| Chito-oligosaccharide is a species of linear polymers, in which 2-10 D-glucosamine residues are connected byβ-1, 4 linkages. The induced resistance of chito-oligosaccharides (DP=3-10) to Tobacco mosaic virus (TMV) was studied. The main content of research included the effects to symptom expression and the changes of defence enzymes after chito-oligosaccharides treatment.(1) Tobacco plants expressed induced systemic resistance to TMV by treatment of chito-oligosaccharides (10μg/mL-200μg/mL). The day of symptom-appearing was 3d delayed averagely, and systemic symptoms were remarkably reduced, and the average severity was 3 grade decreased. .(2) The content of chlorophyll in mesophyll cells of tobacco plants after treatment of chito-oligosaccharides (10μg/mL-200μg/mL) was 124.0%-187.6% as high as that of untreated plants. Besides, treatment of chito-oligosaccharides also increased the content of chlorophyll in healthy plants (without inoculation with TMV).(3) The epidemiological effects of chito-oligosaccharides treatment on disease development of tobacco mosaic were studied. Applying software Curve Expert 1.3, we set up a mathematic model of disease progress in one infection cycle of TMV in induced plants. The curve of severity increase of tobacco mosaic after chito-oligosaccharides treatment was fitted to logistic model y=a/[1+b*exp(-cx)] (y : average severity, x : days after inoculation). Using software MATLAB6.5, we analyzed the severity progress curves. The results indicated that the severity did not reach 5 in treatments of 10μg/mL-50μg/mL, and days of reaching severity 5 in treated plants at 100μg/mL-200μg/mL were 5.6d-7.7d delayed respectively than untreated plants; the decrease rate of disease severity were between 18.9% and 55.6% in treated plants at 10μg/mL -200μg/mL; the AUDPCs were 41.4%-76.4% decreased than...
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