University of California, Davis

Setting a Benchmark--Industry Upbeat About Revitalized Strawberry Breeding Program

Strawberry farmers and industry leaders say new science, education, and collaborations underway at the UC Davis Public Strawberry Breeding Program bode well for the quality and sustainability of strawberries in California. The breeding program has launched a large-scale, genetic disease-resistance experiment, added students and staff researchers to its team, and planted strawberry-yield trials on five farms from Ventura to Watsonville.

“It’s a privilege to participate in the novel research they’re doing at UC Davis,” said Tom AmRhein, a longtime member of the California Strawberry Commission and a strawberry producer with Naturipe Berry Growers Inc. near Castroville, site of one yield trial. “Growers are happy about the new focus and positive energy the team is bringing to the program. And because everything they develop is available to all strawberry growers, it protects the viability and sustainability of the whole industry.”

Improving Genetic Resistance to Disease

Strawberries are especially vulnerable to soilborne pathogens, which can destroy an entire crop. Since the 1960s, strawberry growers have depended on fumigants such as methyl bromide—a colorless, odorless gas—to control disease. But methyl bromide has been linked to lung disease and ozone-layer depletion, and will no longer be available after 2016.

UC Davis breeders recently took an important first step in developing a berry with improved genetic resistance to soilborne disease. 

In collaboration with the Department of Plant Pathology, they planted strawberries representing 914 genotypes to begin identifying genes that influence resistance to the fungi fusarium and macrophomina, two common culprits in California, where 80 percent of U.S. strawberry production takes place.

“This will help us identify genes of interest, which we can analyze further in the lab,” said Glenn Cole, a staff research associate with the breeding program.

Integrating Genetic Tools

The program is incorporating advanced genetic tools into its breeding and will conduct DNA fingerprinting on the entire UC collection of germplasm, the living tissue from which new plants can be grown. Integrating genomic information, statistics, and the latest breeding strategies will accelerate the crop-improvement process.

To improve a crop, breeders traditionally cross plants with desired traits and select the best offspring over multiple generations. Some traits, such as flavor and size, are often determined by many genes acting together, while other traits, such as disease resistance, may be regulated by a single gene. Advanced tools help breeders hone in on genes that affect specific traits and select for those genes at an earlier stage.

“Genetic tools are an integral part of a successful breeding program,” said Professor Steve Knapp, director of the Strawberry Breeding Program. “We look forward to helping develop 21st century strawberry breeding.”

Gathering Germplasm

Breeders need genetic diversity of germplasm to develop quality crops that can resist constantly evolving pests, diseases, and environmental stresses. The team is building diversity by collecting strawberry species from the wild and germplasm from the USDA.

The new material will be securely stored with the program’s already impressive collection, including some 1,700 cultivars. Of those 1,700 cultivars, 180 are considered “elite” and will most likely develop into a winning variety. Breeders planted those 180 cultivars on five farms in California, each with its own particular climate and crop-management strategies.

“Each farmer has his own recipe, as I call it, for growing the berries, which is good,” Cole said. “It helps us see how the crop performs in different environments.”

Nurturing Tomorrow’s Breeders

Teaching is now central to the public breeding program, which offers graduate education and will include undergraduates soon. Knapp teaches quantitative genetics, and mentors postdoctoral and graduate students like Dominique Pincot, whose family farms in Santa Maria.

“I heard such wonderful things about Dr. Knapp, and I knew this was where I wanted to study,” said Pincot, who is working on her master’s degree in horticulture and agronomy.

A good berry should be sustainable, disease-resistant, and tasty, too. Postdoctoral scholar Julia Harshman is focusing on flavor.

“We’ll be conducting consumer surveys and working with sensory panels from the Robert Mondavi Institute to make sure all our varieties are full of flavor,” said Harshman, who worked with apples at Washington State University. “Flavor reigns in apple breeding. I want to bring that same attention to strawberries.”

Dan Legard, vice president of research and education for the California Strawberry Commission, applauds the science underway.

“Because all the data and material they develop is public, it will be available to any grower, which is so crucial in today’s competitive marketplace,” Legard said.

And it’s vital to strawberry lovers worldwide, according to Greg France, a family farmer and longtime California Strawberry Commissioner: “The UC Davis Strawberry Breeding Program is setting the benchmark in breeding to improve strawberry quality, yield, and sustainability.”

Reprinted from University of California, Davis CA&ES Outlook Spring/ Summer 2016

Dr. Steve Knapp
Glenn Cole
Dr. Julia Harshman
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