Strains of Xylella fastidiosa rapidly distinguished by arbitrarily primed-PCR

Genomic DNAs isolated from strains of Xylella fastidiosa that caused citrus variegated chlorosis, coffee leaf scorch, Pierce's Disease of grapevine, a nd plum leaf scorch were analyzed by arbitrarily primed polymerase chain re action. Purified DNA was amplified under nonstringent conditions with singl e primers 21 nucleotides (nt) long. Thirty-nine amplification products were observed that were useful to distinguish among the strains and to derive a similarity matrix and construct a phenogram showing possible relationships among the strains. Strains isolated from diseased coffee and citrus in Bra zil were closely related to each other (coefficient of similarity of 0.872) , but only distantly related to a strain isolated from diseased grapevine i n the USA (coefficient of similarity of 0.650). Strains of Xylella fastidio sa isolated from diseased plums in the USA and Brazil clustered with strain s from different hosts isolated from their respective countries of origin. Thus, there may be two quite dissimilar clusters of strains of Xylella fast idiosa, one in North America and the other in South America. Each cluster c ontains strains that can cause disease in plum. The methods described provi de a convenient and rapid method to distinguish between strains of Xylella fastidiosa that cause diseases of coffee and citrus in the same region of B razil. This has not been possible previously. This will potentially enable the two strains to be distinguished in alternate hosts or in insect vectors .