid planting hybrids that contain the same genetics. Seed providers should be willing to help you locate this information, as well as provide more details on the genetic diversity available within their product offerings.
“If you notice the hybrid has the same maturity ratings, disease ratings and identical traits, there’s a good chance they are closely related,” Elmore adds.
In season, Geater urges growers to get to the field to compare hybrids in preparation for 2012. “If you can’t tell where one hybrid starts and the other stops, there’s a good chance they are related,” Geater says.
“Tassels are one of the main visual clues that hybrids are from different genetic backgrounds,” he adds. “You’ll be surprised at the different colors and shapes of tassels.” Leaf shape and color and size and shape of ears provide other clues of genetic diversity.