Abstract:

【Objective】 Electron microscope technique was used to study the inhibitory effects of oligosaccharide on the infection of Puccinia helianthi on sunflower, to unravel the mechanism of oligosaccharide elicitors at the cytology level. 【Method】Treated with oligosaccharide, 2 days later, sunflower was inoculated with Puccinia helianthi, the ultrastructure of pathogen and host was investigated with scanning and transmission electronic microscopy. 【Result】 Some uredospores on the induced plant were sunken and the germination was inhibited. The host cells of sunflower produced defense structures and material related to the infection. The host cell wall was thickened and deeply stained，dark material deposited under the cell wall and the walls of haustoria thickened and extra-haustorial matrix was found to be enlarged; some haustoria became malformed and disintegrated, deformation and vacuolation of host organelles occured，finally the whole host cell disintegrated，collapsed. 【Conclusion】 Oligosaccharide has inhibitory effects on the pathogen infection and sunflower leaves were induced resistance to the rust disease.

Key words: sunflower rust, oligosaccharide, inhibitory effects, induced resistance, ultrastructure