Objective To clarify the resistance and mechanism of red-leaved poplar P. deltoides cv. ‘Quanhong’ and its bud parental poplar P. deltoides ‘Zhonglin 2025’ against leaf rust, this study artificially inoculated Melampsora medusae Thüm on the Populus deltoides cv. ‘Quanhong’ and its parent P. deltoides ‘ Zhonglin 2025’.

Method In this study, the rust resistance differences between P. deltoides cv. ‘Quanhong’ and P. deltoides ‘Zhonglin 2025’, rust symptoms, gene expression of rust, dynamic changes of reactive oxygen species （ROS） and antioxidant enzyme activities in leaves of two poplars were determined.

Results The results showed that both poplars behaved as susceptible cultivarietas against M. medusae, of which P. deltoides cv. ‘Quanhong’ was moderately susceptible and P. deltoides ‘Zhonglin 2025’ was highly susceptible. Compared with P. deltoides cv. ‘Quanhong’, the rust clone developed faster in the leaves of P. deltoides ‘Zhonglin 2025’, with shorter latent period, and larger and denser uredia. The activities of three antioxidant enzymes （POD, CAT, SOD） of P. deltoides cv. ‘Quanhong’ were higher than P. deltoides ‘Zhonglin 2025’, while the ROS level was higher in P. deltoides ‘Zhonglin 2025’.

Conclusion The results suggests that P. deltoides cv. ‘Quanhong’ is able to activate innate immune response against M. medusae more quickly, balance ROS level and stronger disease resistance to rust accordingly.