July 01, 2025

Enza Zaden releases lettuce varieties with downy mildew resistance

Enza Zaden has released lettuce varieties with downy mildew resistance.Read more about how the varieties can help combat downy mildew.

2 minute read

Enza Zaden has released lettuce varieties highly resistant to new downy mildew, a disease that could harm California lettuce production, particularly in the Salinas and Imperial valleys.

A newly identified race of Bremia lactucae, the pathogen responsible for downy mildew in lettuce, has been confirmed by the International Bremia Evaluation Board – United States (IBEB-US).

Downy mildew is a major disease that can significantly damage lettuce and is also common on cucurbits, a family of plants that includes cucumbers, various melons, squashes and gourds.

Designated Bl: 10US, the race presents a new challenge to U.S. lettuce production, particularly in California’s Salinas and Imperial Valleys, where downy mildew pressure is consistently high.

Bl: 10US has emerged with strength, demonstrating the ability to overcome Dm25, Dm38, Design and several other genes. This reinforces the importance of local research to address the pathogen’s well-documented capacity to evolve rapidly under selective pressure, according to a news release.

The developments highlight the critical role of local research in identifying threats and breeding effective resistances. Breeding vegetable seeds since 1938, Enza Zaden markets local solutions. The company invests in 36 local R&D stations across 24 countries and reinvests 30% of annual sales into ongoing research, Enza Zaden said in the release.

“At our R&D station in San Juan Bautista, CA, we breed for the specific challenges of western U.S. lettuce-growing regions, which includes careful monitoring of pathogen threats,” Julie Butcher, Enza Zaden’s product manager, N&CA open field whole head lettuce and brassica, said in the release. “With B1:10US recently named, we’re pleased to have several highly resistant varieties available now. We are also in the process of advancing more pipeline varieties as we continue to evaluate the impact of the new race and other emerging threats facing lettuce growers.”

Commercially available Enza Zaden varieties showing high resistance to B1:10US include:

Romaine: Adicamp, Almanor and Jara.
Babyleaf: Cavendish, Clearwater, Leucadia (new), Mosslanding (new), Carpinteria and Kinlar.
Eazyleaf: Ezpark, Ezbourne, Ezflor and Asakgreen.

While no crop can be guaranteed free from downy mildew, the combination of highly resistant varieties — such as these from Enza Zaden — together with appropriate chemical protocols and preventive agricultural practices offers the most effective strategy for successful lettuce production, according to the release.

In lettuce, downy mildew Downy mildew causes light green to yellow angular spots on the upper surfaces of leaves and can destroy plant foliage.