New tech coming in seed traits
Vern Hawkins paused when asked about the largest agricultural innovation of the past 20 years.
Digital agriculture? Agricultural chemicals? Machinery?
Nope, nope, and nope. “The biggest one is the seeds and trait market,” says Syngenta’s crop protection president. When paired with innovations Syngenta has made in crop protection, digital agriculture, and biologicals, seeds and traits have greatly impacted the types of crops grown in different environments, he says.
These days, though, traits are hitting turbulence. Cracks are forming in Bt traits that enable corn hybrids to resist corn rootworm. Weeds also resist multiple herbicide sites of action, including herbicides used in older herbicide-tolerant systems featuring glyphosate and in newer herbicide-tolerant traits. University of Tennessee 2020 greenhouse and field research suggests Tennessee now hosts dicamba-resistant Palmer amaranth.
On the flip side, opportunities abound. The XtendFlex system – with soybeans that tolerate dicamba, glyphosate, and glufosinate – will debut in 2021. With the exception of Italian ryegrass in California and Oregon, no weed in corn and soybean systems has yet resisted glufosinate (Liberty).
Bayer Crop Science plans to build on this and gradually increase to six-way herbicide tolerant stacks by 2030.
Farmers in selected counties can also apply BASF’s Alite 27 in 2021. It’s the first Group 27 herbicide – applied on a preplant and preemergence basis– that matches GT27 and LibertyLink GT27 soybean varieties.
Farmers can also opt for the Enlist weed control system. It confers herbicide tolerance to a new 2,4-D formulation – 2,4-D choline – and glyphosate in corn, soybeans, and cotton and “fop” herbicides in corn. Herbicide options include Enlist Duo, a mix of glyphosate and 2,4-D choline. Enlist One is straight 2,4-D choline that can be tank-mixed with qualified herbicides.
In the insect space, Bayer Crop Science, Corteva Agriscience, and Syngenta scientists are developing a novel corn rootworm event using RNA interference (RNAi) technology. Gene editing could also supplement genetically modified traits during this decade.
Traits Are One Component
Traits often garner the glory in the seed world over other attributes. Still, seed decisions made solely on traits can mask other necessary product attributes.
“Herbicide tolerance is often just two to three genes out of 10,000 that make up a soybean variety,” says Ryan Van Roekel, a Pioneer field agronomist.
In some cases, it may be more important to select a variety that resists soybean cyst nematode (SCN) in a field with SCN history, he says.
In corn, Tommy Caltrite, Sunray, Texas, selects hybrids with a trait that resists European corn borer. He often passes, though, on hybrids with traits that resist corn rootworm because he rotates corn with other crops. “That’s a problem you can get into when you plant corn on corn,” he says.
Still, traits remain a valuable tool, says Van Roekel.
“Sometimes, herbicide choice comes first before yield and disease tolerance,” he says. A soybean variety with the best disease traits or yield potential wouldn’t make a dent in a field that’s been plagued by waterhemp or Palmer amaranth, Van Roekel adds.
That’s also the case with insects. Corn rootworm had been quiet for several years, but in 2020, it returned, ravaging roots and slicing corn yields in many areas.
“In this area with lots of corn-on-corn acres, there were many fields that needed [rootworm] traits,” says Bill McClure, a Nebraska-based Pioneer agronomist.
In most cases, Bt traits that enable hybrids to resist corn rootworm still work well.
Still, entomologists have confirmed resistance to or found unexpected root damage to all four types of Bt proteins that include the:
- Cry34Ab1/Cry35Ab1 Bt protein present in the Herculex RW trait contained in SmartStax, AcreMax XTreme, Agrisure 3122 hybrids, and Qrome products.
- Cry3Bb1 Bt protein found in products such as SmartStax, SmartStax RIB Complete, VT Triple PRO, and VT Triple PRO RIB Complete.
- mCry3A Bt protein included in Agrisure Viptera 3111, AcreMax TRIsect, AcreMax XTreme, Agrisure Duracade 5122 E-Z Refuge, Agrisure Duracade 5222 E-Z Refuge, Intrasect TRIsect, Intrasect XTreme, and Qrome products.
- eCry3.1Ab protein included in Agrisure Duracade 5122 E-Z Refuge and Agrisure Duracade 5222 E-Z Refuge.
Help is on the way, though. Bayer, Corteva Agriscience, and Syngenta are developing new RNAi technology to manage corn rootworm. In Bayer’s case, the RNAi technology will be part of SmartStax PRO set to launch early this decade. It will form a triple stack when teamed with the Cry3Bb1 and Cry34Ab1/Cry35Ab1 proteins.
Corteva Agriscience is working to launch its next-generation corn rootworm stack featuring RNAi technology with the Cry3Bb1 and Cry34Ab1/Cry35Ab1 Bt proteins. It will be paired with the Enlist herbicide-tolerant trait, pending applicable regulatory reviews and completion of field testing.
Syngenta also is working with RNAi technology and has not given a timeline for product commercialization.
How It Works
RNAi technology can forestall resistance in Bt proteins because it kills corn rootworm differently. “When Bt proteins are ingested by corn rootworm larvae [feeding on corn roots], they bind to the midgut,” says Jody Gander, Bayer technical development manager. “ Larvae then die, he says.
“RNAi technology isn’t a protein, so it doesn’t work in the same way as Bt proteins work,” Gander adds. “With RNAi technology, the larvae ingest the double-stranded RNA that is produced in the plant. This alters a natural process within corn rootworm larvae that causes a specific protein not to be produced. That specific protein is essential for the larvae to survive. Since it’s not produced, the larvae dies.”
RNAi technology will follow a regulatory path similar to Bt products, says Tony Klemm, Corteva Agriscience corn global portfolio leader. Resistance management will be part of RNAi products, just as they have been with Bt proteins, he adds. That’s why RNAi will be combined with existing Bt proteins.
“Multiple modes of action are the best way to manage resistance,” he says.
The refuge strategy for packages including RNAi will be similar to the 5% refuge-in-a-bag present in current Bt trait packages, says Gander. “We need to make sure we have refuge plants to have susceptible rootworm mate with other rootworm that might potentially develop resistance,” he says. This helps ensure that susceptible offspring result, he says.
Yield drag is always a concern with new products. “With any new technology, there needs to be much research done to ensure the technologies don’t harm any aspect of yield potential,” says Klemm. He adds that Corteva Agriscience has rigorous testing components to detect any yield drag and eliminate before commercial launch.
Where to Use
Price can nix farmer adoption of new seed technology like traits, as it can be more expensive than older technology. In some cases, gleaning a lower seed price by forgoing a trait may not harm yield.
“If farmers rotate corn [with another crop] they might not need a hybrid with a rootworm trait,” says Tim O’Brien, Agrisure traits manager for Syngenta.
Still, planting hybrids with multiple insect-resitant traits often pays if farmers continuously grow corn or live in areas with extended diapause or the western corn rootworm variant, he adds.
Extended diapause occurs when eggs laid by predominantly northern corn rootworm beetles remain dormant in soil over time and hatch during a corn year.
The western corn rootworm variant occurs when females lay eggs on neighboring soybean fields. Larvae that hatch the following year may then feast on corn roots.
“There will always be seed price shoppers,” points out Bruce Battles, Syngenta technical agronomy manager. “I think most farmers, though, are more concerned about finding the right hybrids for their fields. There’s a feeling that at the end of the day, you get what you pay for.”
RNAi Short Course
Here’s an RNA interference (RNAi) technology short course from three Syngenta scientists: Wendy Maddelein, head of Syngenta’s Ghent Innovation Centre; Geert Plaetinck, Syngenta expression and delivery senior group leader; and Matt Bramlett, Syngenta principal scientist.
- RNA-based biocontrols (sprayable application) form a new class of products to control insect pests and to protect crops. RNAi triggers are naturally occurring molecules (dsRNA) that rapidly degrade with a low environmental impact.
- RNAi (RNA interference) naturally reduces or removes the specific expression of an individual protein within a cell. This mechanism helps a cell protect itself from viral attack. In recent years, this phenomenon has been used as a powerful research tool and contributed greatly to the characterization of individual genes and how they interact with each other.
- RNAi used to control corn rootworm targets key transcripts within the insect’s cells. When a dsRNA molecule that matches the transcript sequence coding for a critical corn rootworm protein is ingested by the insect, the impairment of a critical protein kills the pest. These dsRNA molecules can be delivered via a spray formulation similar to traditional crop protection active ingredients or via transgenic production within a crop plant.
Multiplexing with Gene Editing
Differences abound between genetic modification and gene editing in crops. A big one, though, is numbers.
Single genes from foreign material that genetically modify a crop plant work well for solving a specific problem, such as spurring a plant to resist an insect.
Increasing water or nitrogen efficiency, though, is much more complex and requires multiple – in some cases dozens – of edits to a plant genome in the gene editing process, says Ponsi Trivisvavet, CEO of Inari, a Cambridge, Massachusetts, firm that’s using gene editing with other new breeding techniques to develop new and enhanced varietal attributes.
“When we talk about gene editing in our strategy, everything is about multiplexing,” says Trivisvavet.
Improving nitrogen and water use efficiency, yield, and changes to plant architecture requires multiple and simultaneous plant changes. These changes are complex, and require many changes, or edits, to the plant’s genome, she says.
Inari uses a process called predictive design – a statistical technique used to predict future behavior and outcomes – to break down complexity. For example, 1.2 million possible combinations can result among interactions between 13 soybean genes, says Trivisvavet. Sorting out these combinations using conventional means would be almost impossible.
“We use predictive design to more accurately predict crosses, optimize, and prioritize gene networks with a smaller number of samples rather than working in larger sets,” says Trivisvavet.
Inari is focusing on getting its technology to farmers by working with independent seed companies. This also coincides with Inari’s long-term plan of using gene-edited attributes to boost corn and soybean yields .
Gene-edited products also can be produced at a lower cost than genetically modified traits. “It can cost up to $250 million to develop a trait,” says Trivisvavet.
Gene-edited technology also used to be expensive. “Five years ago, it would cost around $100,000 to sequence a gene,” she says. “Now, the cost is down to $200.”
Such products also have a shorter regulatory path than do GMOs [genetically modified organisms], she says.
New Strategies Needed
Gene editing holds promise in many areas, says Tim O’Brien, Syngenta Agrisure traits manager. In others, though, genetically modified traits still are key.
“Gene editing to get insect resistance is probably not going to be possible,” he says. That’s why companies will need to use all tools – Bt traits, RNAi technology, gene editing, and biologicals – to bring solutions to farmers, he adds.
“We want to use a solutions approach vs. a ‘Here’s a trait, this will fix your problem,’ ” says Travis Kriegshauser, Syngenta strategic marketing manager for soybeans. “If not, the trait won’t last due to resistance. Biology evolves.”
Every time science spawns new technologies like RNA interference or gene editing, companies need to sell farmers on adopting it.
They aren’t the only ones who need convincing, though. Consumers also have to be persuaded, something the industry didn’t do when genetically modified technology first surfaced, says Brett Begemann, Bayer Crop Science chief operating officer.
That’s changing. “There is still a noisy edge on both sides, but the base in the middle is bigger,” he says. “When I go to conferences outside of agriculture, the conversation about GMOs [genetically modified organisms] hardly comes up.”
He says this reflects continued engagement with consumers, but also the evolution of science, which bodes well for technologies like gene editing and RNA interference.
“At the end of the day, we’re all trying to do the same thing: determine how to feed the people of the world with a healthy and nutritious diet and take care of the planet while doing it,” he says.