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Solid future for tomatoes; breeders are producing fruit with less water, thicker juice.

Though you might not think of a tomato as watery, most ordinary tomatoes are 95 percent water.

And when you buy a tomato product-a bottle of catsup, a can of tomato soup, or a jar of spaghetti sauce-you're paying the cost of removing that water.

But tomorrow's tomatoes, says ARS scientist Merle L. Weaver, might have less water and more of the compounds called solids that processors condense at the factory. The concentrate, rich in fiber and natural sugars, becomes the starting point for tomato paste and most of the other tomato-based foods at your supermarket.

In the past 3 years, Weaver has produced lab and greenhouse tomatoes with about double the solids content of tomatoes typically raised for the processors' production line. That's a difference you probably can't taste. But it would show up as a "very significant benefit for growers and processors," notes Weaver, who is at the Western Regional Research Center, Albany, California.

Estimates from the tomato industry show that even a l-percent increase in solids content could be worth $70 to $80 million a year.

Better yet, some of the savings might be passed along to shoppers.

Lab techniques Weaver uses might work equally as well to pinpoint tomatoes that have other prized traits. Those qualities could include better flavor, a deeper red color, and juice that's naturally thick, not watery.

Right now, Weaver primarily tests tomatoes for processing. But he also investigates fresh-market tomatoesthe kind sold in the produce section. He works with both standard-size and cherry tomato varieties.

Most of today's commercially grown tomatoes have a solids content of about 5 to 5.5 percent. Yet some of Weaver's lab and greenhouse tomatoes boast a solids count of 8 to 12 percent. One measured an astonishing 15 percent.

Weaver is quick to point out, however, that growers and processors may have to wait another 2 years or more for these promising tomatoes. While some appear to be commercially acceptable already, others have glitches not found in well-established, widely planted commercial tomato varieties. For example, some test plants don't produce enough fruit or enough leaves to protect the fruit from sunburn.

To overcome these problems, plant breeders at Rogers NK Seed Company, a major supplier of farm and garden seeds and partner in the research, are hybridizing Weaver's experimental tomatoes with the company's own commercial breeding stock. Hopefully, the hybrids will inherit the best traits of each parent.

Weaver and technician J. Karen Burton find high-solids tomatoes by methodically screening test tube plantlets for this trait.

To produce plantlets, the researchers fill test tubes about one-third full with a gel-like mix of nutrients. Then they cut bits of leaves and stems from healthy tomato plants and place them atop the gel. Tissue that thrives forms shoots and roots andlater-tiny plants. The indoor culturing of tissue fosters changes-a phenomenon known as somaclonal variation. In this case, the variation the scientists seek is superproduction of solids when the plant matures.

Teamed with the strategy is another tactic: The researchers add a special mix of compounds to the culturing nutrients. Some or perhaps all of these ingredients, says Weaver, apparently interact with the plantlet's mechanism for producing solids. "We're not sure what happens," he admits, "but only the plantlets that can overproduce solids will survive and keep on growing. Those ate the ones we keep."

By increasing the concentration of the blend, the researchers make survival tougher and tougher for plantlets. When the survivors bear fruit, the researchers test the tomatoes, keeping only seeds from those that have a solids content of 7.0 or better.

Neither lab technique-tissue culturing of tomatoes or exposing tissue to screening compounds-is new. But Weaver is likely the first to combine these approaches in a search for high-solids tomatoes.

Seeds from the best of these greenhouse tomatoes advance to outdoor trials. Weaver has relied on Herman Timm, recently retired from the University of California, Davis, to assist with these trials.

At Rogers NK Seed Company, tomato breeder John D. Prendergast directs outdoor tests of plants that are hybrids of ARS tomatoes and his company's best tomato breeding lines. Impressed with the potential of the experimental tomatoes, the company has entered its third year of collaboration with Weaver.-By Marcia Wood, ARS.

Merle L Weaver is at the USDA-ARS Western Regional Research Center, Process Biotechnology Research Unit, 800 Buchanan St., Albany, CA 94710. Phone (510) 559-5760.
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Author:Wood, Marcia
Publication:Agricultural Research
Article Type:Cover Story
Date:Mar 1, 1992
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