Abstract: TYLCV infected tomato variety ‘Cooperative 909 Red Tomato’ and TYLCV resistant tomato variety ‘Huamei 204’ were used as test materials, the effects of TYLCV on the expression levels of key factors in three defense signaling pathways in roots, stems and leaves of susceptible and resistant tomato varieties ‘Cooperative 909 Red Tomato’ and ‘Huamei 204’ were studied by fluorescence quantitative PCR,in order to understand the mechanism of tomato resistance to TYLCV.The results showed that 30 days after inoculation, the content of TYLCV in three organs of the TYLCV infected material ‘Cooperative 909 Red Tomato’ was significantly higher than that of TYLCV resistant material ‘Huamei 204’,and the content of root was the highest, followed by the stem, and the content of leaf was the lowest.The relative expression levels of salicylic acid pathway related genes PR1, NDR1 and TGA2.1 in leaves of ‘Cooperative 909 Red Tomato’ were significantly lower than ‘Huamei 204’,but higher than ‘Huamei 204’ in stems and roots.The relative expression levels of NDR1 and TGA2.1 were the highest in root, followed by stem and leaf.The relative expression levels of jasmonic acid pathway related genes LoxD and Pin2 in ‘Cooperative 909 Red Tomato’ were lower than ‘Huamei 204’ in leaves and stems, but higher than ‘Huamei 204’ in roots, with the highest relative expression levels in roots.The relative expression levels of ethylene pathway related genes ERF3 and EIN2 in leaves of‘Cooperative 909 Red Tomato’were lower than‘Huamei204’,but higher than‘Huamei 204’in stems and roots.The relative expressions of ERF3 and EIN2 were the highest in roots,followed by stems and the lowest in leaves.These results indicated the three signal transduction pathways of salicylic acid,jasmonic acid and ethylene were involved in the effect of tomato resistance to TYLCV.