The influence of sequential exposure of 5 x 10(-5) M salicylic acid (SA) or 1 x 10(-7) M jasmonic acid (JA) and endophytic bacterium Bacillus subtilis strain 26D on peroxidase activity, transcription of the M21334 isoperoxidase gene from potato (Solarium tuberosum L.), and the formation of resistance to the infective agent of potato blight Phytophthora infestans (Mont.) de Bary was studied. It was found that individual application of JA or Bacillus subtilis 26D and sequential application of SA and B. subtilis 26D were the most effective in protecting plants against pathogens, while sequential application of JA and B. subtilis 26D drastically suppressed plant resistance. The results suggest the need for strict compliance with regulations when using SA and JA, as well as biological products based on living bacteria as modern plant protection products with immunomodulatory properties that trigger specific signaling pathways, which often interfere with each other.