Art and Science of Soybean Maturity Ratings
DuPont Pioneer, Syngenta and others are now doing research on suitable maturity corn and soybeans at company research stations in Manitoba. At one time, DuPont Pioneer’s station was largely dedicated to canola research, but it is now fully multi-crop.
“Our research into double zero and triple zero is much more eff ective there than it was before,” said Schnebly.
Moving west has its own complications with maturities. Although the group rating is largely determined by when the photo period triggers reproduction, it is also influenced by climate. A generally warming climate is expanding expected frost-free days. This has affected the move north, but may also impact other areas to a lesser degree.
“We may see a slight change in ‘fuller’ season maturity recommendations in many areas,” said Tigges. “Regardless of when you plant, the typical soybeans will mature at around the same time. However in northern growing areas, if you used to risk frost the first half of September and now it is the first of October, that allows you to plant a longer season variety or consider planting soybeans as a cash crop where you never did before.”
In the increasing elevations of the West, frost-free days and associated factors come into play. “As we increase in elevation, we go to a shorter season variety, but we are also going to a drier environment,” said Schnebly. “As breeders look ahead, they talk about diversity in germplasm. The question is how fast can we integrate germplasm in a variety while maintaining maturity.”
Expanding geography for planting soybeans and fluctuating weather complicates selection of soybean seed with the right maturity rating.
MOVING RESISTANCE TRAITS
The diversity question comes into play in more traditional maturity zones as well. Even though higher temperatures with climate change won’t influence maturities, it is having an influence on disease. As a result, breeders are working to move resistance to traditionally more southern diseases and pests from determinate, long-season, group five and six varieties north to indeterminate, group 4 and earlier varieties.
In many cases, that is easier than selecting for maturities, thanks to advances in trait marker technology. While markers can verify that soybean cyst nematodes, sudden death syndrome or iron chlorosis traits are present in the new variety, only time spent in a given location identifies the maturity.
“Developing a new variety is a combination of markers and local evaluations,” suggested Schnebly. “Marker technology and the use of tropical nurseries has shortened the variety development program to seven to eight years versus 10 to 15 in the past. Although we’ve made significant progress in identifying genes that affect maturity and other aspects of the soybean crop, the soybean industry is still in the early phase of finding markers for maturity.”
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