The Hawaiian papaya industry in the mid-1990s looked as though it might be doomed. The papaya ringspot virus (PRSV) had devastated much of the island state’s production of the tropical fruit, causing output in the Puna district—the main production area, located on the main island of Hawaii—to plummet from around 55 million pounds (27,500 metric tons) in 1992 to almost half just six years later.
PRSV is a pathogenic plant virus that is found in most of the world’s papaya-growing areas. Spread by a small aphid, it severely reduces production, killing young plants, effectively resulting in a slow death of the crop. In Hawaii, where papaya is one of the major agricultural crops, along with sugarcane, pineapples, macadamia nuts and coffee, the impact was catastrophic. Farmers found themselves helpless as their papaya orchards withered.
Despite efforts to control the virus using traditional methods, these measures failed to slow the virus’s spread, as it continued to ravage both backyard trees and commercial orchards. Insecticides failed to stop it from spreading, and the only known remedy was to move to virus-free areas, but even this was only a temporary solution. In fact, the virus had first reached Hawaii in the 1940s, eventually causing the industry to move most of its production sites from the island of Oahu to Puna in the 1960s.
However, by the mid-1990s, the outlook was bleak, with family farmers’ livelihoods being destroyed. It became clear that a more permanent solution was needed to save the Hawaiian papaya industry. Biotechnology, along with the groundbreaking innovation of genetically modified (GM) papaya varieties, particularly Rainbow and SunUp, soon emerged as a light at the end of the tunnel, changing the trajectory of papaya farming in Hawaii.
The Birth of GM Papaya
Scientists from Cornell University, the University of Hawaii, The Upjohn Company and USDA’s Agricultural Research Service worked together to use biotechnology to develop a PRSV-resistant papaya. A leading figure in the efforts—and one of the first people to conceive the concept of genetically engineering a papaya to resist the virus—was Dr. Dennis Gonsalves, a Hawaiian-born plant pathologist and now-retired professor emeritus of plant pathology at Cornell.
By 1985, when the University of Hawaii began funding research into a GM variety of papaya, Gonsalves had already recognized biotechnology as a potential solution. Rapid scientific advances in the field during the preceding years made it possible to sequence and isolate plant genes, paving the way for this research.
The science behind the GM papaya is deceptively simple but powerful. The process essentially involved inserting a small piece of the virus into the papaya’s DNA, thereby triggering the plant’s immune response to the virus. “The idea was to try to make virus-resistant papaya, and the concept essentially was like vaccination,” explained Gonsalves in a 2016 video by Cornell University’s global communications initiative: Alliance for Science. By introducing a small fragment of the virus into the papaya’s genome, the plant would be able to build its own defense against PRSV.
At Cornell University, thousands of miles from the papaya farms of Hawaii, Gonsalves cultivated papaya seedlings in a greenhouse, experimenting with six or seven lines of transgenic plants. It wasn’t until later, after inoculating the plants with the virus, that it became apparent that the GM papayas were, in fact, resistant.
“Every day I would go and nothing would be happening, and then usually in about ten days the control plants started to get symptoms (of the virus), but this one transgenic one looked pretty good. Three weeks later—and this papaya kept on growing,” he said.
This breakthrough came as a beacon of hope for farmers who were facing the imminent collapse of their livelihoods. However, even with a scientifically sound solution, the GM papayas had to navigate regulatory hurdles before they could be planted on a commercial scale.
Approval from regulatory bodies such as the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA) was necessary to ensure that the GM papayas were safe for both the environment and consumers. Fortunately, by 1998, after years of testing and navigating red tape, the Rainbow and SunUp papaya varieties were given the green light, receiving food and environmental safety approval.
That same year, in a historic May Day celebration at the Hilo Hawaiian Hotel, the first genetically modified papaya seeds were distributed by lottery free of charge to local farmers. This marked the beginning of a new era for Hawaii’s papaya industry. This moment was particularly poignant because, by that time, nearly half of the papaya production in Hawaii had already been decimated by PRSV.
The adoption of Rainbow and SunUp varieties in the Puna district was swift. Farmers, who had once been on the verge of losing everything, began replanting their fields with the new GM papaya seedlings. Within a few years, the papaya industry began to rebound.
By 2010, Japan—one of the largest international markets for Hawaiian papayas, to which annual sales of Hawaiian papayas had peaked at $15 million in 1996, according to the USDA—approved the import of GM papayas, further solidifying the crop’s success.
“Technically it was quite simple, but I think the difference with our team is that it was in our hearts to try to solve the problem,” said Gonsalves.
Economic and Cultural Impacts
The revival of the papaya industry had far-reaching effects, not only on the economy but also on the cultural fabric of Hawaii. Papayas, which are rich in vitamins A, C, and E, are a staple in the local diet and play a significant role in Hawaiian agriculture. The papaya industry, which had once been nearly halved, was able to return to its former prominence, producing many millions of pounds of fruit each year. The GM papaya varieties ensured that family farms could survive, and in some cases, thrive.
For small-scale farmers like Ken Kamiya, who had been cutting down papaya trees infected by PRSV on a weekly basis, the introduction of GM papayas was nothing short of a miracle. In his words, the Rainbow papayas allowed his family to stay in business and provide for his children’s education. This sentiment was echoed by other farmers who had faced the tough decision of whether to continue farming or abandon their fields entirely.
The Anti-GMO Backlash
Despite the undeniable success of the GM papayas, Hawaii’s agricultural sector soon found itself at the center of a larger, global debate on GMOs and the role of multinational seed companies like Monsanto, Syngenta, and Pioneer Hi-Bred—many of which had a significant presence on Hawaii due to its warm year-round climate that allows for multiple harvests in one year and consequently the rapid development of new varieties.
Anti-GMO activists, bolstered by mainland organizations, began to target the papaya industry with claims that GM crops were harmful to the environment and human health. But as proponents of the GM papaya noted at the time, the transgenic variety only had the addition of a fragment of the PRSV, and Hawaiian consumers had been safely eating PRSV-infected papayas for decades.
Nevertheless, fields of GM papaya were destroyed by vandals, and there were efforts to introduce legislation to ban GM crops on several Hawaiian islands. This backlash created a polarizing atmosphere in Hawaii, where traditional farming methods and modern biotechnology seemed to be at odds.
The GMO debate became a deeply political issue, with local farmers caught in the crossfire. Many of these farmers, such as Yoni Kamiya, Ken’s daughter, were forced to defend their use of GM crops, emphasizing that their livelihoods depended on biotechnology.
The Future of Hawaiian Papaya
While the controversy surrounding GMOs in Hawaii persists, the success of the Rainbow and SunUp varieties has proven the potential of biotechnology to address agricultural challenges. The story of the GM papaya has become a major example of the power of science to solve real-world problems. And, as Gonsalves said: “One thing about the papaya story is it’s a story about the scientists being proactive.” Today, papaya farming continues to be a vital part of Hawaii’s agricultural landscape, thanks in large measure to the work of scientists like Gonsalves and the resilience of local farmers.
Looking ahead, the lessons learned from the GM papaya saga may serve as a blueprint for future biotechnological solutions, not just in Hawaii but around the world. Whether it’s combating citrus diseases or banana viruses, biotechnology holds the key to addressing some of the most pressing agricultural challenges of our time.