Differential in vitro responses of rice cultivars to Italian lineages of the blast pathogen Pyricularia grisea. 2. Aromatic biosynthesis

Phenylalanine ammonia lyase (PAL)-specific activity levels were measured in suspension-cultured cells of six rice cultivars following treatment with cell wall hydrolysates prepared from seven Pyricularia grisea strains. Early after elicitation, even low hydrolysate concentrations were able to induce a significant increase in enzyme levels. However, neither rice genotypes showing differential sensitivity to blast reacted differently, nor did elicitors obtained from various pathotypes induce different reactions. At a later stage, higher hydrolysate concentrations were required to trigger maximal enzyme induction. Also in this case, only slight variations were detected in suspension cultures of a given cultivar treated with different elicitors. On the contrary, highly significant differences were observed among plant genotypes. A clear relationship was evident between the mean increase in PAL activity and the overall resistance to blast at the plant level. This trait could therefore represent a useful tool in selection for increased blast tolerance.