Think about the best strawberry you ever tasted. Sweet, with a flavor that’s a greater-than-the-sum mix of overripe peach, underripe grape, burnt caramel, and a little tang to grab the inside of your cheeks.
Of course, not every strawberry tastes that good. Odds are you’ve been let down. Supermarket berries are bred for size, color, shelf life, and disease resistance. On the agronomical trip to market, strawberries have lost some of their flavor. But a new breed of … er … breeders wants to bring glory back to the strawberry, amping up classical breeding techniques with modern genetics.
Virtually every strawberry you’ve ever eaten is a crossbreed of two species: Fragaria chiloensis, a big-fruited variety that ranges up the western side of the Americas; and F. virginiana, a smaller wild berry that grows from Florida to Alaska.
The crossbreed—called Fragaria x ananassa—used to be smaller, squishier, and more susceptible to disease. Getting them ready for supermarket shelves meant selecting for larger size, firmer flesh, and stronger immunity. Farmers wanted even more: plants that produced in larger quantities, with longer stems so they were easier to pick. Produce section stockers wanted brighter colors and shinier skins. None of those qualities necessarily detract from flavor, but the calculus of selective breeding means not every trait ends up in the final result.
Traits like size, color, disease resistance, and firmness are simple compared to flavor. “When you talk about something like flavor, there are so many components: the texture, the sugar content, the types of sugars, the aromatics,” says Steve Knapp, the new director of the University of Califonia, Davis’s six-decade-old Strawberry Breeding Program. And those sugars (fructose, glucose, sucrose), acids (citric and malic), and fragrant compounds (forget it, strawberries have over 100) come from a sprawling array of genes that interact, modify, and depend on each other to create strawberry-ness.
But that doesn’t mean isolating a flavor trait is impossible. First researchers figure out the chemical structure of the flavor they’re looking for. Then they cross plants where the flavor chemical is strongly selected with blander plants. Sequence the DNA of both parents and the progeny, and you can start sleuthing. “In every aspect of plant breeding there are traits that are highly heritable, which you have a higher probability of finding the genes for,” says Knapp. By cross-referencing the plants’s physical appearances and genomes, the researcher can start building a database of which gene codes for which trait.
That’s the key to building a new kind of strawberry. Once Knapp—or any strawberry scientist, really—has a large enough library of these gene-trait associations, he can start collecting DNA from plants before breeding them together. It’s not genetic engineering, but it does give breeders more confidence that the traits they want will manifest on the other side of the cross. It’s faster, cheaper, and more in control. The stakes are high. Strawberries are the fifth most popular fruit in the U.S.—and a $2.2 billion a year crop—but the industry is always at risk of leaving a bad taste in consumers’ mouths. “Flavor is paramount. If strawberries don’t deliver, people can eat bananas or blackberries instead,” says Mark Bolda, a strawberry expert with the UC Davis program.
Universities have an outsized influence in the strawberry world. Over 60 percent of all the strawberries consumed in the U.S. come from breeds developed at UC Davis. (California as a whole grows almost 90 percent of the U.S.’s strawberry crop.) Most of the rest are developed at the University of Florida’s breeding program, located south of Tampa. Though it’s much smaller than the California program, Florida’s breeding science is already far ahead in terms of flavor genetics. So far, researchers there have found good genetic data for two of those 100 aromatic strawberry compounds. It’s not much, but it’s an advantage. “We’re using the info on the genes to make DNA markers to stack the deck to make for seedlings long before anything goes to field,” says Vance Whitaker, a breeder at the University of Florida’s program.
Neither Knapp nor Whitaker see much of a future for gene editing techniques in enhancing the flavor profile of future strawberry breeds. Besides the complications in marketing anything with a whiff of genetic engineering, flavor is too complicated to engineer in cut-and-paste fashion. “Plant breeding really operates on the entire genome. We don’t have the luxury of working on a gene at a time,” says Knapp. In other words, even though they might be able to isolate a gene responsible for a flavor, they wouldn’t want to breed for it without pulling along all the related genes it blends with as it goes to protein to chemical to mouth-erupting flavor.
But other genetic factors play a role in flavor too. For instance, strawberries don’t ripen off the vine, but in order to ship, a lot of times they have to be picked when they are still firm. “One of the things we have to do is make strawberries that can be picked a little more ripe and still have a shelf life,” says Whitaker. Which means no amount of genetic engineering will ever make a strawberry that tastes better than one picked at peak ripeness and eaten in the sunshine.
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