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For Tomatoes, There's More Than Meets The Eye

A pile of tomatoes stacked like building blocks at a grocery store.

Strangely, one of the main determinants of a tomato's commercial success is not its flavor, but its hue. We consumers know what we want, and that's bright, consistent red.

Although mottling can be an indicator of many unsavory things – disease, rot or nutrient deficiency -- this isn't necessarily the case. And uniform crimson isn't always a good sign either.

For the past 70 years plant breeders have catered to our aesthetic preferences, selecting for a genetic mutation called uniform ripening. This mutation conforms tomato color to society's wishes, but according to a recent study published in Science, it also creates less visible changes in the fruit, such as reduced sugar and antioxidant content.

This, in turn, leads to muted flavor and diminished health benefits.

Breeding For Beauty

In immature tomatoes, the uniform ripening mutation expresses as even, light-green coloration, which stems from reduced chlorophyll content. Chlorophyll -- the light-absorbing green pigment in plants -- is critical for sugar production, and so less chlorophyll means less sugar.

Ironically, uniform ripening also reduces levels of a red and possibly healthful antioxidant called lycopene.

Without the mutation, immature tomatoes appear darker around the stem area -- a feature known as "green shoulders." This early variegation often persists as fruits ripen, eventually resulting in oddly-colored but perfectly fit, antioxidant-rich, piquant tomatoes.

Vintage Technology

To boost future tomatoes' tastiness, some researchers are looking to the past for inspiration.

Harry Klee, a professor of horticulture at the University of Florida who was not involved with the study, is optimistic over the viability of heirloom varieties lacking the uniform ripening mutation.

"What I tell people is, we can have 100 percent of the flavor [of heirloom varieties] with 80 percent of the agricultural performance of the modern varieties, with very little work," he says.

The recent sequencing of the complete tomato genome should help with these efforts, according to Dr. Jim Giovannoni, a plant geneticist at Cornell University who co-authored the uniform ripening study and contributed to the tomato genome report.

Read More:

  • Uniform ripening Encodes a Golden 2-like Transcription Factor Regulating Tomato Fruit Chloroplast Development (Science)
  • How The Taste Of Tomatoes Went Bad (And Kept On Going) (NPR)
  • Flavor Is Price of Scarlet Hue of Tomatoes, Study Finds (NY Times)
  • More Genes Than Humans: The Tomato Decoded (NY Times)

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