## 3 Results
### Assessment of the Effect of Potato Tuber Skin Diseases on Total Yield  
The statistical analysis showed that there is a significant negative correlation between the increase in three diseases of the potato tuber skin and the total yield (Table 8). This applies to black scurf (_R. solani_), common scab (_S. scabies_), and silver scurf (_H. solani_). The preparations used affected the level of these correlations, as indicated by the values of these factors.  
Significant dependencies between DSI for all disease units and yield were observed only in the treatment with BCAP_o_. In contrast, the BCABs treatment and the control had important dependencies for common scab and silver scab. Insignificant relationships between tuber infection by individual pathogens and tuber yield were found in the treatments where EM, UG, BR, and PGPE_m_ were applied. There was also a negligible relationship between the total DSI and the total yield in the PGPE_m_ treatment. Of the analyzed diseases of potato tubers, black scurf correlates negatively with the yield to a lesser extent than other diseases. The correlation coefficients take very low values (Table 8). Only in combination with BCAP_o_ preparation is this interaction at a very high level, i.e., 0.82.  
Apart from one case (PGPE_m_), the total DSI effect of the infection of the potato tubers by pathogens was significantly correlated with the total yield. The regression analysis carried out allowed determining the effect of the cumulative infection of the tuber surface by pathogens on the total yield of the potato tubers (Figure 6). The total DSI proved to be a very useful predictor in estimating the total yield of potato tubers.  
The total DSI correlated the most with yielding in the BCAP_o_ treatment and control, and the determination factors indicated that, respectively, 97.9% and 92.3% of yield variability is explained by the estimated regression equation (Figure 6). In these treatments, an increase of 1% in the total DSI of the potato tuber surface resulted in a decrease in yield by 0.13 and 0.249 t\(\cdot\)ha\({}^{-1}\). In the BCAB_s_, EM, and BR treatments, regression models explain 89.7-85.0% of the variation of the total yield from the total DSI. Any 1% increase in the total severity of potato skin diseases corresponds with a decrease in yield between 0.14 and 0.56 t\(\cdot\)ha\({}^{-1}\).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Specification**} & \multicolumn{3}{c}{**Disease Severity Index—Crop**} & \multicolumn{2}{c}{**Summary**} \\ \cline{2-5}  & **Black Scurf** & **Common Scab** & **Silver Scurf** & **Disease Severity Index—Crop** \\ \hline C & \(-\)0.18 & \(-\)0.78 ** & \(-\)0.68 * & \(-\)0.96 *** \\ BCAP_o_* & \(-\)0.82 *** & \(-\)0.92 *** & \(-\)0.94 *** & \(-\)0.99 *** \\ BCAB_s_ & \(-\)0.46 & \(-\)0.89 *** & \(-\)0.86 *** & \(-\)0.95 *** \\ PGPE_m_ & 0.03 & \(-\)0.53 & \(-\)0.45 & \(-\)0.35 \\ EM & 0.14 & \(-\)0.53 & \(-\)0.48 & \(-\)0.90 *** \\ UG & \(-\)0.18 & \(-\)0.41 & \(-\)0.23 & \(-\)0.83 *** \\ BR & \(-\)0.39 & \(-\)0.53 & \(-\)0.47 & \(-\)0.92 *** \\ \hline \hline \end{tabular}
* * Significant at \(p<0.05\); ** significant at \(p<0.01\); *** significant at \(p<0.001\).  
\end{table}
Table 8: Correlations between the individual and summary severity of potato peel diseases and the total yield.