低濃度に感染した野外試料から Candidatus Liberibacter asiaticus を検出する場合における遺伝子増幅法による陽性率の違い

Polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and quantitative PCR (qPCR) were used to detect low-level Candidatus Liberibacter asiaticus infection in citrus trees, and their results were compared. Sample DNA was prepared from the developing shoots of Citrus depressa and Citrus tankan that were spontaneously infected with Ca. L. asiaticus. The concentrations of the homologous region of the tufB gene of Ca. L. asiaticus were estimated by qPCR analysis using serially diluted plasmid DNA containing the tufB gene region as a calibration standard. All DNA samples from which the specific amplification product was detected by PCR also gave positive results in the LAMP analysis, and qPCR gave positive results for all samples that were positive in the LAMP analysis. Therefore, we concluded that qPCR is the most sensitive method for detecting low-level Ca. L. asiaticus infection.