## 1 Introduction
Regardless of the geographical distribution, _R. solani_ is an important pathogen of potatoes and other root vegetables [27; 28; 29; 30; 31; 32; 33]. The level of losses caused during potato cultivation depends on the severity and time of the plant infection. What is dangerous is the rotting of shoots, which occurs during the emergence. On the other hand, later infections affect potato tubers (black scurf). Black hardened fungal hyphae (sclerotic) contaminate the perioderm of potato tubers, contributing to the deterioration of quality. Severe infection is often accompanied by the diminution of tubers, which may disqualify their suitability for processing. Furthermore, sclerotia are the source of infection in the next growing season, and spores that form in the soil do not lose their ability to infect for several years [34; 35]. According to [PERSON] et al. [36], potato is the only host for the fungus _Helminthosporium solani_. Silver scurf, a disease caused by this fungus, is relatively common, but symptoms on unwashed tubers may remain unnoticed. Hyphae of the fungus _H. solani_ spread between cells and in cells, forming an air space under the perioderm of the tubers [37]. The result of the infection includes extensive stains with silver gloss. Water is lost through the damaged skin during storage, the tubers shrink, and the loss of mass may reach 17% [16; 38; 39]. An important factor in reducing the disease severity is to ensure adequate sanitary conditions and to reduce inoculum near the tubers by removing crop and soil residues [13]. However, planting infested potato tubers is the main source of _H. solani_ in the soil. The presented disease units are caused by unrelated phytopathogens with varying life cycles, range of hosts, and different symptoms that can be present on the same potato tubers at the same time. Knowledge of the causes of diseases is crucial for the successful management of potato production. In practice, the fight against pathogens living in soil and carried with seed potatoes is not easy [20; 21; 30; 32; 40; 41; 42; 43; 44]. It should be highlighted that the use of chemical protective agents may be ineffective if environmental conditions promote the dispersion of pathogens or if fungicide-resistant genotypes appear [45; 46; 47]. The use of synthetic pesticides has numerous times been shown to lead to a loss of soil biodiversity and an accumulation of pathogenic bacteria, fungus-like organisms, and fungi in soil [42; 43; 44; 48]. The introduction of organic matter to soil is one of the more effective methods of restoring soil biodiversity and balance between populations of beneficial and pathogenic microorganisms [49; 50; 42]. Different types of microbiological preparations, effective microorganisms, and soil conditioners can play a similar role [51; 52]. Many authors point out that their use in the cultivation of different plant species has had a positive effect on the yield, the content of nutrients, and bioactive substances [53; 54; 55; 56; 57]. In addition, they have increased plant resistance processes against biotic factors resulting in better plant health [58; 32]. Due to the concern of protecting biodiversity, the environment, and the consumer, biological preparations applied to soil and onto plants will supplant chemical plant protection products. In line with these requirements and increasing health standards for potato tubers, six preparations that are authorized for use in organic potato production systems were tested. The aim of this study was to (I) determine the extent to which the soaking of healthy seed potatoes in the following solutions: biological control agents (BCAs) (Polyversum WP, Serenade ASO), plant growth promoters (PGPs) (Kelpak SL), and microbiological soil additives (MSADs) (Em FarmaTM, UGMax soil conditioner, Biogen Rewital), as well as their introduction into the soil just before potato planting, shape the health of the surface of the tubers and the total yield of the potato.