AFLP fingerprinting: an efficient technique for detecting genetic variation of Xanthomonas axonopodis pv. manihotis

Xanthomonas axonopodis pv. manihotis (Xam) is the causative agent of cassav a bacterial blight (CBB), a worldwide disease that is particularly destruct ive in South America and Africa. CBB is controlled essentially through the use of resistant varieties. To develop an appropriate disease management st rategy, the genetic diversity of the pathogen's populations must be assesse d. Until now, the genetic diversity of Xam was characterized by RFLP analys es using ribotyping, and plasmid and genomic Xam probes. We used AFLP (ampl ified fragment length polymorphism), a novel PCR-based technique, to charac terize the genetic diversity of Colombian Xam isolates. Six Xam strains wer e tested with 65 AFLP primer combinations to identify the best selective pr imers. Eight primer combinations were selected according to their reproduci bility, number of polymorphic bands and polymorphism detected between Xam s trains. Forty-seven Xam strains, originating from different Colombian ecozo nes, were analysed with the selected combinations. Results obtained with AF LP are consistent with those obtained with RFLP, using plasmid DNA as a pro be. Some primer combinations differentiated Xam strains that were not disti nguished by RFLP analyses, thus AFLP fingerprinting allowed a better defini tion of the genetic relationships between Xam strains.