ACCUMULATION OF PHENOLIC-COMPOUNDS IN LEAVES OF TOMATO PLANTS AFTER INFECTION WITH CLAVIBACTER-MICHIGANENSE SUBSP MICHIGANENSE STRAINS DIFFERING IN VIRULENCE

Infection experiments using tomato (Lycopersicon esculentum cv. Moneymaker) plants and three strains of Clavibacter michiganense subsp. michiganense were conducted. The bacterial isolates differed in plasmid status, virulence (measured as wilting index and as reduction of plant biomass) and the ability to colonize the plants. Differences in the expression of exopolysaccharides and the exoenzymes endocellulase, polygalacturonase, and xylanase, respectively, were not found with the bacterial isolates. As infection-induced responses of the plants time-depending increases in soluble phenolic material, including chlorogenic acid and rutin, in the steroid alkaloid tomatine and in cell wall-bound cinnamic acids were found. In the latter fraction p-coumaric, ferulic and especially caffeic acid were the main constituents. All plant responses were preferentially expressed in the compatible interaction. Sesquiterpenoid phytoalexins were not found in the infected plant tissues. The relation between bacterial pathogenicity and plant responses is discussed.