Dedicated to Downy Mildew Resistance in Leafy Vegetables

24 January 2024, UK: With new races emerging every year, the challenge of controlling downy mildew is far from easy. For growers, it means keeping a keen eye on fields to check for outbreaks. For Syngenta, it means predicting the future to know what kinds of new resistance traits will be needed year after year.

“Downy mildew is one of those traits where not having a resistance trait just isn’t an option,” said Michel de Lange, Syngenta Vegetable Seeds Trait Development Lead. “It can completely destroy yields and growers just can’t afford to take that kind of risk.”

Researchers at Syngenta work tirelessly year after year to bring new resistance traits to market. Because the pathogen evolves so quickly, with new races (strains of the pathogen) each year, it means speed to market, variation of traits, and strength of resistance are paramount to grower success.

High Resistance for Downy Mildew Creates High Quality Leafy Vegetables

Bremia is the pathogen that creates downy mildew in lettuce, while Peronospora is the pathogen in spinach. The complexity of creating strong leafy varieties, in light of evolving races of downy mildew, is impressive.

“When we bring forward a new variety, the resistance needs to be high – not intermediate,” de Lange said. “Because downy mildew impacts the leaves of spinach and lettuce, any visible damage on the plant is not acceptable for our growers.”

To understand resistances, Syngenta researchers use the company’s long history of leafy breeding to understand what traits are impacted when new races emerge, and what options there are to offset that breakthrough race. This means examining not only the genetics within Syngenta’s portfolio, but wild plant material of spinach and lettuce varieties as well.

“Once we understand how the resistance is broken by downy mildew, we can find new varieties to replace the broken one,” he said. “We also use stacked genes to help reduce the risk of future breakthrough resistances.”

More than one mode of action for resistance means it’s that much more complex for a fungal disease like downy mildew to penetrate into the leaf, meaning the plant is more resistant.

Predicting Future Resistances and Bringing Solutions to Growers Quickly

To date, there are 40 recognized unique races of downy mildew – but that’s just the tip of the iceberg. The real variation within those recognized races is much higher, which means the pipeline for new resistance needs to be deep and widely available in our breeding material so we can react quickly to the market needs.

We prepare by continuously monitoring our material for the presence of resistance and we invest in R&D operations to allow us to quickly place the latest discovered resistances into our variety assortment. Once resistance is in the assortment, we scale supplies up quickly for introduction to markets.

Syngenta provides new resistant varieties every year to help offset the challenge of emerging races of downy mildew. These traits take anywhere from three to 10 years to get the newest resistance into our best-in-class assortment.

All in all, it means breeders are predicting the future of lettuce and spinach production – ten years from today.

Protect Downy Mildew Resistance Traits with Integrated Pest Management

While resistance traits give growers new options in the fight against downy mildew, it doesn’t relieve them of the need to scout and proactively manage the disease in fields. A combination of resistant varieties and crop protection can help reduce the spread, or emergence, of new races resistant to today’s control methods.

“The combination of crop protection and resistance genes is the best way for us to protect yields in the long run,” de Lange said. “It helps keep traits viable longer, while protecting yield and quality in fields – a more sustainable approach to managing downy mildew.”

Also Read: DLF to close the R&D site in Landskrona, Sweden

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