Are the ripening fruits of genetic engineering bitter or sweet?

Altered Harvest: Agriculture, Genetics, and the Fate of the World's Food Supply, by Jack Doyle. New York: Viking Penguin Inc. 502 pp. paper, $8.95 One would think farmers had enough to worry about.

As politicians search for solutions to continuing farm problems, few realize that the key to farming's future lies not on the land, nor in the loan office, but at the bottom of a laboratory test-tube.

Genetic engineering - the manipulation of the complex biological makeup of crops, animals, and bacteria - is transforming the way food is produced. Possibilities include abundant crops immune to pests and frost, and bigger, healthier livestock.

Potentially, this ``biotechnology'' revolution could make all farmers prosperous and help feed the world's hungry. But it may more likely drive thousands more off the land, destabilize the entire food chain, and threaten the environment.

So argues Jack Doyle in his exhaustive and compelling analysis of our agricultural system. Based on three years of research, ``Altered Harvest'' was first published in 1985 and is now available in paperback.

According to Doyle, a researcher at the Washington, D.C.-based Environmental Policy Institute, genes have become central to food production: They determine the color and shape of a tomato, the hardiness and nutritive value of a wheat stalk, and the size and quality of a Holstein cow. In Doyle's view, whoever learns to manipulate those genes most effectively will control how farming is done.

Therein lies the danger. Knowledge of agricultural biotechnology is being concentrated into very few hands, Doyle warns. He describes how, since the early 1970s, there has been a ``coupling of genetic power with corporate power'' with big multinationals in the ``best position to win the agri-genetic sweepstakes.''

Genetic engineering will further skew farming's misplaced priorities, Doyle believes. Over the years, United States agriculture has come to equate productivity with total output - be it bushels of corn per acre or gallons of milk per cow. To stay in the game, farmers have doused their fields with chemical pesticides and fertilizers and invested in expensive farm equipment.

Along with a dependence on capital, the quest for high yield has led to less genetic variety in the crops and livestock farmers raise. This is understandable, since only the exclusive lines that provide the highest outputs are profitable. But, as Doyle's analysis of the 1970 corn blight shows, the few select genes that make a particular variety of corn produce a record crop can also make it more vulnerable.

Furthermore, with high yield still the name of the game, corporate-funded researchers can be expected to develop superproductive crop-lines and livestock breeds with increasingly narrow and vulnerable gene pools. Doyle feels that ``we may be moving toward a high-tech, house-of-cards agriculture worldwide, with genetic engineering at its base; a system in which one monkey wrench or one unforeseen mutation can create enormous problems.''

The most controversial issue in agricultural biotechnology concerns the release of genetically altered bacteria into the environment - bacteria that can, for example, prevent frost from forming on plant leaves. Critics charge that, once unleashed, such mass-produced microscopic mutants could alter the world's weather patterns, while proponents play down any threat. In a powerful chapter entitled ``Environmental Roulette,'' Doyle concludes that we simply know too little about the potential consequences to proceed sanguinely.

Doyle thoroughly examines what the biotech future of agriculture may hold for farmers, for consumers, and for the world economic and political orders. While he goes out of his way to sound optimistic notes, most of the evidence he has so painstakingly presented leads one to conclude that there is little to cheer about.