Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/26/2007
Publication Date: 4/8/2008
Citation: Keremane, M.L., Halbert, S.E., Ramadugu, C., Webb, S., Lee, R.F. 2008. Detection of Candidatus Liberibacter asiaticus in Diaphorina citri and its importance in the management of Citrus Huanglongbing in Florida. Phytopathology, 98: 387-396 Interpretive Summary: Citrus huanglongbing (HLB or citrus greening) is a destructive disease of citrus now present in Florida and Brazil in the Western Hemisphere. Its psyllid vector, Diaphorina citri is present in Texas and Mexico thus threatening the future of citrus production elsewhere in North America if HLB should be introduced. We report the application of a Taqman based real-time quantitative PCR assay for the detection of HLB in psyllids and the development of a Taqman probe to monitor the quality of DNA extractions from the psyllids. The summary of results of the analyses of over 1200 samples of psyllid adults and nymphs collected from Florida are reported. The results show that HLB may be detected in psyllids in an area 1-2 years before the development of HLB symptoms and confirmation from plants, also the study suggests that garden stores and retail nurseries may have played a important role in the distribution of infected psyllids and plants.
Technical Abstract: Citrus huanglongbing (HLB or citrus greening) is a highly destructive disease that has been spreading in both Florida and Brazil. Its psyllid vector, Diaphorina citri, has spread to Texas and Mexico thus threatening the future of citrus production elsewhere in North America. Even though, sensitive diagnostic methods have been developed for detection of the causal organisms, Candidatus Liberibacter spp., the pathogen cannot be readily detected in plants until the symptoms develop, presumably because of low concentration and uneven distribution of the causal bacteria in non-symptomatic tissues. In the present study, Taqman based real-time quantitative PCR methodology was developed for detection of Ca. Liberibacter asiaticus in Diaphorina citri. Over 1200 samples of psyllid adults and nymphs, collected from various locations in Florida, from visually healthy and HLB symptomatic trees, at different times of the year, were analyzed to monitor the incidence and spread of HLB. The results showed that spread of Ca. Liberibacter asiaticus in an area may be detected a year or two before the development of HLB symptoms in plants. The study also suggests that garden stores and retail nurseries may have played a significant role in widespread distribution of infected psyllids and plants.