Detection of sugarcane leaf scald from latent infections

Leaf scald is one of the major bacterial diseases affecting sugarcane crop. Previous studies have reported the difficulty detection of the pathogen by conventional PCR when applied in asymptomatic plant material, where the pathogen population level is find below the detectable limit by conventional PCR. Because of this factor and the resilience of Xanthomonas albilineans at latent stage, our study aimed to enhance protocols, both extraction pro­cedures of sugarcane juice and DNA extraction protocols from sugarcane juice for the detection of Xanthomonas albilineans even when the residual bacterial sample is minimal. We tested four techniques for sugarcane juice extraction: compressor, pressing, macerated and bacterial flow in water and four DNA extraction protocols, two of them considered quick or simple, a CTAB procedure and one commercial Kit. The results indicated that conven­tional PCR was not able to detect the pathogen in asymptomatic stalks. However, working on Nested-PCR, we could detect X. albilineans in latently infected plants in 100% of samples when the vascular fluid was extracted by bacterial water flow following a centrifugation, adding TAE and boiling as DNA extraction method.