Roots applicable, high sensitivity and specificity assay for the detection of Candidatus Liberibacter asiaticus in citrus roots and fruits

Candidatus Liberibacter asiaticus (CLas), a phloem-limited Gram-negative bacterium, is associated with citrus huanglongbing (HLB), which is one of the most destructive diseases currently threatening citrus production worldwide. No effective treatment for HLB is currently available. Effective prevention and control in the initial stage can block the spread and disease progression of HLB. Herein, we developed a co-detection assay for the 16S rDNA and 16S rRNA of CLas, the sensitivity of the co-detection assay was significantly increased over that of the single CLas DNA detection system. Beyond this, we found that the co-detection assay was a better fit to the root samples with higher population abundance than the previous reported detection system because it has a better specificity. Moreover, we found that the contents of 16S rRNA of CLas in citrus roots and fruits are significantly higher than that in leaves, which suggests that the time of HLB diagnosis is probably earlier by using these special tissues and the replication of CLas may become more active in these tissues, further suggested that the significance of study the mechanism of infection, prevention and control of HLB staring from these tissues.