Development of a sensitive and reliable droplet digital PCR assay for the detection of 'Candidatus Liberibacter asiaticus'

Citrus Huanglongbing (HLB, yellow shoot disease) is one of the most serious citrus diseases worldwide. To better improve the detection sensitivity, a droplet digital PCR (ddPCR) assay was developed for the rapid detection of 'Candidatus Liberibacter asiaticus' (Las), the putative causal agent of HLB. The detection of sensitivity comparison using positive plasmid indicated that ddPCR was superior to quantitative PCR (qPCR) for detecting and quantifying Las at low concentrations. The Las detection of 40 field samples also showed that six of 13 asymptomatic samples (46.15%) with high Ct value (>35) were positive by ddPCR. This methodology showed great potential for early HLB infection diagnosis.