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

Phenylalanine ammonia lyase specific activity levels were measured in suspension cultured cells of six rice cultivars following the 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 of enzyme levels. However, neither rice genotypes showing differential sensitivity to blast reacted differently, nor elicitors obtained from various pathotypes induced different reactions. At a later stage, higher hydrolysate concentrations were required to trigger maximal enzyme induction. In this case also, only slight variations were detected in suspension cultures of a given cultivar treated with different elicitors. On the contrary, highly significant differences were disclosed among plant genotypes. A remarkable relationship was evident between the mean increase in phenylalanine ammonia lyase activity and the overall resistance to blast at the plant level. This trait could therefore represent a useful tool aiming at the selection for increased blast tolerance