Field-Based Evaluation of Reactive Oxygen Species Treatments and Fungicide Protections in Potato: Effects on Late Blight, Plant Nutritional Status, Yield, and Tuber Quality

The aim of the study was to determine, under field conditions, the effects of O3, H2O2, and fungicide protection on potato late blight severity, SPAD values, tuber yield, and mineral composition, and additionally to assess whether the number of ozone applications modifies selected tuber quality traits. Two complementary field experiments were conducted in 2017 and 2018. In the main experiment, control, fungicide protection, ozone fumigation, and foliar H2O2 treatments were compared with respect to late blight severity, SPAD response, yield, and macro- and micronutrient contents in tuber peel and flesh. In the supplementary experiment, single, double, and triple ozonation were compared in relation to starch content, vitamin C concentration, and tuber mineral composition. Fungicide treatment most effectively limited late blight symptoms, particularly at later assessment dates, and was associated with the highest tuber yield. SPAD values, yield, and several mineral traits were strongly dependent on the study year, indicating a major contribution of environmental conditions. The response to O3 and H2O2 was selective and less stable than that observed under fungicide protection. In the supplementary experiment, the number of ozone applications did not significantly affect starch content. Vitamin C concentration depended mainly on the study year, whereas tuber mineral composition depended mainly on year and tissue type. The results indicate that, under field conditions, fungicide protection remained the most effective option for limiting late blight and achieving the highest tuber yield, whereas O3 and H2O2 should be regarded as factors capable of modifying selected plant and tuber traits, but not as direct substitutes for standard chemical protection.