In a previous study, when resistant tomato plants (cv. Motelle) carrying the Sm gene were challenged with S. lycopersici, the SLNLCI gene was significantly upregulated. In this study, to verify the function of the SLNLCI gene response to disease resistance against S. lycopersici, virus-induced gene silencing (VIGS) was used to downregulate the expression level of the SLNLCI gene in resistant tomato plants inoculated with S. lycopersici. After inoculation with S. lycopersici, a susceptible phenotype was observed in the silenced SLNLCI-resistant plants. Through microscopy, impaired hypersensitive response (HR) and decreased ROS accumulation were also observed in the silenced SLNLCI plants. In addition, the production of lignin and callose were decreased in the silenced SLNLCI plants. Taken together, these results indicated that silencing the SLNLCI gene attenuated the resistance of tomato plants resistant to S. lycopersici. (C) 2018 Elsevier Inc. All rights reserved.