Comparison between Serological and Molecular Detection of Citrus Canker Pathogen (<i>Xanthomonas axonopodis</i> pv. <i>citri</i>)

Abstract

The specificity and sensitivity of serological and molecular tools for the detection of citrus canker pathogen ( Xanthomonas axonopodis pv. citri; Xac ) were investigated and compared. Virulence Xac BP210 was used as antigen for antisera production. The sensitivity of 1: 2,000 diluted antisera were at 106 CFU/mL for live cell and 105 CFU/ml for dead cells. The cross-reaction of the antisera was observed only with X. campestris pv. vesicatoria but not other Xanthomonas nor other unrelated bacteria tested. Molecular tool was performed using specific primer to the rpf gene on Xac. The PCR amplification indicated that, all Xac isolates amplified a product of 581 bp which was not seen in other Xanthomonas sp. and unrelated bacteria tested. The sensitivity of these specific primers were down to at least 1 cell which were effective to detect the pathogen in both infected symptomatic and asymptomatic lime tissues. While, serological tool was able to detect the pathogen only on infected leaves of day 4 post inoculation when the symptom was already appeared. The serological tool can be used to detect and quantify the present of Xac to study the disease development on symptomatic tissues.