Genetic Relationships of Some Fastidious Xylem-Limited Bacteria

Abstract

Fastidious, gram-negative xylem-limited bacteria were examined for genetic relatedness to each other and to members of the major phytopathogen-containing genera of gram-negative bacteria. All of the xylem-limited bacterial strains studied had DNA base compositions of .apprx. 50.5 mol% guanine plus cytosine and genome MW of 1.4 .times. 109 .+-. 0.2 .times. 109. The results of DNA-DNA hybridization experiments suggested that these strains are all related at the species level, but supported distinction at the varietal level, and possibly at the subspecies level between the bacteria causing Pierce''s disease of grapevine and the bacteria causing phony disease of peach, plum leaf scald and periwinkle wilt. No relatedness was detected between the xylem-limited bacteria and Erwinia chrysanthemi, Pseudomonas syringae pv. [pathovar] syringae, Xanthomonas campestris pv. campestris or Agrobacterium tumefaciens.