"Leaf blight caused by Cylindrocladium quinqueseptatum Boedijn & Reitsma is a major disease occurring in Eucalyptus plantlets and saplings worldwide. Current studies on the resistance to this disease in eucalypti have focused primarily on analyzing the relationship between the disease and the metabolic products from the anatomic structure of Eucalyptus leaves and their physiological responses to pathogen invasion. There have been no reports on the mechanisms of molecular responses. Previous research suggests that Eucalyptus grandis × Eucalyptus urophylla 9224 is the highest resistant cultivar among the 11 ones planted in Fujian Province. Therefore, in this study, the molecular responses of E. grandis × E. urophylla 9224 to C. quinqueseptatum were investigated by means of suppression subtractive hybridization (SSH). In total, 928 clones were obtained from the forward SSH cDNA library of E. grandis × E. urophylla 9224, and 25 up-regulated genes were identified by screening the library using the method of reverse northern hybridization. The results show that among these, 23 up-regulated genes with known functions were involved in signal transduction, plant resistance response, photosynthesis, energy transfer, protein metabolism, and plant growth."