The world of plant breeding has been turned on its head in recent years with the prospect of gene editing. Already, researchers are busy working to define traits to create better crops using a technique that can significantly advance crop genetics. Trouble is, getting that new trait back into elite crops still means backcrossing the old-fashioned way and growing out plants for seeds. That could be changing if a breakthrough announced by Syngenta crop breeders gets wider use.

For many who have followed news of gene editing and the rise of tools like CRISPR-Cas9, there’s one fact that’s often left out. “In applying genome editing tools to crops, it’s not that simple,” explains Qiudeng Que, senior group leader, Syngenta Seeds research. “In crops, the cell wall is very tough, which makes changing plants more difficult.”

Getting the gene editing machinery into a plant means getting through that cell wall, so the editing can be done. Que says the biology of plants made direct introduction of editing machinery hard. Only a very limited number of crop varieties can be directly edited; usually, they are the ones with poor agronomic performance. So that meant using a model crop variety — perhaps a parent inbred that didn’t have all the desirable traits — to edit. That plant might get the enhanced trait for yield or some output factor, but it is necessary to get that same trait into many other elite hybrids or varieties for growers in different regions.

Que explains that plant breeders still had to do several generations of backcrosses to get the edited trait into elite lines. “That takes time — two or three years to bring that edited gene into your target crop varieties,” he says.

That may be changing, with news that Syngenta researchers have detailed their discovery of a genome editing technique called haploid induction editing. The company is calling it HI-Edit technology (they’ve even trademarked it). A paper with results of the work was published recently in Nature Biotechnology.

Rethinking breeding

HI-Edit refers to haploid induction, a reproductive process that occurs naturally in wheat, corn, barley and tobacco. The researchers have combined that with genome editing tech like CRISPR-Cas9.

“The doubled haploid technology has been in place for many years. It is used for doing breeding for making pure lines,” Que says. Many companies  use this technology to improve parent inbreds and keep moving the bar on crop productivity.

However, with HI-Edit, using genome editing combined with haploid induction means a specific trait can be put into a target crop at any breeding stage — including existing elite inbreds.

Que explains that researchers can do the editing right in the induced haploid that goes into the breeding program. “The magic is, the haploid induction is variety-independent. And after the haploid induction, only the genome from the female is retained; and the inducer genome, including the editing machinery, gets eliminated naturally.”

A single step

That means the elite female carries the trait enhancement, and that allows moving the trait into commercial-ready crops a lot faster. “This is a quantum change, combining editing with breeding [in a single step],” he says.

Adds Tim Kelliher, a Syngenta fellow and lead author of the paper: “Few commercial crop varieties are responsive to direct genetic manipulation; so, until now, we have had to use techniques that take several years and cost millions of dollars. With this new method, we can harness the potential advanced genome editing technologies to make genetic improvements faster in the varieties growers want.”

Initial work has occurred in field corn and sweet corn, but there is evidence the technique could work with wheat. And the company is also working on the vegetable side, with cruciferous vegetables like cabbage, broccoli, cauliflower and kale. There could also eventually be breakthroughs in soybeans and tomatoes.

Gene editing offers a lot of promise to advance plant breeding in new ways. Tools like HI-Edit show that the science continues to advance, with a range of potential for agriculture. You can see an abstract of the article, "One-step genome editing of elite crop germplasm during haploid induction,” at its Nature Biotechnology webpage.