herbivores plant eaters il nematodes worms of the Nematoda phylum, many of which are parasitic pathogen disease-causing organism oooc ,oc plant breeder selection, rather than through genetic engineering. It is because of this natural resistance that has been bred into the crops that only 12 percent of the pesticides used in U.S. agriculture are fungicides.

Some viral resistance, however, has been bred into a number of crops through insertion of viral genes into the plant chromosomes. These genes may lead to the plant's producing viral proteins—biopesticides of a sort— that hamper a virus's own actions. This pathogen-derived resistance has been successfully used to protect Hawaii's papaya crop from the devastating papaya ringspot potyvirus. The viral gene was inserted into the papaya genome using a "gene gun," which shoots viral genes into papaya embryo cells.

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