Abstract
The polymerase chain reaction (PCR) was used with an internal control to exclude false-negative reactions in a citrus huanglongbing (HLB) assay. Degenerated primers, CSSF-1 (5'-GACACTGTTGGWCAGTATGA-3') and CSSR-1 (5'-TCRTACAVTGCAGGTTGCAC-3'), for the internal control were constructed based on the sucrose synthase genes of Citrus unshiu, Medicago sativa, Daucus carota, Arabidopsis thaliana and Phaseolus vulgaris. Multiplex PCR with the CSS primer and the Ol1-Ol2c primer amplified two DNA fragments corresponding to the sucrose synthase gene and the ‘Candidatus Liberibacter asiaticus’ 16S rDNA gene from ‘Candidatus L. asiaticus’ infected citrus DNA, respectively. A DNA fragment of the sucrose synthase gene was solely amplified from healthy samples. No amplified fragment was detected in incomplete reactions.
