Papayas are Hawaii's second largest crop but are subject to infection by the ring spot virus. When this virus appeared on the island with the most papaya farms, nothing would control it and plants infected simply died.
At first, the problem was confined to the one island, so growers responded by raising papayas on another Hawaiian island. But the ring spot virus appeared there as well. Soon all the Hawaiian islands were affected. Agronomists expected the Hawaiian papaya industry to disappear completely in a short time.
Salvation came from Cornell University genetic engineers Dennis and Carol Gonsalves. They copied the gene for the ring spot virus' coat protein into the genome of a papaya. Coat protein, without the accompanying virus DNA, is harmless, but the modified papayas produce the coat protein and the plant's own immune system becomes primed to fight it. It's the same idea as we humans use to protect ourselves by vaccination. Drs. Gonsalves' transgenic papayas have thrived and are now the large majority of papayas grown in Hawaii.
Now, because most of the islands' papaya plants are virus resistant, there are fewer viruses around. This has made it possible to again grow traditional papaya varieties, whose fruit can be exported to Japan. The Japanese have not yet allowed the import of transgenic papayas.