UC Davis Study Offers Hope to Stop Incurable Citrus Greening

While the devastating disease Huanglongbing (HLB), or citrus greening threatens to wipe out the citrus industry in the United States, a team of plant scientists in the University of California, Davis (UC Davis) and the U.S. Department of Agriculture worked on a research study that will offer new hope to treating the disease. HLB is caused by three species of the Candidatus Liberibacter bacteria, including Candidatus Liberibacter asiaticus, also known as CaLas. These bacteria are carried from tree to tree by two species of the citrus psyllid, a winged insect that attaches itself to the underside of the trees' leaves.

In their study, the researchers studied four categories of healthy and diseased citrus trees, to better understand how HLB affects trees during the very early stages of infection. Their analysis confirmed that in infected trees, HLB disease caused starch to accumulate in the leaves, blocking nutrient transport through the phloem and decreasing photosynthesis. They also found that normal metabolism of sucrose, a sugar also key to photosynthesis, was disrupted. The researchers also discovered that HLB interfered with the regulation of hormones such as salicylic acid, jasmonic acid, and ethylene, which are "the backbone" of plant immune response. They also found that infected trees had changes in the metabolism of important amino acids that serve as a reservoir for organic nitrogen required to stimulate plant immune response in many plants. The team anticipates that their discoveries will lead the way to new tests for detecting the bacteria and the presence of HLB in orchard trees. They also suggest that it may be possible to develop several short-term treatments for infected trees.

For more details about this research, read the news release available at http://news.ucdavis.edu/search/news_detail.lasso?id=10701.