Abstract: ObjectiveThis research was conducted to understand the resistance characteristics of tobacco germplasm resource TI203 to Tobacco mosaic virus(TMV),in order to provide more information for parent selection in disease resis-tant breeding of tobacco.MethodTobacco germplasm resource TI203 was taken as experimental material. The resistance specificity of TI203 to TMV,and symptom and level of virus replication of TI203 after inoculated with TMV ordinary strain(TMV-U1 strain)were studied by TMV inoculation,disease investigation,virus coat protein accumulation detec-tion,TMV replication level determination and observation on sunburn phenomenon.ResultThe results showed that TI203 exhibited a symptomless reaction to TMV,but typical symptoms to Potato virus Y(PVY)and Cucumber mosic vi-rus(CMV)after inoculation. Western blotting detection results indicated that the level of virus replication in TI203 leaves was obviously lower than that of control variety 14 d after inoculated with TMV-U1 strain. Resistance of TI203 to TMV was observed at virus replication level by using TMV-GFP infectious clone infiltration inoculation. Under high tempera-ture and strong sunlight conditions,sunburn phenomena always occurred on fast-growing middle and upper leaves of TI203,and the leaves were difficult to recover.ConclusionTI203 is symptomless to TMV and its resistance to TMV occurs at virus replication level.