Antimicrobial peptide MsrA1 is a synthetic hybrid molecule based on cecropin A from giant silk moth larvae and on melittin from melliferous bee venom. Transgenic potato plants of the Belarusian variety Odyssey with the constitutive expressiоn of msrA1 gene are shown to exhibit increased resistance to fungal pathogens Phytophthora infestans and Alternaria solani. Peroxidase genes expression studies using cDNA-PCR and DNA sequencing revealed the activation of the POX peroxidase gene in transgenic plants in the absence of pathogens. This may be indirect evidence of the increased formation of reactive oxygen species, which may explain special resistance to fungal pathogens. The data obtained also confirm a possible role of intracellular antimicrobial peptide in making the plants more resistant to oxidative stress by the way of activation of the host plant defense system.