field of genes


The good, the bad and the bleached: These varieties of corn resulted from conventional plant breeding.
Photos © David Tenenbaum

  The pause that defines
Before we explore the transgenic revolution in agriculture, let's get some quickie background info. Genetic engineering is the deliberate transfer of single genes between organisms. Genes are the stretches of DNA -- or occasionally RNA -- that carry information about the structure and function of all organisms.

field of genes

In a sense, farmers began primitive genetic engineering at the dawn of agriculture, when they kept seeds from their best plants, gradually improving the quality of successive generations. That practice accelerated early in the 20th century, when scientific plant breeders started using the principles of genetics to make plants with disease resistance, better structure or appearance, and higher yields.

Although plant breeders drastically increased crop yields, the technique takes many years, and it can only transfer genes between closely related organisms that breed with each other.

Those limitations are meaningless to genetic engineers who can accomplish in a few generations what once took dozens. Genetic engineers can also move traits between humans, bacteria and plants as easily as between members of the same species. In fact, the seeds being planted this year acquired resistance to insects or herbicides from bacterial genes.

Presto-Chango!
To make a long process short, genetic engineers isolate the gene they want and shoot it into a cell of the plant they want to transform. Then they grow that cell into a mature plant. If everything goes right, the offspring of that plant will contain the new gene. With correct breeding, so will all successive generations.

The technique has advanced rapidly since petunias and tobacco became the first transgenic plants in 1983. Potatoes and soybeans were genetically engineered in 1987 and corn in 1990. Since 1987, 48 genetically engineered crops have been field tested in the United States. Most of those were major crops like corn, but transgenic barley, broccoli, carrot, chicory, cranberry, eggplant, gladiolus, grape, pea, pepper, raspberry, strawberry, sugarcane, sweet potato, watermelon, and wheat have recently entered field testing, according to a U.S. Department of Agriculture fact sheet.

With the entire biosphere as a source of genes, genetic engineers have dreamed up plenty of ways to improve plants. Some want to increase resistance to stresses such as cold, heat, salinity or drought. Earlier this month (April, 1998), a group of scientists at Michigan State University announced that they'd genetically engineered a plant to overproduce a protein that sparks a defensive reaction to cold temperatures (see "Transferred Gene Helps Plants Weather Cold Snaps" in the bibliography). Genetic engineering can also make plants more valuable by forcing them to make nutrients they presently lack. And it could create plants that make drugs that would be expensive to manufacture.

I drink herbicides for breakfast...
Despite this wealth of prospects, two traits account for the bulk of commercial transgenic seeds:

  1. Insect resistance makes plants poisonous to insects.
  2. Herbicide resistance allows farmers to zap their fields with powerful herbicides that kill everything except the protected crops.

The genetic engineering companies proudly contend their new seeds have environmental benefits. As Rob Horsch, a Monsanto scientist, said in 1996, "By placing herbicide resistance inside plants, you won't need a season-long herbicide ... and you only spray where there's a weed problem." At the time, Horsch was director of transformation at the St. Louis agricultural biotechnology giant.

In the past few years, Monsanto has shed some chemical businesses and begun focusing on biotechnology, buying Calgene, Agracetus and other biotech firms. It's no accident that Monsanto is breeding seeds with resistance to Roundup. This best-selling, patented herbicide kills virtually every plant that hasn't received the resistance gene. Amongst herbicides, Roundup has a rather benign environmental record.

Resisting Roundup resistance
Nevertheless, Roundup resistance, which is incorporated in soybean seeds Monsanto says will be planted on 25 million acres in the United States, has sparked charges that transgenics are just a ploy to move weed killer. Greenpeace has even labeled Monsanto a "corporate criminal" for pushing a line of seeds that induce farmers to use more herbicide.

Monsanto CEO Robert Shapiro counters that herbicide and insect resistance are actually steps toward sustainable development. In 1995, he called biotech an essential tool in feeding the world's soaring population. "The simple arithmetic is that we're going to double the population, and we're not going to increase the amount of land under cultivation." Faced with an increasing army of the hungry, he said, we need creative -- and high-tech -- responses: "You have to get two times as much production from every acre of land than you get today... and you have to figure out how to do it sustainably."

Shapiro might be right. But then again, the pace of change in adopting genetically engineered crops is unsettling. Here's one question that's been bugging us.

Will insect-resistant crops hasten the evolution of pesticide-resistant insects?


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