An evaluation of the genetic diversity of Xylella fastidiosa isolated fromdiseased citrus and coffee in Sao Paulo, Brazil

Strains of Xylella fastidiosa, isolated from sweet orange trees (Citrus sin ensis) and coffee trees (Coffea arabica) with symptoms of citrus variegated chlorosis and Requeima do Cafe, respectively, were indistinguish able base d on repetitive extragenic palindromic polymerase chain reaction (PCR) and enterobacterial repetitive intergenic consensus PCR assays. These strains w ere also indistinguishable with a previously described PCR assay that disti nguished the citrus strains from all other strains of Xylella fastidiosa. B ecause we were not able to document any genomic diversity in our collection of Xylella fastidiosa strains isolated from diseased citrus, the observed gradient of increasing disease severity from southern to northern regions o f Sao Paulo State is unlikely due to the presence of significantly differen t strains of the pathogen in the different regions. When comparisons were m ade to reference strains of Xylella fastidiosa isolated from other hosts us ing these methods, four groups were consistently identified consistent with the hosts and regions from which the strains originated: citrus and coffee , grapevine and almond, mulberry, and elm, plum, and oak. Independent resul ts from random amplified polymorphic DNA (RAPD) PCR assays were also consis tent with these results; however, two of the primers tested in RAPD-PCR wer e able to distinguish the coffee and citrus strains. Sequence comparisons o f a PCR product amplified from all strains of Xylella fastidiosa confirmed the presence of a CfoI polymorphism that can be used to distinguish the cit rus strains from all others. The ability to distinguish Xylella fastidiosa strains from citrus and coffee with a PCR-based assay will be useful in epi demiological and etiological studies of this pathogen.