CRISPR rolls along with tools breeders use

Why do some individual plants live longer in the field after others died off? Why do some individual plants yield better? Why do some naturally resist disease that destroys others?

These types of questions are best exemplified by the history of rust-resistant Selkirk wheat.

In 1930, Moseph McMurachy found two heads of rust-free wheat while harvesting. He sowed the seeds and by 1935 had developed six acres. In 1935, a stem rust epidemic wiped out most wheat in his district. McMurachy’s six acres stood almost untouched. By crossing these samples with other varieties, the Selkirk variety evolved and two decades later 150,000 bushels of clean Selkirk seed had been produced.

Plant pathologists today understand the genetics of why one individual plant resists a disease that destroys the adjacent plant. DNA sequences include a gene that invites disease into the plant. If breeders can find that gene and remove it from the DNA sequence, that plant will no longer invite disease to visit.

One technique for identifying and removing that bad gene is called Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR).

North Dakota State University plant pathologist Audrey Kalil says CRISPR is like having a scissor that can surgically remove the DNA you don’t want. Breeders have developed new varieties of canola and flax and are working on vegetables and other crops.

“Plant scientists are looking for ways to help plants withstand infection,” Kalil said.

“One of the best ways to fight disease is to find plants that seem to have their own natural resistance. These are the plants that are still in the field after others have died or that yield well when others can’t.”

However, once these plants are identified, successful breeding from them can take a decade or more using conventional techniques. That means more years of crop destruction in the interim.

“CRISPR is just a very complicated name for a ‘coping mechanism’ by bacteria,” Kalil said.

“CRISPR is an approach that doesn’t require the addition of foreign DNA to a plant. It simply makes a small cut in the plant genome, which will provide big benefits. It’s faster, less expensive and easier to use than older genetic engineering techniques.…

“This results in a plant that lacks the targeted susceptibility gene and thus is resistant to disease. Breeders can then start their process, already armed with a ready-made disease resistant plant. CRISPR greatly speeds up the process to generate disease resistant crops.

Farmers from North Dakota and Western Canada are growing a herbicide resistant canola that was adjusted genetically by San Diego’s Cibus, resulting in non-genetically modified, high performing oilseeds crops.

Massachusetts’ Yield10 Bioscience is improving flax’s omega 3 content using the CRISPR tools.

Pairwise is using it to create designer fruits and vegetables, while Inari believes it can create crops so specific in their adaptations to a location that they will be engineered for each agro-climate and soil type — in other words, for every individual farm.

Benson Hill Biosystems of Missouri announced that it is engineering high-CBD, low-THC cultivars of cannabis for the exploding, legalized pot market.

Breeders and researchers see some of its greatest potential enhancing abiotic and biotic stress tolerance to better understand plants’ natural systems and, through both selection and manipulation, improve their tolerances.

Biotic stress, which is attacks from pests, is thought to result in more than 40 percent of potential yield loss in the field and as much as 15 percent of crop losses annually around the world.

The tool is also being used to improve tolerance to abiotic stresses, such as salinity and drought. Resistance to powdery mildew in cereals has been successfully targeted. Very stable versions of wheat genetics related to the dehydration responsive binding protein 2 and wheat ethylene responsive factor 3 have been created, providing improved tolerance to drought and low temperatures.

Most recently, researchers from China, working with counterparts at the University of Idaho, identified other opportunities to improve breeding efforts in complex, polyploid crops, such as wheat and canola. These include wheat research with lipoxygenase, which confers resistance to fusarium graminearum.

CRISPR-Cas9 systems can also be put to work in plant breeding efforts to improve the visibility of selected or targeted gene locations, allowing scientists to make decisions about what and where to further apply the technology.

“The challenges to our food supply are great,” Kalil said.

“Besides droughts, heat, cold and all the other stresses our crops must cope with, there is also disease. New techniques like CRISPR can help us look forward to a future of more abundant, more sustainably grown food.”

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