Developpment of a new multilocus Variable-Number Tandem Repeat typing scheme for the global surveillance of #Xanthomonas citri pv. Citri# : Poster 19

Abstract : MultiLocus Variable number of tandem repeats Analysis (MLVA) has been extensively used for addressing epidemiological and evolutionary questions 0 11 bacteria pathogenic to humans (Ciammaruconi el al., 2008). This typing scheme was shown especially useful for the so-called monomorphic pathogens, which can be efficiently genotyped with a high throughput by MLVA. In contrast, it has been scarcely used for bacterial plant pathogens despite the tremendous impact of some of them. We developed an optimized MLVA scheme targeting long tandem repeats (2: 10 bp) for assessing the global epidemiology of the c itrus pathogen Xanthomonas citri pv. citri (Xcc). Xcc is a quarantine organism in several countries and a significant threat for the citrus industry worldwide. We screened the genome of Xcc strain IAI'AR 306 and of phylogenetically related xanthomonads for tandem repeals. The resolution at 31 polymorphie loci (MLVA3 1) was assessed using 129 strains of Xcc representative of the currently known genetic and pathological diversity of the pathogen worldwide. Based on Discriminant Analys is of Principal Components (DAPC), seven mostly pathotypespecifie genetic clusters were defined. DAPC c1uster 1 had a much wider geographical distribution than others. This single DAPC c1uster has been primarily implicated in the major geographical extension of Xcc during the XXth century. Because of the suboptimal inter-laboratory reproducibility of AFLP and rep-PCR, MLVA-31 represents an opportunity for international genotyping data sharing. (Texte intégral)