SURVEY FOR STRAINS OF XYLELLA-FASTIDIOSA IN CITRUS AFFECTED BY CITRUSVARIEGATED CHLOROSIS AND CITRUS BLIGHT IN BRAZIL

Polymerase chain reaction amplification of DNA from various strains of Xylella fastidiosa with tRNA consensus primers produced three differe nt fingerprint groups. The citrus variegated chlorosis (CVC) and mulbe rry leaf scorch strains were unique and readily separated from each ot her and all other strains tested. Internal primers were designed based on the sequence of a DNA fragment unique to the CVC strain. An assay was developed with a mixture of these primers and those reported to de tect 18 strains of X. fastidiosa. The assay was used to survey citrus in Brazil. The strain identified to be the cause of CVC was found in c onstant association with trees with CVC symptoms. On occasion, trees w ith no symptoms were found to have the CVC strain; this was presumably due to presymptomatic infections. No other strains were found in this survey, and X. fastidiosa was not associated with citrus blight.