黄瓜苗期猝倒病侵染机制

Infection Mechanism of Cucumber Seedling Damping--off

Major pathogen causing cucumber seedling damping-off has been identi- fied as Pythium aphanidermatum. The pathgen, by production of cell wall- degrading enzymes (CWDE), attacked host, Among cell wall degrading enzymes, PG, PMG and Cx were predominant. It was shown that total enzyme activity of these enzymes from pathogen was affirmatively correlative to the fungi virulence in vivo rather than in vitro. Rsulte suggested that these degrading enzymes functioned in plant exactly follow- ing a certain sequence in which PG and PMG work firsk, then Cx does, host exudates not only provided nutrients for pathogen but also contained some cell wall degrading enzymes which, however, were different from those of pathogen in kinds and activity; PG belonged to an inductive enzyme and was inhibited by glucose through catabolite repression.