The World 's first CRISPR lettuce with increased resistance to fungal disease

White mold is a significant challenge for lettuce production in Norway. In many regions, 20–30% of lettuce crops are regularly affected, and in severe cases, up to 70% of the crop can be destroyed.

This fungus is typically controlled with chemical fungicides, but these are only partially effective and increase the use of chemicals in agriculture. Therefore, researchers have been searching for alternatives.

“We used CRISPR technology to genetically edit iceberg lettuce and make it more resistant to the fungal disease Sclerotinia sclerotiorum. The CRISPR lettuce is a more effective and environmentally friendly alternative to chemical sprays,” explains Tage Thorstensen, a researcher at NIBIO.

Precise Gene Editing

Thorsten elaborates that the CRISPR "gene scissors" is a technology for precise genetic editing.

“We used CRISPR to create a small mutation in a gene to make the plant more tolerant to the fungal disease,” he says.

Master’s student Oda Eline Sandmo Ånesland, from the Norwegian University of Life Sciences (NMBU), worked on the CRISPR lettuce as part of her thesis. She demonstrated that the CRISPR-edited iceberg lettuce is indeed more resistant to white mold compared to unedited lettuce in controlled experiments in greenhouses.

Ånesland tested several lettuce variants with mutations of different sizes and in different locations within the same gene. All showed the same tolerance to the white mold fungus. The experiments revealed that a small mutation in the gene was sufficient to increase tolerance to the fungal disease.

“The lettuce became more tolerant to white mold infection when the gene contained the mutation,” Ånesland explains.

“As far as we know, this is the world’s first CRISPR lettuce with increased resistance to white mold,” she adds.

A ‘Super-Lettuce’

According to Thorstensen, CRISPR technology enabled the development of disease-resistant lettuce in just one year.

“This is a precise and rapid method compared to traditional breeding, where achieving the same level of precision would be impossible. If we had used traditional plant breeding to remove this gene in lettuce, it would have taken at least five years and been less precise. Traditional breeding requires multiple generations, often carrying undesirable traits from parent plants,” he says.

“CRISPR allows us to create lettuce identical to the original. The only difference is a single mutation that makes it resistant to disease. This mutation could have occurred naturally. Therefore, the genetically edited plants are indistinguishable from plants developed through traditional breeding methods,” Thorstensen explains.

Results from greenhouse experiments suggest that this could be a "super-lettuce," more robust against diseases, which could be highly beneficial for future agriculture.

The technology will now be tested on other lettuce varieties.

“Although the CRISPR tool we developed works well, there may be variations between different lettuce varieties,” Ånesland notes. Further testing will determine the broader applicability of the method.

“For other crops, such as potatoes, developing new traits using traditional methods takes 15–20 years. With CRISPR, we could reduce the development time to just a couple of years, with more predictable results. This illustrates the enormous potential of the technology,” Thorstensen emphasizes.

Field testing to follow

The next step is to test the lettuce outdoors.

According to Norwegian and European gene technology regulations, the CRISPR-edited lettuce is classified as a GMO (genetically modified organism), even though no foreign genes were added. This means permission must be sought for field trials, and the lettuce must undergo a stringent approval process to reach the market. The regulations do not consider that these edits involve fewer changes than traditional breeding and include no foreign genes.

“So far, the results are promising in greenhouses, but it’s not guaranteed we’ll achieve the same results in the field. We must therefore apply for permission to conduct field trials, which will likely be the first application for CRISPR-edited plants in Norwegian agriculture,” Thorstensen says.

Looking ahead

Thorstensen explains that there has recently been a public hearing on gene technology regulations in Norway. Many people have provided input, but it’s now up to politicians to decide the way forward.

The situation is uncertain. The EU is undergoing a similar process, with hearings and a European Commission report proposing simpler regulations for gene-edited organisms. However, progress has stalled, partly due to disputes over patent rights and disagreements among EU member states.

A Potential Game-Changer

Thorstensen emphasizes that gene-edited crops could offer significant benefits to agriculture and the environment.

“Our results show that the CRISPR-edited lettuce is more resistant to fungal diseases. Without strict GMO regulations governing gene-edited plants, this lettuce could help reduce the need for chemical sprays and minimize crop losses. This would benefit both agriculture and the environment. However, under current regulations, it’s highly uncertain if or when such lettuce will reach the market in Norway or the EU,” he says.

Thorstensen notes that NIBIO is also working on other projects, such as developing potatoes resistant to late blight and apples that don’t develop scab.

“An application for field trials and possibly approval of the gene-edited lettuce will test the current genetic engineering regulations. If regulatory hurdles block its use, it could slow the development of other crops with even greater advantages for agriculture and the environment. It’s crucial to ask what happens to these opportunities if regulations continue to hinder progress,” he concludes.