Abstract: ObjectiveThe changes of related enzyme activities and endogenous hormone contents in different sugar-cane varieties during the long term interaction with smut fungus were studied to provide theoretical basis to illustrate the resistance mechanism of sugarcane to smut fungus infection.MethodThe smut-resistant variety GT29 and the smut-sus-ceptible variety Yacheng 71-3744 were selected to be inoculated with smut fungus by dipping method;the control group was treated with sterile water to conduct simulated inoculation with fungus.Sugarcane+1 leaf samples were taken at 30, 60,90 and 180 d respectively after the inoculation treatment,the changes of chitinase,β-1,3-glucanase and catalase (CAT)activities,and auxin(IAA),cytokinin(CTK)and ethylene(ETH)contents were analyzed.ResultDuring the entire infection period,activities of chitinase and β-1,3-glucanase and contents of IAA and CTK the two sugarcane varie-ties leaves showed the trends of gradual decrease or fluctuating decrease,and they reached the lowest level 180 d after ino-culation.But the activity of CAT showed an increasing trend and reached the highest level 180 d after inoculation.β-1,3-glucanase activity and ETH content in the smut-resistant variety GT29 were always higher than those in the smut-suscepti-ble variety Yacheng 71-3744 during the whole infection period.ConclusionPhysiological and biochemical responses of sugarcane to smut fungus stress are different at different growth stages,which may reflect different defense mechanisms between the susceptible variety and the resistant variety.