CITRUS VARIEGATED CHLOROSIS-BACTERIUM - AXENIC CULTURE, PATHOGENICITY, AND SEROLOGICAL RELATIONSHIPS WITH OTHER STRAINS OF XYLELLA-FASTIDIOSA

A xylem-limited bacterium serologically related to strains of Xylella fastidiosa has been associated previously with citrus variegated chlor osis, a new and potentially serious disease of citrus in Brazil, When isolated and grown on PW (periwinkle wilt) medium, this gram-negative bacterium measured 0.4 X 4 mu m and was indistinguishable based on col ony appearance from reference strains of X. fastidiosa obtained from t he American Type Culture Collection, Rockville, MD. The bacterium also had a rippled cell wall typical of X. fastidiosa and induced symptoms typical of citrus variegated chlorosis in sweet orange after artifici al inoculation. The bacterium was reisolated from petioles of symptoma tic artificially inoculated plants, and its identity was confirmed by membrane entrapment immunofluorescence and Western blotting with antis erum UF-26 prepared against the original strain and extracts of petiol es and midribs from inoculated plants. The organism was observed in la rge numbers in xylem vessels of diseased, but not healthy, plant petio les and in extracts of diseased, but not healthy, petioles, using a go ld label with antiserum UF-26. The bacterium reisolated from symptomat ic plant tissue was culturally, morphologically, and serologically ind istinguishable from the strain used to inoculate the plants, completin g Koch's postulates. Antiserum UF-26 reacted most strongly with strain s of X. fastidiosa that cause diseases of grapevines, almond, ragweed, and oak. The citrus strain of X. fastidiosa also reacted as strongly as the homologous strain from plum to antiserum 1609-PP. This strain o f X. fastidiosa may represent a new serological group intermediate bet ween previously described serogroups of X. fastidiosa.