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USDA-UCB team works to save citrus from elusive pathology

Research by three plant pathologists at the University of California-Berkeley (UCB) and United States Department of Agriculture (USDA) will help boost immunity in citrus plants and protect the valuable fruit against citrus greening.

Citrus greening, also called Huanglongbing (HLB) or yellow dragon disease, is a bacterial infection that is devastating the citrus industry. Infected trees produce fruits that are green, misshapen and bitter, unsuitable for sale as fresh fruit or for juice. Most infected trees die within a few years. Florida alone has experienced a 50% to 75% reduction in citrus production as a result. There are no resistant varieties of citrus available and limited disease control measures.

Because the bacteria that causes citrus greening cannot be grown in a lab, scientists have to find novel ways to conduct experiments. The UCB/USDA team looked at many different strains of the bacteria that cause citrus greening to see if they could identify peptides (a compound of two or more amino acids) that would trigger immune responses.

"This was a long list, so we narrowed it down by selecting small peptides that were a bit different in their peptide sequence, which might imply that the bacterium had made those sequence changes so that they wouldn't be recognized by the plant immune system," explained Jennifer D. Lewis, group leader of the research team. "Then we further narrowed that list to peptides from strains that caused disease in citrus."

Through this research, they showed that two peptides could trigger immune responses in multiple plant species, including citrus. These peptides may play a role in preventing or reducing yield loss from citrus greening.

According to Lewis, "We thought it was particularly interesting that some of the peptides predicted to elicit a response, could actually trigger immune responses in multiple plant species. This suggests that the immune response to these peptides is conserved across species."

The work was conducted at the Lewis Lab, located at the Plant Gene Expression Center in Albany, California. It is part of a unique collaboration between the Agricultural Research Service of the USDA and the Plant and Microbial Biology Department at UCB.

Read more about the research: https://phys.org/news/2020-03-technique-potential-oranges-citrus-greenin...

Read more about citrus greening from the USDA: https://www.aphis.usda.gov/aphis/resources/pests-diseases/hungry-pests/t...

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