Alisa Gravitz, responding (letters, Feb. 4) to our " General Mills GIS +0.46% Has a Soggy Idea for Cheerios" (op-ed, Jan. 21), is wrong on every count. She claims that our op-ed "fails to explain the difference between hybridization and genetic modification," although its focus was on the relationship between older and newer techniques for genetic improvement. For decades plant breeders have had numerous tools, including irradiation or chemicals to mutate plants' DNA to create entirely new genetic sequences. And in wide-cross hybridizations, which are performed between organisms of different species or genera, the parental plants may not be sufficiently compatible to permit development of a mature plant, so scientists devised mechanical and biochemical ways to "rescue" the embryos and make them viable. Common, currently cultivated commercial crops derived from wide crosses include tomato, potato, sweet potato, oat, rice, wheat, corn and pumpkin, among others. These are distinct from the gene-splicing that Ms. Gravitz and other antibiotechnology activists oppose.
Also, it's not correct that "the most common form of genetic engineering is to insert a bacteria [sic] pesticide into the DNA of a plant"; far more common is the insertion of genes to confer resistance to herbicides, for improved, more environmentally benign weed control.
There is no evidence that a single ecosystem or human consumer has ever been harmed by a genetically engineered crop, but there are documented cases in which conventional breeding methods have resulted in plants with harmful levels of natural toxins, allergens or antinutrients, or greater susceptibility to disease.
Ms. Gravitz is exercised about the fact that as we consume some gene-spliced plants, we are "eating pesticides," but the vast majority of the pesticidal substances that humans eat occur "naturally" in our diets, whether in organic, conventional or genetically engineered foods. University of California biochemist Bruce Ames and his colleagues have found that "99.99% (by weight) of the pesticides in the American diet are chemicals that plants produce to defend themselves."