Scientists at the University of Florida are conducting exciting research on a new type of citrus tree designed to combat the tiny insects responsible for citrus greening. 

While this genetically edited tree has only been tested in laboratory and greenhouse settings, it represents one of the most promising advancements to address a persistent challenge that has significantly impacted Florida's citrus industry over the past two decades.

The innovative approach involves inserting a gene from the soil-borne bacterium Bacillus thuringiensis (Bt) into the citrus tree. This gene instructs the plant to produce a protein capable of killing young Asian citrus psyllids, the insects that transmit the greening disease. 

Although this method effectively targets juvenile psyllids, researchers at UF/IFAS are also working on solutions to manage adult pests.

“We aim to implement a sustainable biotechnological solution that is easy for growers to adopt, reducing reliance on insecticide sprays,” explained Lukasz Stelinski, an entomology professor at the UF/IFAS Citrus Research and Education Center. “While our current Bt trees can eliminate juvenile psyllids, some degree of insecticide use may still be necessary for adult control.”

The next critical step is to validate its effectiveness in field conditions. Stelinski anticipated that testing will commence within a year, but it may take a few more years to establish comprehensive results.

Since the arrival of greening disease, also known as Huanglongbing (HLB), in Florida in 2005, it has severely harmed the citrus trees and their fruit, prompting ongoing research for sustainable solutions. The UF receives crucial funding from the U.S. Department of Agriculture to support citrus greening research, accelerating advancements in this area.

According to Stelinski, the modified tree's ability to kill all juvenile psyllids feeding on it is a significant defensive measure. 

“A citrus tree that produces its own strong defense against the Asian citrus psyllid by suppressing this insect's reproductive capabilities could potentially reduce or eliminate vector populations,” he noted. “This strategy could significantly hinder the spread of HLB by limiting the effectiveness of its main vector.”

Before this research initiative began, it was known that certain Bt proteins could eliminate other sap-sucking insects, but none were found to target Asian citrus psyllids specifically. The protein works by binding to specific receptors in the psyllid's gut, forming pores that disrupt gut cell function and lead to the insect's death. 

In their experiments, researchers at CREC successfully inserted a Bt gene into citrus trees, producing a protein within the phloem (the part of the leaf where psyllids feed). This protein ultimately protects the tree from infestation and, consequently, from citrus greening.

Bryony Bonning, a distinguished scholar and entomology professor at the main UF campus in Gainesville, led the research identifying the bacterial proteins effective against psyllids. The latest study reveals that the Bt-derived protein can eliminate the vast majority of psyllids during their early life stages, preventing new adults from emerging and thus disrupting their reproductive cycle.

While adult psyllids continue to pose a challenge, the current focus remains on controlling juvenile psyllid populations on citrus trees. 

“Given the successful application of Bt proteins in safeguarding other crops from insect pests, we believe we are making significant progress in controlling the Asian citrus psyllid,” Bonning stated. “The next step is to demonstrate this method's efficacy in real-world conditions so that citrus growers can effectively combat the insect that transmits this devastating disease.”

*Featured photo courtesy of UF/IFAS

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