黄瓜苗期猝倒病侵染机制

Infection Mechanism of Cucumber Seedling Damping--off

本文明确了黄瓜猝倒病病原菌以瓜果腐霉菌为主。病菌侵染黄瓜幼苗主要是通过产生细胞壁降解酶,其中以PG,PMG,Cx为主,在活体条件下,病菌细胞壁解酶总活性与致病力正相关,但在离体条件下与致病力无关。说明两种情况下,病菌产生细胞壁降解酶的调控机制不同。侵染过程中PG,PMG先起作用,然后是Cx。寄主外渗物不仅为病菌提供营养,还含有一些细胞壁降解酶,但在种类及活性上与病菌的细胞壁降解酶不同。PG是诱导酶,被葡萄糖阻遏抑制。

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.