Abstract:

【Objective】 The objective of the experiment was to investigate the inducing effects of benzothiadiazole (BTH), salicylic acid (SA) and nanometer silicon (SiO2) spraying on disease resistance of melon to powdery mildew and its relationship to hydroxyproline-rich glycoprotein(HRGP) and lignin contents in leaves. 【Method】 Two melon cultivars with different powder mildew susceptibilities, Yindi and Kalakesai, were employed as materials. At the fifth day after BTH, SA and SiO2 spraying, seedlings were inoculated with Sphaerotheca fuliginea, and disease indexes, leaf lignin and HRGP contents were determined for four times at alternate days. 【Result】 BTH and SA spraying significantly decreased disease indexes of powdery mildew in melon seedlings especially by BTH spraying and on the resistant cultivar, while SiO2 spraying showed a significant effect only in the initial days after treatment. Leaf lignin and HRGP content increased significantly and systemically in melon seedlings induced by Sphaerotheca fuliginea inoculation and BTH, SA spraying, while SiO2 had no such effect. The accumulation of lignin and HRGP in leaf cell wall was synchronous obviously, and was higher in the resistant cultivar than in the susceptible one. 【Conclusion】 The accumulation of HRGP and the deposition of lignin in cell wall of melon leaves are related to its resistant reactions to powdery mildew, and it is one of the important biochemical mechanisms in melon-Sphaerotheca fuliginea interactions.

Key words: Cucumis melo L., powdery mildew, benzothiadiazole, salicylic acid, SiO2, lignin, HRGP