Breakthrough in Search for a Citrus Greening Cure

Published on September 16th 2019
Fruit growers may rejoice in the knowledge that an important step has been made towards finding a treatment for the devastating disease 'huanglongbing', or citrus greening. The invasive virus, spread by psyllid insects, is one of the biggest threats to the world's lemon, lime, orange and grapefruit trees.
A close up of a green apple
The disease, nicknamed 'yellow dragon' due to the distinct discolouration of its host's leaves, has no cure. Efforts have eluded the scientific community for decades due to the inability to create conditions for the microorganism, which causes citrus greening to grow inside a lab.
However, Stanford University researchers have now made a breakthrough by studying a distant relative of the damaging bacteria. It's resulted in a shortlist of 130 compounds that could be used in potential treatments of the citrus killer.
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Citrus greening harm

Originating in Asia, citrus greening has wreaked havoc on groves across countries like the US, China, Brazil, India and Paraguay. To convey is destructiveness, the disease is estimated to have shrunk US orange production by 72 per cent between 2007 and 2018.
Once in a plant, the bacterium's devastating effects cannot be stopped. Signs it is attacking your conservatory citrus plant or crop include leaf discolouration, misshapen fruit, as well as branch dieback and stunting. Currently, the most common treatment is prevention through spraying crops with antibiotics.

Stanford University research

A close up of food
The Stanford University study reveals the exploration of new treatment methods using a distant cousin - Sinorhizobium meliloti - of the citrus virus bacteria. The research, published in the Proceedings of the National Academy of Sciences journal, introduced genes from citrus greening into test Sinorhizobium meliloti cells. The bacteria were then engineered to glow green when citrus greening proteins were active.
It's a quirky development that has provided scientists with a visual aid or screen to gauge and determine when potential treatments have had a positive impact. According to the study, when a compound inhibited citrus greening proteins, the engineered cell dimmed less green. Through the process scientists found 130 out of 120,000 compounds lessened the impact of citrus greening without damaging growth, raising hopes that an outright cure may be found in the future.
"What we've completed is just a small part of what needs to be done," said Melanie Barnett, lead author of the paper. "It's beyond our expertise to pursue these findings to the level needed for real-world application, but it's a foot in the door for researchers who can take those next steps."
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