The phytoalexin camalexin is not metabolized by Phoma lingam, Alternaria brassicae, or phytopathogenic bacteria

The metabolism of the cruciferous phytoalexin camalexin by the backleg (Lep tosphaeria maculans (Desm.) Ces. et de Not., asexual stage Phoma lingam (To de ex Fr.) Desm), and blackspot (Alternaria brassicae (Berk.) Sacc.) fungi, as well as the phytopathogenic bacteria Pseudomonas syringae, P. cichorii, Erwinia carotovora, and Xanthomonas campestris was evaluated. The micro-or ganisms were incubated with camalexin for different time periods and the cu ltures were extracted and analyzed by high performance liquid chromatograph y and proton nuclear magnetic resonance. The results of these analyses indi cated that camalexin was not metabolized by any of the micro-organisms. Imp ortantly, camalexin appeared to inhibit the production of the phytotoxin de struxin B by A. brassicae, but did not affect the phytotoxins produced by P . lingam. Furthermore, the growth of bacteria and fungi was inhibited almos t completely in the presence of camalexin at concentrations greater than or equal to 0.40 mM. (C) 1998 Published by Elsevier Science Ireland Ltd.