Strawberry losses from Fusarium wilt could become less of a threat after UC Davis researchers discovered genes that are resistant to the deadly soil-borne disease.
The findings, published in the journal Theoretical and Applied Genetics, are the culmination of several years of work, and the discovery will help protect against disease losses, said Steve Knapp, director of the Strawberry Breeding Program at the university.
“What we’ve accomplished here is important and valuable to the industry and will protect growers,” Knapp said.
Strawberries are a key crop in California, where about 1.8 billion pounds of the nutritious fruit are grown each year, accounting for about 88% of what is harvested in the United States.
Finding the genes could prevent a Fusarium wilt pandemic.
“The disease has started showing up more frequently across the state,” said Glenn Cole, breeder and field manager for the Strawberry Improvement Program. “Once wilting sets in, the plant just collapses. You have total extinction.”
looking for resistance
UC Davis scientists examined thousands of strawberry plants in the university’s nursery and took DNA samples. They then used genetic screening and developed DNA diagnostics to identify genes that are resistant to the parent race of Fusarium wilt.
“Genes have been floating around in strawberry germplasm for thousands of years,” Cole said, but no one worked to identify them.
This latest development brings “the strawberry into the 21st century in terms of solving this problem,” Knapp said.
Protecting future crops
This work means that breeders can introduce the resistant gene into future strawberry varieties. This fall, the program will release new cultivars that have the Fusarium wilt resistance gene. And DNA diagnostic tools will help breeders respond to new Fusarium wilt variants that develop.
“There will be new threats and we want to be prepared for them,” Knapp said. “We want to understand how this works in strawberries so that as new threats emerge we can address them as quickly as possible.”
“If you don’t have fusarium resistance, you’re done,” Cole said. “The disease could be present more than you think.”
Traditionally, Fusarium wilt has not been a problem, but when the fumigant methyl bromide was phased out in 2005, things changed. The disease was in the soil and without the fumigant, wilt cases increased, especially in areas where crops were not rotated.
Obtaining new varieties
Knapp and Cole have informed the industry of current strawberry varieties that have resistance so they can select plants with that extra protection. The new resistant varieties that will come out later this year will be suitable for several growing seasons.
“It’s a big deal,” Cole said. “Everything is incremental in plant breeding, but it’s a big deal.”
Plant scientists have been breeding strawberries at UC Davis since the 1930s and have released more than 60 proprietary varieties through the public breeding program.
All of the work occurred at UC Davis. Dominique Pincot, Mitchell Feldmann, Mishi Vachev, Marta Bjornson, Alan Rodriguez, Randi Famula, and Gitta Coaker from the Department of Plant Sciences, and Thomas Gordon from the Department of Plant Pathology contributed to the research, as did Michael Hardigan and Peter Henry, who are now at the US Department of Agriculture’s Agricultural Research Service and Nicholas Cobo, who is at the Universidad de La Frontera in Chile.
The research was funded by UC Davis and grants from the USDA National Institute of Food and Agriculture’s Specialty Crops Research Initiative.