Abscisic acid (ABA), a plant hormone involves in various plant physiological processes including, response to biotic and abiotic stress conditions. ABA was tested to study its ability to enhance disease resistance of two potato cultivars i.e., Nicola and Spunta, to the infection by the early blight fungus Alternaria solani (A. solani) under greenhouse conditions. Treatment with ABA solution (10 μM) reduced the early blight disease severity for both cultivars compared to the untreated infected plants. Differential display gene analysis for treated plants revealed three clear bands. These bands showed significant homology to well-known genes in the GenBank database and identified as superoxide dismutase (CuZnSOD), WRKY transcription factor (StWRKY) and Endoglucanase from potato genome. Real-Time PCR was used to detect the changes in gene expression of CuZnSOD and WRKY-type genes after infection with A. solani for both Nicola and Spunta potato cultivars and in different time intervals. The expression level of CuZnSOD and WRKY genes in potato leaves of both cultivars were increased for ABA treated and infected plants and for untreated/infected plants compared to the untreated/uninfected plants. Both genes were over expressed in infected plants treated with ABA than untreated ones and reached the maximum level of expression after two days of inoculation. The highest increase of both genes expression was observed in potato leaves of cv. Nicola compared to cv. Spunta.