Abstract:In order to understand the resistance mechanism of casuarinas (Casuarina equisetifolia) against Ralstonia solanacearum, the changes in contents of tannin and phenols in casuarinas infected by R. solanacearum were analyzed. The results showed that the change trends of tannin and phenols contents in provenances with different resistibility were different. The contents of tannin and phenols in high- and media-resistant provenances increased at first and then decreased with the peak of 126 mg g-1, and the peak of media-resistant provenances came later. The susceptible provenances showed rising trend. After infected with R. solanacearum, the condensed tannin content increased gradually in three provenances, and that in the high-resistant provenances were 70.33% higher than that in susceptible provenances. The content of flavone in resistant provenances showed S type rising trend, while that in susceptible provenances increased slowly. Therefore, it was demonstrated that there were different defense mechanisms between resistant and susceptible provenances. The greater the content of secondary compounds increase, the stronger bacteriostasis and antioxidant activities, Casuarina equisetifolia would show higher resistance to bacterial wilt.