ARS | Publication request: Low incidence of Candidatus Liberibacter asiaticus in Diaphorina citri and its host plant Murraya paniculata

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 2011
Publication Date: June 1, 2012
Citation: Walter, A.J., Hall, D.G., Duan, Y. 2012. Low incidence of Candidatus Liberibacter asiaticus in Diaphorina citri and its host plant Murraya paniculata. Plant Disease. 96:827-832.

Interpretive Summary: Huanglongbing is a serious disease that threatens citrus production worldwide. In the United States (Florida), the disease is associated with the bacterium Candidatus Liberibacter asiaticus and spread by the psyllid Diaphorina citri. Both the psyllid and the bacterium have host plants other than commercial citrus, so non-crop plants may affect disease dynamics within a region. Murraya paniculata, or orange jasmine, is a common landscape plant that can be a host for both the psyllid and the bacteria. A one-year survey was conducted in which we monitored eight plantings of orange jasmine and adult psyllids that developed as nymphs on these plants for infection by Ca. L. asiaticus. Extremely low rates of infection by Ca. L. asiaticus were found in both psyllids and orange jasmine. Our results indicate that orange jasmine hedges may be a minor source of huanglongbing inoculum for nearby citrus groves.

Technical Abstract: Huanglongbing (HLB) is one of the most devastating diseases of citrus worldwide. Candidatus Liberibacter asiaticus is the prevalent species of three HLB-associated Liberibacter species, which is vectored by the psyllid Diaphorina citri. The vector and the bacteria have host plants outside Citrus, and these plants have the potential to affect disease epidemiology within citrus groves. Murraya paniculata could be especially problematic because it is a popular ornamental plant and a host of both psyllid and bacteria. We conducted a year-long survey of eight urban plantings of M. paniculata in east central Florida to characterize Ca. L. asiaticus infection rates in plants and associated psyllids. Using sensitive quantitative real time polymerase chain reaction (qPCR) primers targeting a prophage of Las, we found infection to be extremely low –less than one percent of psyllids and 1.8 percent of plants. With qPCR primers targeting Las 16S rDNA, none of the plants and only one psyllid were Las-positive. The titer of Ca. L. asiaticus is therefore low in M. paniculata and associated psyllids. These results suggest that urban plantings of M. paniculata are a minor source of Ca. L. asiaticus inoculum.