Classical plant breeding has a lot of baggage. If a plant breeder identifies a key trait in an exotic version of the plant, moving that trait into established germplasm is a long, drawn out process of working to strip away the excess genes to get that desirable trait into the final plant. A newer approach is in the works maximizing genetic knowledge that makes that process a lot easier and DuPont Pioneer recently announced what it sees will be the first commercial ag product to use the technology.

The new tool for plant breeding is CRISPR-Cas, which allows a breeder to very precisely remove or add a specific trait within a crop genome right where it belongs with no baggage. "Using this process we can move desirable alleles from a variety - a good allele for a particular trait - in one step, into an elite inbred," explains Neal Gutterson, vice president, research and development, DuPont Pioneer.

Stepping back for a moment - CRISPR stands for clustered regularly interspaced short palindromic repeats - and combined with Cas a specialized enzyme for cutting DNA - the technology allows for targeted genome editing using guide RNA to specifically place traits into the genome directly. While it's a little jargon-filled for geneticists, it is a very promising technology for enhanced efficiency in the plant breeding world.

Gutterson tells Farm Industry News that this technology at DuPont Pioneer is used for bringing corn genes into corn. "[With this technology] we have two kinds of options for waxy corn - not bringing in any traits, but rather deleting genes; or bringing to an elite inbred just the waxy genes," he explains. "We can take a trait from one corn plant and place it where it normally would be in another corn plant directly, this is a very powerful option for us."

This is the next step in advanced plant breeding, Gutterson says. With the technology the company can very precisely grab a needed trait from even the most exotic corn variety - say a 12-foot hybrid that performs well in Brazil, and insert it into an inbred designed to perform in central Iowa. Perhaps that Brazil-corn trait offers protection from disease or enhanced drought tolerance. With CRISPR-Cas it's possible to grab only the trait you want.

Why waxy?

DuPont Pioneer's announcement was for Waxy corn. This is an identity-preserved line that's planted on about 500,000 acres a year and Pioneer is a leading supplier of these hybrids which produce a specific high amylopectin starch content popular in wet milling with both food and non-food uses. Trouble is waxy hybrids just don't yield like their non-waxy cousins.

"The next generation of waxy hybrids developed with CRISPR-Cas will represent a step-change in how efficiently we bring elite genetic platforms of high-yielding waxy corn to our customers," says Gutterson.

He explains that waxy corn is currently developed from 100-year-old germplasm and non-elite genetic material, noting that the laborious process of backcrossing creates a yield lag. Yet with the CRISPR-Cas tool, Pioneer will be able to more easily create waxy corn from elite germplasm on par with current non-waxy hybrids. "This will impact yields and the products we deliver to the market," Gutterson says. "We'll be able to deliver the same familiar waxy maize at higher yield, with better performance."

The key is that with CRISPR-Cas, Pioneer removes the waxy gene directly from elite inbreds, and nothing more. This is an advanced breeding technique that brings a next-level potential for corn, and other vital crop plants.

USDA and regulation

CRISPR-Cas involves working at the genomic level of plants, but the finished plant produced with the tech "is indistinguishable from plants that could result from native genome variability or be developed in a conventional breeding program," according to a letter Pioneer submitted to USDA last December.

In that same letter, Pioneer made the case that CRISPR-Cas derived plants should not be considered a "regulated article" because "it does not contain any inserted genetic material" from a donor organism, recipient organism or vector or vector agent listed as part of the USDA Animal and Plant Health Inspection Service regulations for genetically engineered plants. Pioneer also pointed out that it is unlikely that waxy corn would become a plant pest within the meaning of the Plant Protection Act.

The good news for Pioneer is that USDA concurred with the assessment stating that this next generation waxy corn would not be regulated by the agency Biotechnology Regulatory Services. It is not a GMO.

However, Gutterson says that's just the beginning of the global regulatory conversation on CRISPR-Cas tech and its use by Pioneer. "This is a global issue and how it is regulated and perceived in all markets matters. We're working with regulatory agencies to help them understand what we're doing and we're in discussions with them," he notes.

The conversation about this type of plant breeding work involves a wide range of stakeholders including regulators and non-governmental organizations too. "We are involved with a lot of folks in our outreach to understand how people feel about this technology," Gutterson explains. "We're working to develop collaborations and partnerships with more international agriculture organizations; we think there's tremendous opportunity with this technology in the developed world and the developing world."

Global implications

In fact, Gutterson notes that this work could help advance breeding for improved hybrids and varieties of plants that would be more productive, disease resistant, drought tolerant and stand up to production practices even for small-holder growers in the developed world. "We're partnering with some international organizations to look at the application of CRISPR-Cas to their crops."

Pioneer has a vast library of exotic germplasm for its principle crops, and this new technology "accelerates our ability to use more of our germplasm, and its more valuable to the international organizations and the collections they have," Gutterson says. 

There are global challenges to crop protection from rising water salinity, increased drought, and advancing disease issues that work to beat back crop yields. Plant breeders have been in a constant battle against those forces for decades. With CRISPR-Cas it looks like there's a new tool available that could help push against those yield-robbing external forces in new ways.

Pioneer previously announced strategic agreements for research collaborations and intellectual property licenses with Vilnius University and with Caribou Biosciences. These are combined with DuPont’s own IP, technology capabilities, infrastructure and scientific expertise that are being applied in order to advance CRISPR-Cas.