Oral Technical Session: Disease Diagnosis and Detection

10-O

Live bacterial population dynamics of ‘Candidatus Liberibacter asiaticus’, the bacterial agent associated with citrus huanglongbing, in two plant hosts.
H. HU (1), R. H. Brlansky (1)
(1) CREC, IFAS, University of Florida, Lake Alfred, FL, U.S.A.

Citrus Huanglongbing (HLB) is a century-old destructive disease which presents an unprecedented challenge to citrus industries worldwide. In Florida, HLB is associated with the phloem-limited bacterium ‘Candidatus Liberibacter asiaticus’ (Las), and is mainly transmitted by Asian citrus psyllid (Diaphorina citri). Quantification of the pathogen population in a host aids in investigation of virulence mechanisms and disease management. Recently a procedure was developed to detect live bacterial populations using a novel DNA-binding dye, propidium monoazide, with real-time polymerase chain reaction (PMA-qPCR). From August 2010 to April 2012, the change of the live Las populations in psyllid-inoculated sweet orange (Citrus sinensis ‘Valencia’) and Chinese Box Orange (Severinia buxifolia) plants was monitored by PMA-qPCR. Our results showed that the live Las population was lower from August 2010 to March 2011, and significantly higher live populations developed from April 2011 in both hosts. No obvious pattern in the total bacterial population was observed in either host. This pattern may indicate a seasonal growth of Las along with the growth of both plants. These new findings should provide useful information on HLB.