The discovery of a number of important points signaling pathways in studies of plant response to biotic stress was made possible by the use of mutants of the model plant Arabidopsis thaliana. The availability of mutants, a knock-out, obtained by chemical mutagenesis or insertion mutants line allows you to focus on a specific issue without the time-consuming research to create their own mutants. Plant resistance to necrotrophic fungi is dependent primarily on the biosynthesis and signaling pathway of jasmonic acid biosynthesis and accumulation and low molecular weight secondary metabolites, such as phytoalexins, which effectively inhibit fungal growth and colonization of plant tissues. The paper presents selected aspects of A. thaliana defense response to fungal attack nekrotroficznych dependent pathway of jasmonic acid and the production of kamaleksyny conditioned, and have been deciphering through the use of mutants.