Assessment of the genetic diversity of Xylella fastidiosa isolated from citrus in Brazil by PCR-RFLP of the 16S rDNA and 16S-23S intergenic spacer and rep-PCR fingerprinting

The genetic diversity among twenty three strains of Xylella fastidiosa, iso lated from sweet orange citrus, was assessed by RFLP analysis of the 16S rD NA and 16S-23S intergenic spacer and by rep-PCR fingerprinting together wit h strains isolated from coffee, grapevine, plum and pear. The PCR products obtained by amplification of the 16S rDNA and 16S-23S spacer region were di gested with restriction enzymes and a low level of polymorphism was detecte d. In rep-PCR fingerprinting, a relationship between the strains and their hosts was observed by using the BOX, ERIC and REP primers. Two major groups were obtained within the citrus cluster and relationships to the geographi c origin of the strains revealed. Citrus strains isolated from the States o f Sao Paulo and Sergipe formed one group and strains from the Southern Stat es formed another group. Distinct origins of X. fastidiosa in the Southern and Southeastern States is postulated. The pear isolate was distantly relat ed to all of the other X. fastidiosa strains.