Aim. To investigate the phylogenetic relations of P. melonis strain 502 and to study the varietal sensitivity of cu- cumber plants to P. melonis strain 502. Methods. DNA was extracted using the enzymatic lysis buffer. The PCR was conducted following White et al. protocol (1990). The obtained PCR-products were determined by sequencing on the automatic capillary sequencer Applied Biosystems ABI Prism 3130. The sequence of the gene 5.8S rRNA of P. melonis strain 502 was compared to the sequences from the GenBank database using the BLAST analysis. The phy- logenetic analysis was conducted by the neighbor-joining method. The evolutionary distances were estimated by the method of Jukes & Cantor. The evolutionary analysis was conducted in MEGA7. The sensitivity of cucumber plants was determined during a vegetative experiment with artificial infection background (AIB), created by introducing the infectious material of fungus P. melonis strain 502 into the soil. The infectious material was introduced at a rate of 50 thousand CFU/per 1 g of soil. The damage to the root system was assessed after 14 days of cultivating plants on the AIB. The disease severity index (DSI) was estimated to determine the general sensitivity of the investigated varieties. The varieties, which received DSI