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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Publications at this Location » Publication #318353
Title: Early detection of HLB with metabolomics

Author
item CHIN, ELIZABETH - University Of California
item LOBO, REBECCA - University Of California
item DA GRACA, JOHN - Texas A&M University
item Hilf, Mark
item McCollum, Thomas
item LEVESQUE, CYNTHIA - Citrus Research Board
item GODFREY, KRIS - University Of California
item SLUPSKY, CAROLYN - University Of California

Submitted to: Citrograph
Publication Type: Trade Journal
Publication Acceptance Date: 2/5/2015
Publication Date: 5/5/2015
Citation: Chin, E., Lobo, R., Da Graca, J., Hilf, M.E., McCollum, T.G., LeVesque, C., Godfrey, K., Slupsky, C. 2015. Early detection of HLB with metabolomics. Citrograph. 6:32-34.

Interpretive Summary: Huanglongbing (HLB) is the most devastating of all citrus diseases and poses a serious threat to the U.S. citrus industry. Candidatus Liberibacter asiaticus (CLas) is a bacterium associated with, and believed to cause, HLB disease of citrus. Confirmation of CLas infection is crucial for regulatory action and for management of HLB. Currently, CLas infection can only be confirmed by analysis of DNA extracts using polymerase chain reaction (PCR) to detect the presence of pathogen DNA. PCR-based detection of CLas DNA is extremely sensitive, however, in citrus trees that are infected with CLas, but not yet HLB-symptomatic, it is difficult to confirm the presence of CLas because the pathogen is not typically distributed evenly throughout the tree making selection of appropriate samples challenging. Inability to detect CLas in infected, but asymptomatic trees means that trees may be clandestinely serving as a source of inoculum for non-infected trees. An alternative to confirmation of infection by direct detection of CLas DNA by PCR is to measure pathogen induced changes in citrus that are indicative of infection. Initiation of the plant’s defense system leads to a cascade of changes in metabolic pathways to create signal molecules, enzymes, proteins and other biochemical machinery. These changes occur soon after infection, and measuring the changes in quantity of the participating metabolites can identify the metabolic pathways that shift in the plant. In this project, Nuclear Magnetic Resonance (NMR) is being utilized to identify changes in metabolites that are indicative of CLas infection prior to the appearance of HLB symptoms. Results consistently show that there is a CLas specific metabolite fingerprint that may be used for detection of CLas in citrus. Improvements for detecting CLas infection are essential to combating the spread of HLB. Early detection of HLB allows for earlier intervention (tree removal and, perhaps eventually, treatment of the diseased tree), which will play a key role in preserving the citrus industry. Metabolomics offers a promising new strategy for the early detection of, defense against and resolution of HLB in the United States and the survival of the citrus industry.

Technical Abstract: Huanglongbing (HLB) is the most devastating of all citrus diseases and poses a serious threat to the U.S. citrus industry. Candidatus Liberibacter asiaticus (CLas) is a bacterium associated with, and believed to cause, HLB disease of citrus. Confirmation of CLas infection is crucial for regulatory action and for management of HLB. Currently, CLas infection can only be confirmed by analysis of DNA extracts using polymerase chain reaction (PCR) to detect the presence of pathogen DNA. PCR-based detection of CLas DNA is extremely sensitive, however, in citrus trees that are infected with CLas, but not yet HLB-symptomatic, it is difficult to confirm the presence of CLas because the pathogen is not typically distributed evenly throughout the tree making selection of appropriate samples challenging. Inability to detect CLas in infected, but asymptomatic trees means that trees may be clandestinely serving as a source of inoculum for non-infected trees. An alternative to confirmation of infection by direct detection of CLas DNA by PCR is to measure pathogen induced changes in citrus that are indicative of infection. Initiation of the plant’s defense system leads to a cascade of changes in metabolic pathways to create signal molecules, enzymes, proteins and other biochemical machinery. These changes occur soon after infection, and measuring the changes in quantity of the participating metabolites can identify the metabolic pathways that shift in the plant. In this project, Nuclear Magnetic Resonance (NMR) is being utilized to identify changes in metabolites that are indicative of CLas infection prior to the appearance of HLB symptoms. Results consistently show that there is a CLas specific metabolite fingerprint that may be used for detection of CLas in citrus. Improvements for detecting CLas infection are essential to combating the spread of HLB. Early detection of HLB allows for earlier intervention (tree removal and, perhaps eventually, treatment of the diseased tree), which will play a key role in preserving the citrus industry. Metabolomics offers a promising new strategy for the early detection of, defense against and resolution of HLB in the United States and the survival of the citrus industry.