Abstract: The aim of this study was to identify the sources of genetic resistance to stem canker and downy mildew in Brassica hybrids obtained from the crossings between five high yielding cultivars (Californium, Lisek, Jet Neuf, Górczański, Skrzeszowicki) of B. napus and eight Brassica species. The experiment was done in field and under controlled conditions using F2 and F3 generations of these interspecific hybrids. Moreover, the determination of Leptosphaeria species was studied using Loop-mediated DNA Amplification (LAMP) method. The genotypes differed with their reaction to the pathogens. Forms with increased resistance to blackleg especially among B. napus × B. carinata and B. napus × B. fruticulosa hybrids have been found. It was possible to select Brassica forms with lower susceptibility to downy mildew.