The investigated researches were oriented towards studying the dynamics of development and evolution of diseases in tomato culture with the assessment of resistance comparative of plants to pathogens visualized in field conditions (Alternaria sp.; Stolbur disease mycoplasma and Tomato mosaic virus (TMV). The research results show us that the effects caused by the disease Alternaria sp., in tomato lines cultured by seedlings were contaminated with the percentage value of 68,7%, at the same time for the parental forms cultured by seeds this disease constituted maximum values of 89.1%. The difference between perspective lines and parental forms is 20.4%. The maximum size of the values obtained in parental forms exceeds by 21.6% the outlook lines for the Stolbur disease mycoplasma.