The science of genetics has made astonishing progress in the last half of the 20th century. Geneticists have made remarkable gains in deciphering the genetic code that gives each species its particular traits. They have discovered methods of transplanting genetic material from one species to another, and have been able to transfer such genetic traits as disease resistance, time to maturity, or the yield that a plant produces.Unlike hybrids, genetically manipulated (GM) plants are not sterile, but some agribusiness firms have produced so-called "terminator" genes, which prevent a GM plant from germinating and reproducing. Another development is a plant that is resistant to a particular variety of herbicide. Both of these developments have been very controversial, provoking charges that they have been developed, not with the best interests of farmers in mind, but with the goal of selling more seeds and herbicides.
While early success has been considerable, there is widespread concern that we just don't know enough about the long-term consequences of genetic manipulation of crops and animals. For example, if the terminator genes from a GM wheat species were somehow to cross-pollinate with any number of wild plants around them, it could well mean the end of those wild varieties. Likewise, if the herbicide-resistance gene were to pollinate with a species of weed, the result might be to create a species of nearly indestructible superweed.