## 3 Results
### Application of Abiotic Factors for Control of Rhizoctonia solani AG 2-2 IIIB
#### 3.2.2 Effect of Eh and Presence of O\({}_{2}\) on the Growth of Rhizoctonia solani AG 2-2 IIIB  
Aerobic conditions were shown to provide the effective growth of _R. solani_ AG 2-2 IIIB. Under such conditions, the growth of mycelium was active, resulting in a length of 29.3 \(\pm\) 1.2 mm after 6 days of cultivation (Figure 3). The pH value ranged from 6.8 to 7.2. Eh slightly decreased from +255 mV to +238 mV. Thus, there was no inhibition of Rhizoctonia growth.  
The investigation of growth showed its inhibition under anoxygenic and anaerobic conditions. Very little mycelium growth under anoxygenic conditions was observed after only 6 days (1.7 \(\pm\) 1.5 mm). The pH was similar under anoxygenic conditions and ranged from 6.7 to 7.1, but Eh reduced from +126 mV to +103 mV. Such conditions inhibited growth. Complete absence of mycelium growth came about under anaerobic conditions. In this case, the pH was 6.8-7.1. Eh remained at \(-200\)\(\pm\) 10 mV providing unfavorable conditions for _R. solani_ AG 2-2 IIIB. Thus, the presence of oxygen is necessary for _R. solani_ AG 2-2 IIIB growth. It provides high redox potential of the medium. Together, these factors maintained  
Figure 2: Effect of pH on _Rhizoctonia solani_ AG 2-2 IIIB growth: maintenance of pH = 5.5 (black line); maintenance of pH = 7.0 (red line); maintenance of pH = 8.5 (blue line); no pH maintenance (pink line).  
the metabolic activity of the fungus. The absence of oxygen and low redox potential did not support the growth of the fungus.  
2.3 Recovery of _Rhizoctonia solani_ AG 2-2 IIIB Growth after Unfavorable Anoxygenic and Anaerobic Cultivation Conditions  
Cultivation conditions affect the efficiency of growth. Aerobic conditions were shown to support the growth of _R. solani_ AG 2-2 IIIB. On the other hand, slight growth was observed in the case of anoxygenic conditions, and its absence was visualized in anaerobic ones. However, to test whether such conditions cause growth inhibition or death of _R. solani_ AG 2-2 IIIB, the inoculated agar blocks were transferred from anoxygenic and anaerobic conditions to the fresh peptone broth, and cultivation took place in aerobic conditions. Therefore, it was necessary to evaluate it after unfavorable growth conditions.  
The following results were obtained. The recovery of the active fungus growth was predictable in aerobic conditions since the slight growth of mycelium was observed under anoxygenic ones. The length of mycelium was 6.7 \(\pm\) 0.3 mm after one day of cultivation. One week of cultivation resulted in obtaining mycelium of 38.3 \(\pm\) 2.1 mm in length. Thus, anoxygenic conditions can be concluded to cause only the suppression, but not the death of _R. solani_ AG 2-2 IIIB. After the resumption of optimal conditions, growth was recovered. However, the death of mycelium was evidenced in the case of pre-cultivation under anaerobic conditions. The recovery of growth was absent. Thus, creation of strict anaerobic low-potential conditions provided the death of fungal mycelium. Such an approach can be used to control its growth. Since the creation of such conditions via chemical and physical methods is complicated, microbiological methods are considered to be more promising.