DuPont Pioneer researchers are working to help growers understand the risks of planting in cold, wet seedbeds and mitigate those challenges with corn hybrids that tolerate less-than-ideal soil conditions. Many Pioneer? brand hybrids feature strong stress emergence scores, which indicate a relative ability to emerge in cooler conditions, tolerate early-season challenges and give growers the opportunity to produce high yields.
"Stress emergence isn't just a trait for northern growers," notes Imad Saab, senior DuPont biotech business affairs manager. Saab has been on the forefront of stress emergence work at Pioneer for more than a decade. "This is a valuable trait for growers everywhere who are planting corn earlier or into cool, damp soils. With the rise in no-till or minimal-tillage systems, more corn is being planted into inhospitable soils."
Growers in northern states are aware of cold stress issues. Saab reports many questions about stress emergence come from states farther south.
"Growers in the south can start planting in March or possibly late February if conditions allow it," Saab says. "In Kentucky, for example, early-planted corn can experience cold, wet conditions, particularly in no-till environments. Soils can remain cold and damp for weeks after planting." These conditions can significantly reduce the number of emerged plants.
"We're leveraging the genetic diversity of corn and cutting-edge molecular breeding tools to improve stress tolerance in hybrids," Saab says. "We identify germplasm that tolerates cold and water logging better, and we use this information to enrich our corn lineup with hybrids that excel in early-season performance."
Because corn historically is a warm-weather crop, finding strong cold tolerance in germplasm collections isn't easy. It takes diligent research and the ability to evaluate massive numbers of genetic lines in combination with molecular breeding tools.
"We've tackled the problem with good, old-fashioned field selection in the past," Saab says. "In recent years, we've added predictive lab testing capabilities along with molecular markers to enrich our pipeline for these traits. Using all three methods in combination gives us a high level of confidence that we're identifying and advancing the best germplasm to meet these challenges."
Growing the plant out in field settings allows Pioneer researchers to place them in areas subject to very cold springtime conditions including snow. The growing environment essentially tells them which hybrids are performing well.
"Field testing allows us to monitor other traits as well," Saab says. "We continue observations throughout the growing season, so we get lots of data we couldn't collect in lab testing alone."
The lab does offer some advantages, however. Pioneer is using unique lab tests that are carefully calibrated with data from field trials. This means the lab test results correlate very highly with field measures of plant performance under stress.
"Lab testing has become one of the backbones of our yearly hybrid selection process," Saab says. "We can test higher numbers of lines, test them year round and make sure commercial lines will perform as predicted."
Molecular markers provide another method of identifying genes that provide cold tolerance and stress emergence benefits. Pioneer is using whole-genome prediction, which targets many markers at once, developing profiles of lines with the more advantageous genes for a particular trait.
"We use our extensive set of molecular markers and bioinformatics tools to predict how these lines will perform in the field," Saab says.
Pioneer combines the results of lab and molecular marker tests and advances the best candidates to field testing.
"Using all three methods provides strong validation that the traits we incorporate will be expressed as we expect," Saab says. The goal is to give growers tools to make better management decisions.
"We want to provide every grower a menu of products they can choose to meet their own local needs," Saab says. "One grower may require strong stress emergence traits. Another may emphasize other traits." If the second grower knows a hybrid has a lower stress emergence score, he or she can use other management approaches to mitigate the risks of early-season stress. For instance, this operation may plant later or plant this hybrid only in dry, well-drained soils.
