Can Genetically Modifying an Orange With a Spinach Gene Save Florida’s Crop?

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Tomorrow’s oranges might just have a little spinach in them. To battle the spread of a disease called citrus greening—which starves trees of nutrients and causes oranges to become green, misshapen, and bitter, and to fall prematurely—Tropicana supplier Southern Gardens Citrus has been funding research to engineer an orange plant that resists greening through a spinach gene. Field trials are “showing promise,” according to a recent update from Food Safety News.

The Department of Agriculture last week said orange output in Florida for the 12 months that started Oct. 1 will be 121 million boxes, the lowest since 1990, reported Bloomberg News. The decrease pushed up orange juice futures prices in New York.

Citrus greening, a disease spread by a small insect called a psyllid, has plagued Florida’s crop for about a decade and now threatens other citrus fruits such as oranges, lemons, and grapefruits in South Carolina, Georgia, Louisiana, Texas, and California. Greening has already cost Florida more than $4 billion in lost economic output and thousands of jobs since 2005, economists at the University of Florida estimate.

Having achieved little success with a search for an immune tree, unleashing psyllid predators like wasps and spraying large amounts of pesticides, growers are increasingly seeking a cure by engineering new, disease-resistant trees.

The spinach gene produces a protein that attacks the bacteria, according to Erik Mirkov, a Texas A&M University plant pathologist who’s leading the study. And no, it does not make the oranges taste like spinach.
Mirkov has grafted shoots of the new variety onto existing trees to help them flower faster, thus hastening safety testing of the new pollen on animals including bees and mice and, eventually, government testing of the juice. His work is described in a July New York Times story:

“In some rows were the trees with no new gene in them, sick with greening. In others were the 300 juvenile trees with spinach genes, all healthy. In the middle were the trees that carried his immediate hopes: 15 mature Hamlins and Valencias, seven feet tall, onto which had been grafted shoots of Dr. Mirkov’s spinach gene trees.”

While Southern Gardens’ testing has been positive, any juice from these trees remains years away. And their success on the market would be challenged by consumer concerns about the effect of genetically modified foods on health (such as provoking allergies) and the environment (like escaping into the wild or harming beneficial insects). As Southern Gardens President Ricke Kress told Food safety News: “Proof of success will only come with the public.”