Developing Strawberry Resistance to Fusarium Wilt

A Dangerous Pathogen Grows More Virulent

Strawberries in California are threatened by Fusarium oxysporum f. sp. fragariae (Fof), a fungus that causes Fusarium wilt. Evidence of the disease includes wilting, chlorosis, necrosis, premature leaf drop and browning of the vascular system, as well as other symptoms that stunt healthy plant growth and ultimately lead to plant death and yield loss.

While strawberries have some genetic resistance to the pathogen, a new type of Fof, known as Fof Race 2, has emerged that can overcome this resistance. Also troubling, researchers have discovered that Fof Race 1 and Race 2 can produce virulent airborne spores on infected plants, making containment of the pathogen extremely difficult.

Researchers led by Dr. Mitchell Feldmann, assistant professor and director of the Strawberry Breeding program at the University of California, Davis, are using a grant from FFAR’s Rapid Outcomes from Agricultural Research program to identify and promote in strawberries potential sources of genetic resistance to Fof Race 2. They will also study the mobility and virulence of airborne Fof Race 2 to better combat the pathogen.

Fusarium Wilt Threatens Livelihoods & Market Supply

California is the largest producer of strawberries in the U.S., accounting for 90% of the country’s fresh strawberry market. The potential spread of Fof Race 2 across the state will harm growers’ incomes through lower yields or crop loss while also reducing the fruit’s availability and increasing its cost.

Because chemical sprays and fungicides have limited effectiveness against Fof and their use is becoming more tightly restricted in some areas, the need to find, promote and use genetic sources of Fof resistance to develop resistant strawberry varieties is urgent. By better understanding airborne Fof and uncovering new pathways of resistance to the pathogen in the strawberry genome, the researchers hope to mitigate the spread and effects of Fof and ensure a stable supply of the popular fruit.