RELATEDNESS OF PSEUDOMONAS-SYRINGAE PV TOMATO, PSEUDOMONAS-SYRINGAE PV MACULICOLA AND PSEUDOMONAS-SYRINGAE PV ANTIRRHINI

The relationships among strains of Pseudomonas syringae pv. tomato, Ps. syr. antirrhini, Ps. syr. maculicola, Ps. syr. apii and a strain isolated from squash were examined by restriction fragment length polvmorphism (RFLP) patterns, nutritional characteristics, host of origin and host ranges. All strains tested except for Ps. syr. maculicola 4326 isolated from radish (Raphanus sativus L.) constitute a closely related group. No polymorphism was seen among strains probed with the 5-7 and 2.3 kb EcoRI fragments which lie adjacent to the hrp cluster of Ps. syr. tomato and the 8.6 kb EcoRI insert of pBG2, a plasmid carrying the beta-glucosidase gene(s). All strains tested had overlapping host ranges. In contrast to this, comparison of strains by RFLP patterns of sequences homologous to the 4.5 kb HindIII fragment of pRut2 and nutritional properties distinguished four groups. Group 1, consisting of strains of pathovars maculicola, tomato and apii, had similar RFLP patterns and used homoserine but not sorbitol as carbon sources. Group 2, consisting of strains of pathovars maculicola and tomato, differed from Group 1 in RFLP patterns and did not use either homoserine or sorbitol. Group 3 was similar to Group 2 in RFLP patterns but utilized homoserine and sorbitol. This group included strains of the pathovars tomato and antirrhini, and a strain isolated from squash. Group 4, a single strain of Ps. syr. maculicola isolated from radish, had unique RFLP patterns and resembled Group 3 nutritionally. The evolutionary relationships of these strains are discussed.