In the world's cotton-growing countries, cotton is cultivated on the territory of 89 countries, on a total area of more than 30 million hectares, from which more than 22.4 million tons of cotton fiber are obtained. Today, there are problems in the production of high-quality cotton fiber yield. One of these problems is pathogens that cause significant damage to cotton production, with losses in the world amounting to 12-15%. In the world, considerable attention is paid to the study and control of the pathogen Verticillium dahliae Klebahn, which affects cotton. The problem of breeding wilt-resistant varieties of cotton is complicated by the search for new methods and donors of resistance to the pathogen. It is necessary to improve the method of selection of parent pairs during hybridization and qualitative assessment of interspecific hybrids at the early stages of the breeding process in order to increase the efficiency of breeding, speed up the process of introducing new varieties of cotton into production.The selection must be carried out on the basis of physiology and biochemistry of signs of resistance of the initial breeding material. The initial stage of selection should be based on test signs of resistance, which are associated with the catalytic activity of some enzymes involved in the formation of phytoimmunity against fungal infections (peroxidase, phenylalanine ammonialyase, polyphenol oxidase).The greatest interest of researchers is attracted by protective mechanisms, including the processes of lignification of cell walls and the biosynthesis of phenolic phytoalexins. These mechanisms simultaneously create a mechanical and chemical barrier to the penetration of fungal structures into the cell, preventing the spread of the pathogen