One of the most important developments in agricultural technology in recent years has been the creation of genetically modified (GM) crops, which produce higher yields and are more disease-and pest-resistant than natural plant varieties. Although the advantages of such crops are obvious, they have aroused opposition from environmentalists. They fear that such disease-resistant “Frankenfoods” could damage the ecosystem by spreading their genes to ether plant species, with unknown consequences. What if, for example, an obnoxious weed developed the insect-fighting traits of a GM wheat plant? Even if the results did not directly affect humans, they would likely be catastrophic for plant diversity because the weed could spread rapidly, crowding out other species.   One possible answer to this fear is the “Terminator gene,” developed in 1998 by the U.S. Department of Agriculture (USDA) and Mississippi's Delta and Pine Land Company. This gene enables GM seeds to grew into edible plants, yet makes their offspring sterile, limiting the plants' growth to one generation. The use of such a gene, its developers argue, removes any danger of the contamination of natural plants by the new varieties.   Even if this is true, however, the real attraction of the terminator gene for biotech companies lies in their ability to protect intellectual property rights. This is because terminator technology (officially known as Technology Protection Systems, or TPS) would prevent the farmers who buy the seeds from producing second-generation seeds themselves. Thus TPS technology guarantees repeat sales for seed companies that have invested millions of dollars in the development of new strains of pest- and herbicide-resistant crops. Perhaps smelling the potential profits, biotech giants have already inundated the U.S. patent office with applications for terminator-gene seed strains.   Terminator seeds function as normal seeds until they are treated with a chemical known as an “inducer,” usually the antibiotic tetracycline. The inducer allows the terminator seed to flourish when planted, but prevents it from producing seeds that can be cultivated. A seed producer can stockpile as many fertile terminator seeds as it wants before they are treated and sent to market. “The whole system is designed to be a dead end,” says Melvin Oliver, the USDA plant biologist who spcarheaded the gene's development. “The seed goes nowhere.”   Detractors say that a large-scale shift to terminator-gene seeds would force subsistence farmers in the developing world to buy new seeds from seed suppliers each planting season, rather than rely on those from last year's yield. And history shows that once a new, advanced strain gains dominance in the market, there may be no turning back. Pat Mooney, executive director of a Canadian advocacy organization, says that poor farmers will have to climb on the terminator-seed platform or stay on the sidelines with old technology and hope they survive with outdated, inferior quality seeds. And even if the purchase of terminator seeds was subsidized by developed countries, Mooney says, farmers would then also be dependent on this aid, If the aid ever dried up, terminator companies could back out, leaving farmers with no grain,