Relationship between eucalyptus resistance to eucalyptus dieback and defense enzyme system

In order to determine the biochemical index, which indicates resistance of eucalyptus to eucalyptus dieback (Cylindrodadium quinqueseptatum Morgan), 11 eucalyptus cultivars were selected from Fujian Province and the activities of two major defense-enzymes, peroxidase (POD) and superoxide dismutase (SOD), analyzed. The results show that POD and SOD activities of healthy or infected leaves of the 11 cultivars change in a regular manner in the following order: resistant cultivar > moderate resistant cultivar > moderate susceptible cultivar > susceptible cultivar. POD isozyme band shows no regularity with resistance to eucalyptus dieback before or after inoculation, while SOD isozyme band has a relatively positive relation to the resistance to eucalyptus dieback. In relation to breeding, POD and SOD activity before and after inoculation and SOD isozyme bands after inoculation can be used as early biochemical indexes for resistance of eucalyptus to eucalyptus dieback.