WASHINGTON (Reuters) - A mutation in a single gene can turn hybrid tomato plants into super producers capable of generating more and much sweeter fruit without genetic engineering, scientists said in a study released on Sunday.

Galdino Gonzalez, 56, shows tomatoes to Reuters journalists at an urban vegetable garden in the Iztapalapa district, Mexico City, July 31, 2008. REUTERS/Henry Romero

The study also showed that using classic plant-breeding techniques can boost yield as dramatically as using genetically modified organisms, said researcher Zachary Lippman of Cold Spring Harbor Laboratory in New York.

The mutation in one copy of the gene boosted tomato yield by up to 60 percent and increased sugar content, Lippman and colleagues reported in the journal Nature Genetics.

“When this gene is only working at half speed ... there’s this rebalance of growth that’s happening that occurs across the entire plant that gives you this increase in yield,” Lippman said in a telephone interview.

The yield-boosting power of the gene known as Single Flower Truss, which controls when plants make flowers, worked in different varieties of tomatoes and in different environments, Lippman said.

“No matter what soil type, no matter what sort of irrigation you give it, no matter what fertilization you give it, you’re always having some sort of effect,” he said. “We try to keep it conservative and say 60 percent. Sometimes it’s a little lower, sometimes it’s even higher.”

When both copies of the gene are working, the result is a completely normal plant. “But when one copy is working, you see the heterosis. This is the magic of the discovery,” Lippman said.

Heterosis, or hybrid vigor, is the genetic mechanism that makes offspring of cross-bred plants more vigorous than their parents.

Lippman said the finding could have significant impact on agriculture, and the next step was to look at the effect in corn, soybeans and other crops.

“Our concept about using mutations in the hybrid condition extends beyond tomatoes, and I bet that if people start using this ... in other crops that they find similar effects,” he said.

Lippman and colleagues at the Hebrew University of Jerusalem in Rehovot, Israel, screened gene mutations in more than 5,000 hybrid tomato varieties.

Plants were tested in fields in multiple locations in 2008 and 2009. Some farmers used pesticides and other did not. The boost in crop yields was consistent, Lippman said.

Tomatoes were one of the first genetically modified crops. Monsanto’s “Roundup Ready” tomato, which resists the effects of the weedkiller Roundup, was first marketed in 1996.