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Bean varieties with resistance to sclerotinia
Sclerotinia is by far the most important disease in beans in Northwest Europe. The disease is becoming increasingly difficult to control with crop protection products alone. But help from breeding is on the way: the first intermediately resistant bean varieties – varieties with improved resistance to sclerotinia – are on the way.
Bayer spoke about this with Arie Oppelaar, bean breeder at Bayer Vegetables.
First of all, what role does Dutch bean cultivation play in your breeding program?
"To be honest, that role isn't that significant. Beans are an important vegetable crop worldwide, with many different product types and processing purposes within them. Within Europe, Italy, France, and Poland are major bean-producing countries. At most, a few percent of European beans are grown in the Netherlands. Our focus is therefore primarily outside the Netherlands, although it's certainly not that we don't consider the Dutch market important. With our best-known variety, Cadillac, we still have a decent market share in the Netherlands, and with our new varieties, Honolulu and Clermont, we have two excellent successors ready. In that sense, we will certainly continue our efforts to support Dutch bean cultivation."
What are the most important breed characteristics for the Dutch market?
Here, when it comes to runner beans, it's primarily about yield. If it's not stable and above average, your variety doesn't really count. Uniformity is also important. For the fresh market, beans with a diameter of around 8 millimeters are particularly desirable. Storage and flavor also play a role. A well-developed and strong root system is an increasingly important characteristic. This is fueled not only by greater extremes of heat and drought, but also by increasingly strict fertilization standards and the designation of NV (Dutch agricultural land) areas. Therefore, resilient and stress-resistant varieties are becoming increasingly popular.
What about disease resistance? Which ones are important in this regard?
By far the most important disease in Northwest Europe—and certainly the Netherlands—is sclerotinia. This fungus can cause significant damage to crops, especially under humid conditions. Plants turn pale white and rot. The familiar black sclerotia, also known as rat droppings, develop in the affected stems and pods. Although Dutch growers currently have sufficient resources available to control the disease, the industry is increasingly facing customers who want zero residue on the final product. This puts particular pressure on subsequent spraying before harvest.
What role can breeding play in the fight against sclerotinia?
"From a breeding perspective, we can offer assistance with a range of intermediately resistant varieties. These are varieties that, in short, fall somewhere between susceptible and highly resistant (or immune), a kind of improved resistance to sclerotinia. Currently, these varieties are still in the pre-commercial phase; we expect them to be available for practical use in a few years. In the first four trial years, these varieties performed well against sclerotinia. In a crop rotation with few host plants and no irrigation, they even appear to be fully organic. Within conventional farming practices—where beans are almost always irrigated—we see that combinations with the timely application of Luna Privilege followed by the biological agent Serenade yield excellent results. We therefore see this as a future scenario: a combination of an intermediately resistant variety with the most sustainable possible use of crop protection products."
To what extent will this scenario be adopted in practice?
As long as growers can still rely on chemicals, a large proportion will continue to do so for a while. But if pressure from supermarkets—and therefore also from processors—continues to increase towards zero residue, developments can move quickly. I expect that the integrated approach to sclerotinia—with an intermediately resistant variety and targeted crop protection with synthetic and biological agents—will become the foundation for sclerotinia control in the coming years.
