How are herbicide resistant crops developed?
Researchers have used a variety of methods to discover and develop herbicides and the crops that can resist them. They began, in the 1940’s, by identifying synthetic chemicals that controlled weeds but did not harm crops. Virtually all crop plants have some endogenous resistance to the toxic effect of certain chemicals, because different plant groups, such as monocots and dicots, have significant biochemical differences. Organic chemists generated hundreds of molecules, sprayed them on weeds, and retained those that suppressed weeds. They then tested the herbicidal chemicals on crops. Promising candidates were subjected to a variety of tests required for regulatory approval: toxicity to various animals, environmental fate, environmental metabolism and agronomic performance. This method led to the discovery, regulatory approval and registration by the U.S. Environmental Protection Agency of over 100 herbicides. In the early days of herbicide discovery and development, researchers discar
