Characterization of Liberibacter populations and development of field detection system for citrus huanglongbing
A project funded by USDA NIFA
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Riverside labs (USDA and University of California Riverside) and Florida Division of Plant Industries (DPI) have found that psyllid testing can be used for early detection of HLB in orchards. CLas-positive psyllids can be found months to years before pathogen detection in plants (Manjunath et al. 2008). Psyllids and ornamental rutaceous plants facilitate long distance spread of the disease (Halbert et al. 2012).
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Citrus relatives showing severe HLB symptoms are negative for CLas suggesting presence of novel variant Liberibacter populations. In a recent study, the Riverside group has discovered a new fourth species of Liberibacter, tentatively named as 'Candidatus Liberibacter caribbeanus' (CLca) from both ACP and citrus samples in Colombia, S. America. These and other evidences show the necessity to test for possible variant Liberibacters in nature as well as the need to develop tools capable of universal detection of Liberibacters instead of currently used species specific detection.
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The Riverside labs, University of Hawaii (UH), and Diagenetix, Inc. (a biotech company located in HI), have developed a loop-mediated isothermal amplification-based field detection system (LAMP) using the Smart-DARTâ„¢ platform (Keremane et al., 2015). This methodology was demonstrated at several venues for scientists and growers; two workshops were conducted in October 2013 to train growers, nurserymen, and extension personnel in conducting field detection of CLas in psyllids.
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Texas A&M University and Riverside labs have found that the LAMP methodology is efficient in detecting CLas in root samples prior to the appearance of foliar symptoms.
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DPI and the University of Florida (UF) have developed 'SmartTrap' devices that trap psyllids with about the same efficiency as yellow sticky traps. Unlike yellow sticky traps that capture all insects, the SmartTraps selectively trap psyllids.
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DPI, the Diagnostic Laboratory of the US Sugar, Inc., Florida and Riverside labs have shown that a non-alcohol based preservative could be used for collection and storage of psyllids from traps. CLas was reliably detectable in psyllids stored in this preservative for several days under field conditions or at room temperature thus eliminating the risks and regulations associated with transportation of psyllids in alcohol preservatives.