The tomatoes you grew this summer may be an endangered species.

An obscure bill planted in Congress by Sen. Frank Church (D-Idaho) and Rep. E. (Kiki) de la Garza (D-Tex.) is sprouting into a controversy that pits major seed companies owned by the likes of ITT, Union Carbide and Monsanto against plant scientists and small-farmer advocates.

The bill, a packet of amendments to the Plant Variety Protection Act of 1970, would allow seed companies to patent new varieties of tomatoes, okra, celery, peppers, carrots and cucumbers. They already are patenting other vegetables to protect themselves against competitors.

Critics charge the amendments and the original law itself will lead to outlawing thousands of varieties of common vegetables -- as has happened in Europe. They added that it will create monopolies in the seed industry at a time when many seed companies are being bought out by corporate giants.

In a letter last month to Sen. Thomas Eagleton (D-Mo.), Agriculture Secretary Bob Bergland acknowledged that "the prediction that by 1991 three-fourths of all vegetable varieties grown now will become extinct may prove to be correct. Obsolete varieties are being replaced by improved varieties adapted to extended areas of agriculture."

For scientists concerned about preserving the ancient genetic base of life, such news is ominous. To the seed companies, it is merely the inevitable blossoming of progress -- and profits.

Before vegetable patents, William MacDowell of the W. Atlee Burpee Co. said, research into new and better varieties "was limited by the company's inability to realize a proper return for its investment. . .

"Unlike . . . a writer whose work could be copyrighted or the inventor whose genius could be protected by patent, the seed researcher had new varieties pirated by competitors who merely reproduced them without any compensation to the originator," he told a House Agriculture subcommittee.

Burpee, owned by ITT, is backed by the Washington-based American Seed Trade Association -- and its 600 companies -- which persuaded Church and de la Garza to introduce the legislation in January.

"We have a seed industry in Idaho," explained a Church spokesman.

In introducing the bill, Church told the Senate, "A fine example of the beneficial effect of the Plant Variety Protection Act can be found in the development of the sugar snap pea. This pea is an entirely new vegetable developed by Dr. Calvin Lamborn of the Gallatin Valley Seed Co. in Twin Falls, Idaho."

However, on the House side, the unexpected controversy over the bill seems to have dampened enthusiasm. "The only reason we put it in was because the seed trade and the Agriculture Department wanted it," a House staffer said. If it would cause genetic uniformity, "we don't want to proceed." A hearing to question scientists is contemplated.

The bill's principal opponent is Cary Fowler, an agricultural researcher with the National Sharecroppers Fund in Wadesboro, N.C. "There are moral and ethical questions about patenting forms of life-like seeds," he said. "This law threatens the very existence of our major food crops."

Scientists are concerned that plant-breeding programs have led to the replacement of a multitude of traditional crop varieties with a few high-yield brands. Farmers worldwide have abandoned crop varieties which had evolved over thousands of years. The varieties are dying out, and with them a genetic heritage that will be needed for future research.

In 1970, one-fifth of the U.S. corn crop was destroyed by a blight that the National Academy of Sciences later blamed on farmers who were planting fewer types of corn and ones which shared the same genetic characteristics.

Only by returning to older varieties and isolating certain disease-resistant genes is agriculture able to combat new threats. As traditional varieties disappear through lack of use, "the problem of supplying enough food worldwide is clearly before us," wrote biologist Garrison Wilkes, in a 1977 Bulletin of the Atomic Scientists.

"The extinction of these local land forms and primitive races by the introduction of improved varieties is analogous to taking stones from the foundation to repair the roof," Wilkes wrote.

The National Academy of Sciences has reported " . . . most crops are impressively uniform genetically and impressively vulnerable. This uniformity derives from powerful economic and legislative forces."

A primary force, Fowler argues, is the palnt-patenting legislation that began in Europe in the 1960s, when French rose breeders pressed for protection. The laws were so difficult to enforce -- judges couldn't tell one tomato from its close cousin -- that European nations developed a list of legal and illegal varieties, he said. Thousands of common vegetable types have been banned under the system and farmers can be fined up to $800 in Britian for growing an outlawed variety.

Harold Loden, head of the seed trade association, said the European banning of illegal vegetables has nothing to do with the patent laws. "In Europe, there is a philosophy that the government looks after the farmer and tells him what he can plant. In America, we don't agree with that."

Genetic uniformity, he said, is "a fact of life when farmers plant the best seeds, because when they do, they end up planting the same thing."

Beyond the scientific implications, Fowler argues that the patent laws, by granting monopolies, allow companies to artificially boost prices. Also, he said, smaller seed companies unable to market the new varieties would be gobbled up by larger outfits a trend already visible.

"We are quite concerned over the implications of seed company takeovers by the petrochemical industry -- the manufacturers of pesticides and fertilizers," Fowler said, citing Upjohn, Union Carbide, Monsanto, Diamond Shamrock, ITT and Sandoz -- all seed company owners.

"At FMC, the seed business falls under the management of the Agricultural Chemical Group. The seed department manager is a former Agricultural Chemical Group planner. Are such practices creating a bias towards development of new varieties that are more needful of [pesticides and fertilizers]?" Fowler asks.

Loden sees nothing sinister in the trend. "There's concentration in the newspaper business, too," he said. "The same forces that affect other businesses affect us. Companies like to grow to make money to satisfy stockholders."

Whatever the outcome of this clash between the laws of nature and the laws of business, a House staffer confided he is "saddened and disappointed" by the controversy. "This is America," he assured a questioner. "We're not trying to sneak something over on anyone."