Stacks of Traits

December 8, 2010 05:32 AM

New and improved may be fine for breakfast cereal, but Mike Bland tries to look beyond the bells and whistles when buying seed corn. “Yield is still my main priority,” says the Bethany, Ill., farmer.

“The number of trait combinations and brands on the market today can make hybrid selection confusing,” Bland says. “I study a lot of independent yield trials to sort through it. I like the added protection that traits offer, but I want them in addition to, not at the expense of, yield and profit.”

The trend toward stacking biotech traits to package herbicide tolerance and insect protection continues in the product pipelines of biotech providers.

In 2010, the corn market became almost a pure genetically modified (GM) market. USDA’s Economic Research Service reports that this past year, 86% of corn acreage was planted to GM varieties and half of that was devoted to “stacked varieties.”

The list of shopping options grows in 2011 with an all-new multi-pest insect trait, a new blended refuge concept and the first hybrids bred to weather water stress hitting the market.

Choice is not the issue. Choosing is, and Farm Journal Field Agronomist Ken Ferrie says the 2010 growing season served up some reminders that corn traits are not foolproof, nor are traits guarantees of yield.

“In the past, the traits that helped protect roots were especially helpful when we got into drought summer situations,” Ferrie says. “This past year, the problem was not so much drought as sustained, elevated nighttime temperatures. As a result, the plant spent a lot of energy respiring, rather than devoting that energy to the ear.”

Producers eagerly adopted European corn borer (ECB)–resistant transgenic hybrids when they debuted in 1996. Bacillus thuringiensis (Bt)–enhanced crops also reduced pesticide use.

Research conducted by several Midwestern universities shows that suppression of ECB has saved $3.2 billion for corn growers in Illinois, Minnesota and Wisconsin during the past 14 years.

Comparable estimates for Iowa and Nebraska total $3.6 billion. In Illinois, ECB densities have reached historic lows and have many questioning if it should still be considered a pest.

Ferrie maintains that GM traits are as crucial today as ever, especially as secondary pests come into play. “Growers fighting corn earworm and western bean cutworm benefit from new technology because those pests are hard to monitor and spray for,” he says.

Iowa State University agronomist Roger Elmore reminds growers that no two years are alike and the chance of choosing a high-yielding hybrid significantly increases if it has performed well across multiple sites and/or years.

“What doesn’t change is that transgenic traits are designed to protect yield, not increase it,” Elmore says.

Trait tools. Single-trait hybrids exist, but stacks dominate the marketplace. Choosing is complicated because not only can the number of traits stacked into individual transgenic hybrids differ, but there are differences in which pests they control and how.

While there are more than 100 variations of Bt insect resistance, there are two broad resistance categories. One category of Bt protects corn from belowground rootworms. The other provides resistance to aboveground, moth-type insects, such as ECB.

When it comes to weed control, there are only two herbicide-tolerant traits available for 2011: Roundup Ready, which allows corn to tolerate glyphosate, and Bayer CropScience’s LibertyLink trait, which tolerates Ignite (glufosinate).

This past spring, SmartStax, the eight-way stack from Monsanto Company and Dow AgroSciences, made it to fields. The technology struggled in some areas of the central Corn Belt in terms of yield, but it showed more strength in northern regions and in areas that experienced significant insect pressure.

The insect combination of SmartStax protects against aboveground insects, such as ECB and corn earworm, fall armyworm, western bean cutworm and black cutworm. Herculex and YieldGard traits tag-team to protect against corn rootworm. SmartStax hybrids contain Roundup Ready and LibertyLink herbicide technologies, offering the flexibility of two herbicide modes of action. Expect to see the SmartStax and Genuity SmartStax trait package offered in a wider variety of hybrids in 2011.

Genuity VT Triple Pro and Genuity VT Double Pro also launched in 2010. You give up the option of using Ignite with these stacks. VT Triple Pro has both aboveground and belowground protection while Double Pro is aboveground only (no rootworm). Both provide more comprehensive corn earworm and fall armyworm control than YieldGard hybrids, but not the western bean cutworm or black cutworm protection of SmartStax.

All new for the coming season is Syngenta’s Agrisure Viptera (Vip3A) trait, a class of insecticidal vegetative proteins that have not previously been used in Bt corn hybrids. Vip3A is the corn industry’s first non-Cry (non-crystalline) insect control protein. That’s important because it provides a different mode of action that reduces the chance of insects becoming resistant.

The Vip3A trait will be combined with Agrisure GT 3000 to form the Agrisure 3111 trait stack. The three Bt proteins present in Agrisure 3111 offer above- and belowground insect control of 14 different pests. The Agrisure 3110 trait stack is another option for growers who want the above-ground benefits of a stack that includes Vip3A but have no need for rootworm protection or who are looking for refuge options. Both of the Agrisure Viptera trait stacks offer the dual
herbicide options of spraying glufosinate and glyphosate.

Refuge reductions. If there is one thing that turns Bland from focusing purely on yield, it is the potential of refuge elimination. “It would be mighty convenient,” he admits.

He won’t see that happen this year, however. Trait technology providers expect to have integrated refuge available in 2012.

For 2011, the bulk of trait technologies still follow the previous requirement for Bt corn in the Midwest: a 20% structured refuge for ECB and corn rootworm. SmartStax usage allows a 5% refuge. VT Double Pro drops to 5% in the Midwest and 20% in most cotton regions. Southern growers should check with their seed representative to make sure they qualify.

What is available for the first time next spring is Pioneer Hi-Bred’s Optimum AcreMax 1, which offers an in-the-bag corn rootworm solution. The system is 90% of a Pioneer brand hybrid with Herculex XTRA insect protection and 10% of a Pioneer brand hybrid with the Herculex I trait, which serves as the integrated corn rootworm refuge. A corn borer refuge is still required, but the refuge can be placed up to ½ mile away.

Bill Belzer, Pioneer senior corn marketing manager, explains that by providing the corn rootworm refuge in the bag, growers would no longer be faced with the challenge of placing traditional in-field or adjacent refuge for triple-stack products.

“It also helps growers with rootworm pressure to maximize their yields by placing integrated in-plant rootworm protection across all of their acres,” Belzer says. “Placing the corn rootworm refuge in the bag assures the refuge gets placed in the right place, in the right size, at the right time to extend the durability of the Herculex family of traits,” he adds.

Plants that sip. Hybrids that are more efficient in using water resources will find their way to farmers’ fields this spring as well. Pioneer is on track to launch its Drought 1–tolerant corn in the western Corn Belt.

Jeff Schussler, senior research manager at Pioneer, explains that the hybrids use native genes that fight off stress. Researchers have selected for characteristics such as deeper roots, different leaf-rolling patterns and better silking to bring hybrids of more stable yield in limited-moisture situations.

Syngenta is also on track for a 2011 launch of water-optimized hybrids. Tracy Mader, head of product marketing for Syngenta corn and soybeans, doesn’t call the new technology “drought tolerance.” Rather, “it’s a more comprehensive answer to the year-to-year variations in heat and water stress,” he says.

Hybrids in the Agrisure Artesian line are the result of discovering and integrating specific traits capable of enhancing yield on dryland and limited-irrigation acres.

“We’re never going to turn Nevada into Illinois,” Mader says. “It’s one thing to have a product that manages moisture, but it also has to be put into genetics that perform.”

Multiple-Trait Rules of the Road

When stacking multiple traits into hybrids, Roger Elmore of Iowa State University offers the following pluses and minuses.


  • Reduction of acreage planted to refuge hybrids are allowed with some technologies.
  • If reduced yields occur with the refuge, planting fewer acres to the refuge will result in more yield.
  • Stacking multiple traits for aboveground insects will in some cases increase the range of insects that are controlled.
  • Adding additional traits for the same pest may increase the durability of the traits and delay the development of pest resistance.


Possible disadvantages

  • Reducing refuge acres might not increase yields. Refuge hybrids can produce comparable yields if either no insect pressure occurs or insecticides effectively control insects.
  • Increasing the number of traits protecting against the same pests will not necessarily improve insect pest control or yield.
  • Adding two traits to control the same pest may increase durability of the traits, but this is true only if each trait acts in a unique manner to control the insect pest.
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