Comparison of methods for identification of the sugarcane pathogen Xanthomonas albilineans.
The Biolog metabolic system, sweet corn pathogenicity assays and rep-PCR fingerprinting were compared for identification of X. albilineans. The study was conducted with 27 isolates of X. albilineans, 2 isolates of X. oryzae pv. oryzae, 1 isolate of Xanthomonas fragariae and 1 isolate each of 6 pathovars of Xanthomonas campestris. Acetobacter diazotrophicus, Clavibacter xyli subsp. xyli, Escherichia coli, Erwinia herbicola and several unknown bacterial species isolated from sugarcane were also included in the PCR assays. Biolog allowed correct identification of X. albilineans in 31% of the cases. Sweet corn pathogenicity assay and PCR allowed correct identification of all isolates, and a clear separation of X. albilineans from all other bacteria tested. PCR fingerprints were reproduced when cell lysates from liquid cultures or individual colonies, instead of purified DNA, were used. Pathogenicity in sweet corn required a period of 20-30 days for symptom expression. Rep-PCR results were produced in a few hours, identifying X. albilineans and providing a faster diagnosis of the sugarcane leaf scald disease.