Abstract

Changes in various physiological defenses including secondary metabolites, proline, total soluble protein and antioxidant enzymes were investigated in leaves and stems of 18 flax lines either resistant or susceptible to powdery mildew. The results showed that the total alkaloids content in flax stems was significantly increased in resistant lines when compared with resistant parent, but significantly decreased in susceptible lines and susceptible parent when compared with resistant parent. Stems of the resistant flax lines had a higher content of total phenols than susceptible ones upon pathogen challenge. Infection with powdery mildew significantly increased peroxidase, polyphenol oxidase and catalase activities in leaves of flax lines when compared with either resistant or susceptible parents as well as proline content. This increase was much pronounced in tolerant lines than resistant lines. Total soluble protein content in flax leaves increased significantly in resistant lines when compared with resistant parent but decreased significantly in susceptible lines when compared with resistant parent.

Key words: Flax, antioxidant enzymes, phenol, proline, secondary metabolites, powdery mildew.

Abbreviation

ROS, Reactive oxygen species; POX, peroxidase; SOD, superoxide dismutase; CAT, catalase; APX, ascorbate peroxidase; PPO, polyphenol oxidases.