Just as insect-resistant and herbicide-tolerant seed traits helped to increase crop yields, “stress traits,” the next step in the evolution of trait technology, could provide the next big boost to crop productivity. Researchers offer some exciting possibilities — seeds that can tolerate intermittent dry spells or seeds that can perform well with reduced inputs.
“The next generation of seed traits shows tremendous promise for producers,” says Nate Miller, global project leader, corn traits, Dow AgroSciences . “But we have to temper our enthusiasm with the realization that these new stress traits are very complex and can be specific to geography, water availability, soil type and sunlight. And there's also the interaction between various plant processes that can ultimately impact the effectiveness of the underlying trait.”
These traits are complex because various genes interact to affect the plant's productivity. Is a corn plant's ability to tolerate dry periods a direct result of the health of the roots, its tolerance to early season disease pressure, its leaf structure that captures more sunlight, or all of the above?
“Drought is a complex trait and one that is tied directly to corn yield, which in itself has many contributing factors,” says Jeff Schussler, Pioneer senior research manager. “Our research focuses on aspects such as improving root systems or increasing the plant's ability for silks to emerge during drought stress. We have to modify the corn plant's natural conservative tendencies and instead produce more grain per inch of water.”
The first bioengineered crop traits — insect resistance and herbicide tolerance — were, in general, traits that reduced the amount of stress that a plant faces. And these traits were specific: Kill a pest or a weed and the plant has a better opportunity to reach its genetic potential.
As seed companies gain more knowledge about the current traits, they're also finding that they can offer additional benefits. Bruce Battles, Syngenta agronomy marketing manager, says the company's Agrisure 3000 GT hybrids have proven their performance in areas with high rootworm pressure. “But what we're learning more and more is that as we move the traits outside of areas with not as much rootworm pressure, we are still seeing subtle yield increases,” he says.
The next generation of traits includes those that deal with nutrient and water utilization characteristics.
“The nitrogen-use  traits in the pipeline look good,” says Fred Below, professor of plant physiology at the University of Illinois . “In general, those traits have shown that producers can get the same corn yield with 30% less nitrogen.”
However, a reduction in the need for nitrogen can take on many facets. “Nitrogen use can come into play if wet weather has reduced the amount of available nitrogen in the soil, which could mean more uniformity across a field, ultimately increasing overall yield,” he says.
In general, corn producers have not increased the amount of nitrogen applied since the early 1980s. “And yet yields have doubled,” says Roger Elmore, professor of agronomy at Iowa State University. “Now that could be because we were applying too much nitrogen to start with, but we also have to look at how breeding for yield has helped select the genetics that can do more with less nitrogen.”
So do we have stress traits already in the pipeline? Possibly. “Hybrids are far superior today than they were just a few years ago,” Below says. “And better hybrids handle stresses better, like higher populations, cold and drought.”
Evidence of the effectiveness of herbicide tolerance is easy to see — a clean field and dead weeds. But how do you see a slight increase in kernel fill because the plant better used available nitrogen? Truth is, you can't until the crop is in the bin. “That's the way high yields always work; you have a lot of little things working for you,” Below says.
Measuring the new traits will be imperative in proving their worth on the farm. “The next generation of traits will need to have a proven and demonstrable yield impact,” Miller says. “That is a clear hurdle that we will have to cross in the value proposition model.”
In general, that's a consistent 6 to 10% increase over base level yields. “A 4% yield advantage is outstanding, but it is very difficult to prove statistically,” Below says.
Herein lies another difficult task — assessing value and pricing the trait for the end user. “Even a trait that brings a 10% yield increase, but only three out of 10 years, will have a different value proposition than the same trait that offers another producer a 10% yield bump six out of 10 years,” Miller says.
“I doubt there will be any one-size-fits-all solution,” Miller continues. “There likely will be various pricing structures based on the area of the country, conditions, soil type and cropping history.”
Companies are looking at different ways to create the next generation of traits. Syngenta, for example, is looking at water-management traits in both genetically modified and native genes. “We're exploring our library of genetics, pulling out genes that we can mix and match to improve stress tolerance,” Battles says.
BASF Plant Science and Monsanto  announced earlier this year the discovery of a naturally occurring gene that will be used in drought-tolerant corn that could reach the market as early as 2012, pending appropriate regulatory approvals.
And Pioneer plans to introduce its first drought-tolerant corn hybrids as early as 2010, pending product performance in on-farm drought-stressed trials.
Over time, plant breeders have improved the ability of crops to handle various stresses. “That's the nature of the breeding process,” Elmore says. “And we have hybrids that are more stable in cold and more effective against early season diseases. But there's not just one thing we can point to that gives these hybrids the edge. It's an interactive process.”