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Finally this hour, a break from Supreme Court coverage. We're going to take a few minutes to talk about the state of the modern tomato. Today, scientists revealed a small but intriguing chapter in the story of the tomato, a story, some would say, of its downfall. NPR's Dan Charles explores how the tomato came to be so abundant, yet lost so much of its taste.

DAN CHARLES, BYLINE: We'll start with the old tomatoes, varieties that people grew a century or more ago. Some people still grow them, like Eric Rice at Country Pleasures Farm near Middletown, Maryland.

ERIC RICE: Valencia, the one here in the front, for example, is a tomato from Maine, the orange one.

CHARLES: It's been around, he thinks, since the early 1800s. He grows others called Cherokee Purple, Dr. Wyche and one called Mortgage Lifter.

RICE: When I was in North Carolina, actually, I first started tasting heirloom tomatoes when I was in graduate school and decided I really liked them.

CHARLES: He liked the vivid taste. He liked the unusual colors: yellow, orange, purple. Now, he grows them to sell to customers at a farmers' market in Washington, D.C. But Rice admits all that tomato personality can make heirlooms harder to grow and sell.

RICE: Heirloom tomatoes don't ship very well because they're softer. And frankly, they are all different kinds of shapes and sizes.

CHARLES: So they're harder to pack. And there's something else you'll notice as these tomatoes start to get ripe. The part of the tomato near the stem, what's called the shoulder of the fruit, stays green longer.

RICE: I think it is an issue for some consumers because folks do buy with their eyes, and green shoulders also mean that it's not entirely ripe or not as soft and as tasty there.

CHARLES: Now, those green shoulders turn out to be surprisingly significant. In this week's issue of the journal Science, scientists are reporting that when people eliminated them from modern tomatoes, some of the tomato's taste disappeared too. This is how it happened. Sometime before 1930, back when all tomato plants were heirlooms, a tomato grower noticed a plant with distinctive fruit. These tomatoes turned red from stem to tip in a uniform way, no green shoulders.

It was a new genetic mutation, and it seemed like a great thing. Somebody saved seeds from that plant and grew more. Plant breeders used those plants to crossbreed with other tomato varieties to get rid of their green shoulders too. Ann Powell at the University of California, Davis, says this uniform ripening trait spread through the entire tomato industry.

DR. ANN POWELL: It's a little bit hard to find a variety that's in modern production that doesn't have it.

CHARLES: Powell is one of the scientists who now has discovered the genetic change responsible for uniform ripening. She admits she sort of stumbled across it by accident.

POWELL: The experiment was completely backwards in how we did it.

CHARLES: She was looking at some genetically engineered tomato plants that were created so that scientists could study the effects of different genes. Each plant contained an added gene from another plant, a little weed called Arabidopsis that plant scientists like to work with. Powell noticed that one of these added genes resulted in green tomatoes that were really dark green. It struck her as odd.

POWELL: The leaves were not dark green. It was only the fruit that were dark green.

CHARLES: Powell thought to herself this gene seems to have an interesting effect on how tomato fruit ripens. I wonder if some tomato plants have their own version of this dark-green gene. She and her colleagues looked for it, found it, and by coincidence, so did some other researchers on the other side of the country at Cornell University. They discovered that this natural tomato gene, when it works properly, produces those green shoulders on tomatoes. And the darker green color comes from extra chlorophyll, which is what converts sunlight into sugars for the plant. In fact, those dark green shoulders were making these old tomatoes sweeter and creating more flavor. The uniform ripening mutation disabled this gene.

DR. HARRY KLEE: We find out that, oh, my goodness, this is one of the factors that actually has led to the deterioration of flavor in the commercial tomato.

CHARLES: That's Harry Klee, a professor at the University of Florida. Klee has been exploring the chemistry and genetics of tomato taste. He says tomato breeders made a lot of compromises like this over the years as they created tomato plants that produce more fruit and firmer, more rugged fruit. But now, Klee says, with some of this new science, we have a chance to undo some of those decisions.

KLEE: You know, so what I tell people is that we can get 100 percent of the flavor and 80 percent of the agricultural performance of the modern varieties with very little work.

CHARLES: We can start with some of the best heirlooms and then bring in some of the disease resistance genes that modern varieties have, increase yields at least a little bit. Consumers may have to change their expectations, Klee says. They may have to get used to tomatoes with green shoulders, for instance.

KLEE: They're going to have to go in and say, oh, look, that one's got that little discoloration at the top, that means it must be good.

CHARLES: But these tomato plants probably won't produce as big a harvest, Klee says. So the only way they're likely to show up in your local grocery store is if consumers can recognize them and pay a little more for them. Dan Charles, NPR News.

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