Genetic engineering is already playing a role in protecting plants from disease, and the potential in this area is tremendous. The use of genetic engineering has the potential to help protect plants where other solutions are either impractical or ineffective. Also, the use of insecticides to control insects that are vectors for the transmission of diseases can be dramatically reduced, saving farmers time and money and protecting the environment from chemical sprays.
A few examples:
- The Rainbow and Sunup papayas from Hawaii were genetically engineered to protect them from the papaya ringspot virus (PRSV) which was devastating the crop. Summer squash were also engineered to protect them from several types of viral diseases. Papayas and squash are on the market now. Squash has been on the market since 1994 and has been of great value to squash growers.
- The U.S. citrus industry currently faces “citrus greening,” a disease that causes oranges to turn green and fall off the tree. The National Academy of Sciences has warned that citrus greening threatens the very existence of the U.S. citrus industry. Researchers are developing orange trees that incorporate genes from spinach that give them some resistance to the disease. If successful, the trees could save the industry.
- Plum trees and other stone-fruit trees are threatened by a deadly disease: plum pox virus (PPV). Scientists have developed a GM plum tree that is genetically resistant to the virus. As Cornell University puts it, “The most promising prospect for PPV resistance is genetic engineering.” The virus-resistant trees could protect stone-fruit orchards from incursions of the disease and protect nurseries from harboring the disease.
- The wine industry is threatened by Pierce's disease, which is caused by a pathogen carried by a sharpshooter insect. Currently, the only control for this disease is aerial spraying of malathion to kill the vector, which is not only undesirable but largely ineffective. The Davis technology, a gene fusion that delivers a one-two punch to the microbe, is a robust, sustainable method that introduces resistance into the vine itself so that it is impervious to the vector and pathogen. This not only saves millions in prevention and control costs but could potentially rescue the industry as a whole.
- Late potato blight is one of the most devastating plant diseases. It is caused by the oomycete Phytophtera infestans, a pathogen of the potato and, to a lesser degree, the tomato. It is a $5 billion problem and was responsible for the Irish potato famine. It requires heavy applications of fungicides to control — no potato has been bred to date that has any measure of resistance to the pathogen. A resistant potato named Fortuna has been developed that contains two genes from a wild-potato relative that confer robust resistance against disease, obviating the need to spray with fungicides.