Bland Strawberries Get a Genetic Tweak for Flavor

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On the grocery store shelf they look plump, red and delicious. But the first bite can bring disappointment. Strawberries often don’t taste as good as they look, but researchers hope to bring the flavor back to the berries.

The genome of the wild woodland strawberry offers scientists a gene parts list, within which they can look for the genetic underpinnings of flavor compounds produced in the berries, as well as many other things.

For decades, strawberries have been bred for traits that made them look good to consumers, grow well, and handle long shipment times. So, while certain traits, such as berry size, have increased, flavor has been neglected.

Kevin Folta, interim chairman of horticulture at the University of Florida, and colleagues are among those looking to change that.

Finding flavors

There are 21 species of strawberry, some with more complex genetics than others. The cultivated strawberry, first breed in 1765 in the Royal Botanical Gardens in Versailles, France, is among the more complex. Like both its ancestors, it carries eight copies of its genetic code. (By comparison, humans have two.)

In late 2010, researchers reported sequencing the genome of the woodland strawberry. With only two copies of genetic code, this once wild strawberry has become a lab rat for researchers who want to improve the more complex commercial berries.

Flavor is one area of interest. For instance, Folta’s group is pursuing genes responsible for a molecule called methyl anthranilate, which has a grapelike flavor. Commercially cultivated strawberries don’t produce this compound, while wild berries are rich in it.

To identify the genes and biochemistry responsible for this flavor compound, Folta and his colleaguesare tweaking the wild berry’s genetic code, removing the suspect genes or prompting them to become unusually active, to see how production of the compound is affected. They have also attempted to move the flavor-producing trait into the commercial berries by breeding them with wild strawberries.

The results of these crosses indicate they are on to something: “The berries smell wonderful,” Folta said.

For flavor, 1 + 1 = 4 Flavor is actually a complex mix of characteristics. This research focuses on the production of volatile, or easily evaporated chemicals. These become aromas when picked up by the nose, or when released by chewing.

The flavor associated with strawberries is actually a complex blend of fruity- and floral- flavored compounds that mingle and interact with the human sense of smell.

“So, it’s kind of a synergistic one plus one equals four effect,” Folta said.

As a result, adding this compound to the berries doesn’t make them smell more like grapes. Instead, it contributes to a more conspicuously fruity flavor, Folta said.

Other factors, such as sugar content, acidity, and even color also contribute to perception of flavor when eating a berry.

Folta’s lab is also looking at the production of linalool, a compound that evokes Fruit Loops cereal. Other compounds, such as ones that evoke the aromas of pineapples and green grass, are also on their list.

If flavor research is successful, better tasting and smelling berries could arrive on the market in about five years or so. Folta notes that these berries would be the result of conventional breeding, not genetic engineering.

Graduate student Alan Chambers and strawberry breeder Vance Whitaker are also involved in the work.

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