Identification of Salicylic Acid Conferred Resistance Genes against Gray Leaf Spot Disease in Tomato

Tomato gray leaf spot is a main disease in tomato production.Induced resistance to pathogen infection is a widely accepted environmentally friendly strategy.In this study, we aimed to discover the key disease resistance genes induced by exogenous applications of the hormone salicylic acid (SA).Our results showed that, under treatment with 0.2 mM SA, strong resistance to gray leaf spot was induced in the leaves of tomato seedlings, and a significant reduction in the number of lesions and in disease index accompanied the application of SA.The content of active oxygen and enzyme activities increased with SA treatment, including those of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD).In addition, RT-PCR results showed that the expression levels of a series of defense genes, such as members of the WRKY65, pathogenesis-related (PR), MAPK and abscisic acid (ABA) receptor PYR/PYL families, significantly increased in response to SA treatment.The results indicated that applications of the exogenous hormone SA can enhance the resistance to S. lycopersici in the susceptible cultivar "Moneymaker" by regulating the expression of genes related to disease resistance.