Loop-mediated Isothermal Amplification assay for Detection of Candidatus Liberibacter Asiaticus, a Causal Agent of Citrus Huanglongbing

Huanglongbing (HLB, Citrus greening disease) is one of the most devastating diseases that threaten citrus production worldwide. Although HLB presents systemically, low titer and uneven distribution of these bacteria within infected plants can make reliable detection difficult. It was known loop-mediated isothermal amplification (LAMP) method has the advantages of being highly specific, rapid, efficient, and laborsaving for detection of plant pathogens. We developed a new LAMP method targeting gene contained tandem repeat for more rapid and sensitive detection of Candidatus Liberibacter asiaticus (CLas), putative causal agent of the citrus huanglongbing. This new LAMP method was 10 folds more sensitive than conventional PCR in detecting the HLB pathogen and similar to that of real-time PCR in visual detection assay by adding SYBR Green I to mixture and 1% agarose gel electrophoresis. Positive reactions were achieved in reaction temperature 57, 60 and $62^{\circ}C$ but not $65^{\circ}C$. Although this LAMP method was not more sensitive than real-time PCR, it does not require a thermocycler for amplification or agarose gel electrophoresis for resolution. Thus, we expect that this LAMP method shows strong promise as a reliable, rapid, and cost-effective method of detecting the CLas in citrus and can be applied for rapid diagnosis is needed.