Phomous rot is a dangerous disease of potato tubers

Goal. To establish the symptoms of pathogens of fomose rot on potato varieties of different resistance, to isolate pathogens from the genus Phoma, parasitizing on tubers and stems of plants. Methods. Symptoms of phomotic rot were determined visually by the determinant of diseases and the method of microbiological diagnosis was used. Pathogens were isolated from stems and tubers affected by fomose rot. Results. On the basis of psychopathological examination, it was experimentally proved for the first time in Ukraine that fomozna potato rot is widespread in commodity and seed potato plantings. The degree of harmfulness reaches 35%. Pathogens of the genus Phoma (Ph. Solanicola Prill. Et Del Ph tuberosa Malkomcon) affect potato stems and tubers. On the stems, the first symptoms appear as spots during the flowering phase of the plants, and on tubers the gangrene appears as round, depressed and hard spots, light or dark brown in color, on the top of which pycnids form. According to the harmfulness of the pathogen, the Polesye of Ukraine is divided into three zones: 1. The zone of strong development includes the Volyn and Zhytomyr regions, where the number of affected plants with phomosis exceeds 5%, affected tubers — 8—10%; 2. The zone of moderate development, it includes the Rivne and Khmelnitsky regions, where the number of plants affected by phomosis is 2—3%, and tubers during storage of the crop — 5—7%; 3. The zone of insignificant development of the disease includes Kiev and Chernihiv regions, where the number of plants affected by gangrene is up to 2%, and tubers after storage of the crop — up to 4%. Conclusions. According to the results of psychopathological surveys, three zones of development of fomose rot of potatoes (severe, moderate and minor damage to phomosis) were identified and a scheme for the development cycle of the infection of the genus Phoma (Solanicola Prill. et. Del. And Ph. Tuberosa Melh.) was established. Symptoms of fomose rot appear on the stems in the form of elongated blurry spots, on which pycnids form from light brown (Eurostar) to dark brown (Riviera) color. On potato tubers, fomosis appears in the form of round, hard, sunken spots of a dark color. It is proved that during the interaction of potato plants with pathogens of the genus Phoma complex physiological, biochemical and pathological processes occur that significantly reduce productivity, quality, taste and other economically valuable traits.