Like so many stories in the history of fruit breeding, the origin and development of Oregon State University's (OSU) purple tomato "Indigo Rose"  spans many continents and decades in the making.

OSU horticulture professor Jim Myers says the fruit's genisis began in the 1960's when two breeders, from Bulgaria and the U.S., cross-cultivated tomatoes with wild species from Chile and the Galapagos Islands.

Graduate students worked with Myers to cross lines carrying wild tomato species' genes to develop the new variety.

"It is the first improved tomato variety in the world that has anthocyanins in its fruit," he says.

"If you want a really, really purple tomato that can be as black as an eggplant, give Indigo Rose a try - other so-called purple and black tomatoes have the green flesh gene, which prevents normal chlorophyll breakdown.

"A brown pigment called pheophytin accumulates and has a brownish color that makes a muddy purple when combined with carotenoids."

The professor highlights that many wild tomato species have anthocyanins in their fruit, and until now most home gardens have only had the beneficial pigment in their inedible leaves and stems.

The novelty variety is intended for home gardens and the fresh market, and is now available in seed catalogs. As the Indigo Rose is self pollinating, seeds saved will grow true and not produce hybrids.

Jim Myers opens an Indigo Rose purple tomato

"It's also important to know that genetic engineering techniques are never used to develop these lines - these tomatoes are not GMO (genetically modified organisms)," says Myers.

An ORU press release said the Indigo Rose is a full-season cultivar in Oregon with an average first ripe date about 91 days after transplanting, which is about 13 days later than 'Siletz' and eight days later than 'Early Girl.' Its fruit yield is similar to the heirloom cultivar 'Black Prince'

Taste and appearance

Myers warns growers not to pick the variety too soon to ensure that acids and sugars develop fully, while exposure to light is what brings on the purple color. He adds that visual clues won't be there which means it is easy to harvest too early, but under the right conditions it is a good tasting fruit.

"People are passionate about their tomatoes - the purple color draws their interest and because it's extraordinary, people tend to expect impressive flavor as well," he says.

"It does have a good balance of sugars and acids and tastes just like a tomato. Anthocyanins are essentially tasteless.

"While other fruits, such as blueberries, have higher concentrations of anthocyanin, tomatoes are consumed practically daily in the United States."

The release said cherry tomatoes were likely next on the list of Indigo anthocyanin series to be bred over the next three years.

Photos: Tiffany Woods

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