A citrus disease might be cured by genetic modification. But would the public allow it?

By JR Williams

In 2005, orange groves across Florida began showing signs of a lethal disease called citrus greening. The disease chokes the fruit’s maturity process, leaving behind a perpetually half-developed orange. After a few years, greening kills the whole tree. Today, 90% of Florida orange groves are infected with greening, which carries a 90% mortality rate, and has no cure.

In an effort to fight the disease, researchers at Southern Gardens Citrus, an orange juice processor and supplier in Clewiston, Florida, are experimenting with genetic modification. By introducing spinach DNA into citrus DNA, they’ve seen young orange trees begin fighting off greening bacteria for the first time ever. Tim Eyrich, Vice President of Research and Commercialization at Southern Gardens, said that years of testing will be necessary to prove how effective the method will be.

He explained that GMO testing must be done during the process of blooming, and it can take four to eight years for a new tree to bloom.

“None of our trees have broken juvenility yet,” Eyrich said, “but we have found that with the spinach DNA, we can defend the plants in a unique way against the bacteria.” Researchers have seen the spinach protein produce positive activity against the greening bacteria, known as HLB, he said.

Until Southern Gardens finishes its research, farmers are trying to work around the disease. John Griffis, associate professor of Landscape and Horticulture at Florida Gulf Coast University, said there are ways to deter HLB, but they are painstaking.

“By micromanaging every plant carefully, we found that citrus trees can outlive the disease,” Griffis said. “By keeping the water and fertilizers at good levels, the plants can grow for several years, even if infected.”

A healthy orange tree can live and produce fruit for up to 30 years. An infected tree may live 15 to 20 years before succumbing to the terminal effects of the disease.

Greening spreads through the toxins of the Asian citrus psyllid, a type of plant lice. The citrus psyllid feeds off the edges of the orange leaves and spreads the disease from infected plants to healthy plants. Griffis said heavy use of pesticides is one way to combat greening. However, this is not always 100% effective and can be very expensive. It can also have environmental consequences.

“Aggressive assault against psyllids is effective,” Griffis said, “but there is a concern over the amount of toxic chemicals we would have to use to fight them off.”

Genetic modification can reduce the need for pesticides and herbicides and can produce a higher yield with more nutrients. It looks promising for combatting citrus greening. But it faces a barrier.

Most people are spooked by GMOs, according to Fritz Roka, Ph.D., an agricultural economics professor at FGCU. And this concerns scientists.

“There is a fear,” Roka said, “that even if we can cure citrus greening through transgenetics, people will be scared away from purchasing citrus because of the stigma of GMOs.”

Saving orange groves with GMO technology could mean destroying their economic value, Roka said. He offered genetically modified corn as an example.

“Roundup Ready corn uses fewer herbicides and pesticides to grow more fruit, but the fear of GMOs affects the economic value of it.”

Why does the public fear genetic modification of food?

“People don’t understand the science behind it,” said Elizabeth Malek, Ph.D., a crop health specialist at Lipman Family Farms, who works in Ruskin, Florida.

Malek said that the process of creating GMOs is essentially turning up a vitamin gene in the plant, or deleting certain genes in the genome. Plants can do this naturally, but it takes a long time to change an offspring’s genetics. By manipulating the natural rate of change, scientists can condense several generations’ worth of evolution into a few years. This rapid change causes distrust and fear in consumers, she said.

One misconception, she said, is that human genes can be altered when we consume GMOs.

“The DNA of tomatoes that we eat doesn’t come in contact with our DNA,” she said. “We digest what we need for cellular process, and we pass it.”

There’s consensus in the scientific community that GM foods are safe, according to a 2016 report from National Academies of Sciences, Engineering, and Medicine. Yet four in 10 Americans believe that GM foods are worse for their health than non-modified foods.

Modifying citrus DNA with spinach DNA could prove fruitful against citrus greening. Using this method, farmers might be able to fight off HLB without pesticides.

“For the first time, there are events taking place that look promising,” Eyrich said.

But Roka said that as long as the public’s fear exists, GMOs won’t be economically viable, despite their many benefits.

“Scientists can go off the rails, screaming about how safe it is, but it only matters what the buyers believe,” Roka said. “It’s the marketplace reality.”