Title: The salivary gland and alimentary canal as transmission barriers to Candidatus Liberibacter asiaticus in the Asian citrus psyllid, vector of citrus huanglongbing diesease Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 4, 2011
Publication Date: N/A
Technical Abstract: Candidatus Liberibacter asiaticus (Las), associated with huanglongbing disease, is transmitted by the Asian citrus psyllid (ACP, Diaphorina citri) in a persistent manner. For a persistent pathogen to be transmitted, it has to be ingested, pass through the alimentary canal wall, move through hemolymph to the salivary glands, and pass into the salivary secretions, so that it can be inoculated into host plants during feeding. We used quantitative polymerase chain reaction (qPCR) and fluorescent in situ hybridization (FISH) for localization of Las in dissected organs of ACP that fed on Las-infected citrus. Las was detected in the alimentary canal, hemolymph, salivary glands, and other organs/tissues of ACP. The relative titer of Las compared to psyllid genomic DNA, using qPCR, was significantly higher in both the salivary gland and alimentary canal compared to that in other tissues, suggesting that Las may replicate or accumulate in both organs. Using FISH, the proportion of Las-infected salivary glands (21.2 percent) was significantly lower than that of infected alimentary canals (44.4 percent) or other organs/tissues (41.8 percent). Using qPCR in combination with a detached leaf assay method, only 4-5 percent of the psyllids were able to inoculate Las into detached citrus leaves, although 46-78 percent of these psyllids were Las-infected. Our results show the near systemic infection of ACP by Las and suggest that both the alimentary canal and salivary gland constitute infection and/or transmission barriers to Las in this vector. Further research on these transmission barriers, and possible receptors associated with them, can potentially help in devising innovative control methods aimed at blocking Las transmission by ACP.