A Glimmer of Hope in Citrus Country

Ron English had spent 35 years as production manager at his family’s Florida citrus business when the state was hit by citrus greening, a disease that has ravaged Florida’s iconic orange and grapefruit industry.

Ron English, Valrico, Florida: “In 2015, we decided that greening had hurt us enough to where the quality of fruit wasn’t there. When it hit us, it hit us hard. It didn’t gradually go out. All that we did to try to - what we knew to do to to keep the trees alive - didn’t work. So we made a decision just to shut our operation down. … My father-in-law and our family had been in since 1895.”

Life-changing decisions like this one have become common across Florida since citrus greening, also referred to as HLB, emerged in 2005. Since that time, producers in the state have lost 63 percent of their citrus-bearing acres. While some owners of those 429,000 acres of former groves switched to other forms of agriculture or kept the land, many sold to developers.

Ron English, Valrico, Florida: “We were able to sell, something we didn’t want to do….Where we once had groves are subdivisions, strip centers, malls.”

Citrus greening, caused by a bacteria spread by the tiny, non-native Asian citrus psyllid, destroys orange, grapefruit, tangerine and other citrus trees.

English recently saw a 1950s ad showing children drinking Florida orange juice. It reminded him how long Americans have associated Florida with oranges. Now, the state’s orange production has plummeted 90 percent, from nearly 150 million 90-pound boxes in 2005 to 15.8 million boxes in 2023 - the lowest annual production since the 1930s.

But English has found himself back in an orange grove, feeling hopeful. He oversees a test grove for a company called Soilcea, which has licensed the rights to further develop and commercialize precision-bred citrus trees from the University of Florida. Plant biologist Nian Wang and university colleagues used CRISPR technology – a genome editing tool – to develop trees that can still survive and produce fruit despite exposure to the devastating bacteria. The trees contain no foreign DNA from other plants or animals. If successful, these genetically edited trees and root stock could revive citrus production in Florida, and save it elsewhere.

Nian Wang, professor of Microbiology and Cell Science, University of Florida: “This problem is not only a Florida problem. It’s a worldwide problem. In all the major citrus production areas, in Asia, in Brazil, in the United States. We all have the same problem.”

About 50 miles from Wang’s central Florida labs, Soilcea’s Tampa-area facility houses a dozen employees who are rapidly refining the most promising genetic edits. Early results have been positive, with the first priority on Valencia and Hamlin orange varieties and an edited root stock for grafting.

Yianni Lagos, CEO, Soilcea: “What we’re doing is finding the specific genes that are susceptible to HLB and using CRISP precision breeding to turn off this interaction. And this occurs all the time in nature, and then natural selection takes over and that becomes the dominant trait. We’re just using it to be very targeted to help speed up the recovery of the citrus industry…And we have a tree that we are saying is showing early HLB resistance. We hope it’s going to last for a lot longer but we only have trees that have been in the field a couple years…Every six months we retest them to see if the bacteria is growing in the tree and what’s going on. And every six months, we are getting more and more confident.” 

Lagos and his colleagues are also working on citrus greening-resistant grapefruit and mandarin oranges.

Quinton Allen, Senior Scientist, Soilcea: “We have to screen lots and lots of plants, and different combinations of different CRISPR edits to see what plant has the desired edit and which one has the desired traits of resistance that we are hoping for.…We spend a lot of time. These plants take six months to a year to get to the stage where they are in soil so we have to be very thorough in screening so all the effort we are devoting for this isn’t a waste.”

In the past decade, Floridians have tried one possible solution after another, from spraying to kill the insects to tenting the young trees to protect them. All either failed or required costly repeated treatments.

Yianni Lagos, CEO, Soilcea: “We do feel the pressure to get it to growers quickly because I mean they’re really struggling. It’s a real testament to the growers that they’ve stayed in this industry even with citrus greening.”

And now, they may be close.

Yianni Lagos, CEO, Soilcea: “How do you know they are disease resistant? Well you gotta put it into the field. You have to expose it to the psyllid, you have to expose it to the disease.”

So far, researchers say the trees that result from precision breeding look much healthier than the control trees.

Quinton Allen, Senior Scientist, Soilcea: “Different gene targets are showing tolerance where the plant actually still gets infected but it’s a big, beautiful tree compared to the controls. We are seeing others where the amount of bacteria in the plant is so low or almost undetectable compared to the controls.”

All that work in University of Florida and Soilcea labs and greenhouses may finally bear fruit. Literally, they hope. But it takes almost half a decade before citrus trees produce significant amounts of fruit, after which traits such as taste and yield will need to be evaluated.

Yianni Lagos, CEO, Soilcea: “If everything goes well, I think we would be looking at the end of 2026 or maybe the spring of 2027 when we get those first commercial trees out there…But they are still going to have plant these trees in numbers, and it’s going to take four, five years, even maybe a little longer, before it’s at full production. So to really start bringing the industry back, it’s going to take some time.” 

As for Ron English, he is once again optimistic that his grandchildren might someday have the opportunity to get the family back into the citrus business.

Ron English, Valrico, Florida: “This, what we’re doing, is the key to getting back. And once we can get people started and start planting, I think it will catch on.”

By Colleen Bradford Krantz, colleen.krantz@iowapbs.org