Abstract:

The leaf structure，reactive oxygen species generation，antioxidant enzyme activities，polyamine contents，and expression profiles of polyamine synthesis related genes were compared between a resistant melon variety（Yuntian 930）and a susceptible cultivar（0544）after the inoculation with Podosphaera xanthii. The results showed that the bristles number，waxes content，and ratio of palisade/spong were significantly higher in‘Yuntian 930’than those in‘0544’. After inoculation with P. xanthii，the contents of H₂O₂，，and MDA in‘0544’rose more slowly and kept a lower level in‘Yuntian 930’than in‘0544’. However，the activities of SOD，POD，CAT in‘Yuntian 930’were markedly higher. In addition，the polyamine content and the abundance of polyamine synthesis related genes were increased quickly and reach higher levels in‘Yuntian 930’than those in‘0544’，after the inoculation with P. xanthii. These results indicated that，the higher resistance to powdery mildew in‘Yuntian 930’was related to the leaf morphological structure，higher antioxidant capacity，and higher polyamine synthesis capability.

Key words: melon, powdery mildew, leaf structure, reactive oxygen species, antioxidant enzyme, polyamine, gene expression