University of Florida researchers have come up with a “promising” — albeit somewhat far off — solution to the citrus greening crisis that has threatened the state’s citrus industry for the past 20 years.
Scientists have developed a genetically edited tree that kills baby Asian citrus psyllids, the vector that transmits citrus greening disease, also known as huanglongbing or HLB.
The disease destroys or inhibits the development of every kind of citrus grown in Florida, said Lukasz Stelinski, an entomology professor at the University of Florida Institute for Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
The new approach involves inserting into citrus trees a gene that produces a protein that can kill baby psyllids.
“It prevents the vector population from developing on the plant,” Stelinski said. “They can’t form another generation.”
So far, the trees only have been tested in greenhouses and in the university labs, but plans call for expanding into field testing at the university within a year. There are no plans yet to conduct testing in commercial citrus groves.
Symptoms of citrus greening include small, lopsided fruit that doesn’t color, leaves with a light-greenish mottle and eventually a loss of foliage, fruit drop and reduction of fruit production as the health of the tree declines.
It can take several years for HLB to kill a tree. Sometimes, after greening weakens a tree, other factors, like invasive pests or the deleterious effects of a hurricane can “put the final nail in the coffin,” Stelinski said.
“The tree can succumb to the disease or to other secondary infections because the tree is so weakened,” he said.
While the new trees that researchers are developing might be effective in killing off baby psyllids, the adult psyllids would still exist, Stelinski said.
The ideal solution would be to combine the vector-resistant tree with a tree that also has some pathogen resistance, he said.
“We’ve inserted a gene into the citrus genome that makes it psyllid resistant,” Stelinski said. “You could stack that with another gene that makes it pathogen resistant.
“When we do both, it would be a done deal,” he added.
HLB is widespread in the Sunshine State.
“All uncovered trees in Florida are infected,” he said.
Replacing the state’s citrus trees will not take place overnight. Stelinski estimated that if the new trees are proven to be effective within five years, it could take decades to replace Florida’s millions of citrus trees.
“For this generation of growers, it’s too little too late,” he said.
But researchers aren’t limiting their research to the vector-resistant trees.
Thanks in large part to USDA funding, projects also are ongoing involving procedures like introducing antibiotics and installing improved physical barriers to keep psyllids at bay.
“The idea is to protect the current inventory so growers can stay in business while we release these new trees,” Stelinski said.
