Abstract:

In this study, the activity changes of key enzymes in phenylpropanoid pathway including phenylalanine ammonia lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate:coenzyme A ligase (4CL) were determined to obtain information on the mechanism of Astragalus membranaceus against root rot pathogens, so as to provide reference for disease resistance breeding. Regarding A. membranaceus var. mongholicus and root rot pathogens as the interaction system, the dynamic activity changes of the three enzymes were measured by spectrophotometry methods with the A. membranaceus being inoculated with Fusarium solani and F. acuminatum respectively using the root-dipping method. The results showed that both PAL and C4H in Astragalus infected by F. solani had a significantly higher activity than their counterparts in the control, and both had enzyme activity peaks at 7 d and 21 d, respectively; the activity of 4CL steadily increased with the time and was also significantly higher than that of the control at 7 d and 21 d. In the case of Astragalus infected by F. acuminatum, the activities of all three enzymes in treatment were significantly higher than that in the control at 21 d. It can be seen that during the infection of both pathogens, the key enzymes in phenylpropanoid pathway are activated to some extents, but differ in the time and pattern of being activated, which indicates that A. membranaceus has obvious different disease-resistant mechanisms against the infection of F. solani and F. acuminatum.

Key words: Astragalus membranaceus var. mongholicus, root rot pathogens, phenylpropanoid pathway, key enzymes, activity change