Preservation of Food Sugar Beet via the Control of _Rhizoctonia solani_ AG 2-2 IIIB by Extreme Factors  
[PERSON]  
1 Institute of Environmental Engineering and Biotechnology, University of Opole, 45-040 Opole, Poland; [EMAIL_ADDRESS] (V.H.); [EMAIL_ADDRESS] (O.T.); [EMAIL_ADDRESS] (E.  
agriculture and industry, since it is one of only two plants providing sucrose [7]. It covers about 35% of the global white sugar harvest [9]. Therefore, the project of reducing the impact of _R. solani_ and inhibiting its growth is of great interest to those wishing to prevent the loss of crop yields.  
Different strategies have been developed to fight against this plant pathogen. The cultivation of sugar beet varieties resistant to _R. solani_ is one of the most important among them [10,11]. However, only partially resistant varieties are known. They require additional control and provide lower yields [8]. Suppression of the pathogen in soil is another strategy. Formerly, the application of fungicides was a widespread method. However, their long-term use caused the formation of resistance, as well as pollution of the environment [1,12]. The appearance of new strains frequently caused a loss in the efficiency of existing fungicides [13]. Therefore, other approaches are of great interest. Nowadays, the method of suppression of _R. solani_ growth by microorganisms or by some organic compounds is popular [1,5,8]. For example, _Trichoderma harzianun_ was shown to be antagonistic to _R. solani_ via growth on the mycelium, penetration into cells, and production of chitinase and \(\beta\)-(1,3)-glucanase [12]. Microbial species _Pseudomonas stutzeri_ was reported to inhibit the growth of _R. solani_ via lipase production for the degradation of fungal cell wall lipids [1]. _Bacillus_ sp. was shown to be a commonly used control agent [14]. The application of different organic amendments was also revealed to be promising. The inhibition of _R. solani_, together with plant growth promotion, was shown via the application of compost [5]. Chitin and keratin amendments have been shown to suppress pathogenic fungi [8]. Brassica tissues (mustard oilcake) were also reported to inhibit _R. solani_. The thioglucide compounds that they contain were hydrolyzed to isothiyanates, providing fungi suppression [12]. These methods are promising. However, they are often unpredictable, since there is not enough data to regulate and control the process [8,15,16]. The creation of unfavorable growth conditions for _R. solani_ is the general purpose of each one of these methods. However, they approach the problem in a limited way, considering the interaction of certain compounds or biological control agents with _R. solani_ separately. That is their weakness.  
Several anastomosis groups of _R. solani_ are involved in sugar beet and potato disease, including AG 1 to AG 5. The isolates belonging to AG 2 and AG 4 were identified as the most frequently occurring in sugar beet production, and AG 3 in potato cultivation [17,18]. Crown and root rot, as well as the damping off of sugar beets, are mostly caused by two intraspecific groups of _R. solani_: AG 2-2 IIIB and AG 2-2 IV [17,19,20,21]. AG 2-2 IIIB is more virulent to sugar beets than AG 2-2 IV [19]. Both of these are found worldwide, but AG 2-2 IIIB seems to be more common in Europe, especially in the fields where corn and sugar beets are cultivated alternately [22]. In Europe, more than 36,000 ha are affected by _R. solani_ AG 2-2 IIIB each year [23,24]. The productivity of valuable food plants strongly depends on the control of this phytopathogenic agent.  
Therefore, the goal of the work was to investigate the effect of abiotic factors (pH, Eh, presence or absence of O\({}_{2}\)) and biotic ones (microbial community) on the fungal pathogen _R. solani_ AG 2-2 IIIB for its control and sugar beet protection.