Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2011
Publication Date: June 1, 2011
Citation: Ammar, E., Shatters, R.G., Hall, D.G. 2011. Localization of Candidatus liberibacter asiaticus associated with huanglongbing in various organs of its pysllid vector using FISH and Q-PCR. Phytopathology. 101:56.
Candidatus Liberibacter asiaticus (Las) has been associated with huanglongbing (HLB), or citrus greening, which is currently the most devastating citrus disease in many areas of the world. HLB is transmitted in Florida by the Asian citrus psyllid Diaphorina citri (Hemiptera, Psyllidae) in a persistent manner, but its vector interactions with the vector, particularly at the organ and cellular levels, are poorly understood. We used fluorescent in situ hybridization (FISH) and quantitative PCR (Q-PCR) for the localization of Las in D. citri. Las was detected by FISH in the hemolymph, filter chamber, midgut and the salivary glands of D. citri collected from HLB-infected citrus trees, as well as in the phloem of infected citrus leaves. Additionally, Q-PCR detected Las in dissected organs of individual D. citri adults collected from HLB-infected citrus plants in the field or the laboratory. The proportion of infected (Las-positive) salivary glands (47-70 percent) was significantly lower than that in other body parts (79-98 percent). The relative titer of Las, compared to psyllid genomic DNA in each sample, was significantly higher in both the salivary gland and alimentary canal compared to that in the rest of the insect body. These results provide the first molecular localization of Las in the hemolymph, alimentary canal and salivary glands of D. citri. They also strongly suggest that the salivary glands constitute an important infection and/or transmission barrier to Las in the psyllid vector, and that Las may replicate or accumulate in both the alimentary canal and salivary glands of D. citri.