Detection by PCR of Candidatus Liberibacter asiaticus, the bacterium causing citrus huanglongbing in vector psyllids: application to the study of vector–pathogen relationships

• Published in: Plant pathology Vol. 53; no. 1; pp. 96 - 102
• Main Authors: Hung, T.‐H., Hung, S.‐C., Chen, C.‐N., Hsu, M.‐H., Su, H.‐J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-02-2004; Blackwell; Wiley Subscription Services, Inc
• Subjects: Asian citrus psyllid; Biological and medical sciences; Candidatus; Candidatus Liberibacter asiaticus; citrus huanglongbing; Diaphorina citri; Fundamental and applied biological sciences. Psychology; mycoplasma; Phytopathology. Animal pests. Plant and forest protection; phytoplasma; Asian citrus psyllid; Plant pathology; Citrus fruit; Rutaceae; phytoplasma; Citrus; Polymerase chain reaction; Candidatus Liberibacter asiaticus; Dicotyledones; Angiospermae; Spermatophyta; Detection; citrus huanglongbing; Vector; mycoplasma
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/j.1365-3059.2004.00948.x

Citrus huanglongbing (HLB), previously called greening, is a serious citrus disease in Asia, eastern and southern Africa. It is caused by Candidatus Liberibacter asiaticus (Las), a phloem‐limited, nonculturable bacterium transmitted by the Asian citrus psyllid (Diaphorina citri) in Asia. A PCR‐based assay was developed for monitoring Las in vector psyllids using a rapid DNA extraction from psyllid bodies and PCR amplification. The entire procedure for Las detection in psyllids can be completed within 5 h. Using this method, Las can be accurately detected in psyllid adults as well as nymphs in different instar stages. The assay is sensitive enough for Las detection in single‐psyllid extract from adult, fifth, fourth and third instars. In a transovarial transmission experiment, Las was not detected in eggs or in offspring produced by Las‐carrying psyllid females. In a retention test, the Las‐carrying psyllids remained Las‐positive for 12 weeks after they were moved to common jasmine orange, a Las‐immune plant. From these experimental results it was concluded that Las persists in the Asian citrus psyllid vector, but is not transovarially transmitted by the vector. These data help in understanding epidemiological characteristics of Las and psyllids in citrus HLB.