## 2 Results and Discussion
Small, brown scabs were also observed in our experiments (Table 1). However, such disease symptoms may not be visualized until the infection has progressed significantly, and it is often too late to implement disease mitigation measures. In addition, there could be discrepancies and subjectivity involved in human inspections. Furthermore, visual approaches may be destructive and render limited sampling accuracies [42]. As the result of data analysis obtained from HS-SPME-GC-MS measurements, a total of 130 compounds were identified. The detailed results of these findings are summarized in Table S1. The results were expressed as means of peak area % from duplicate analysis of each sample. The relationships among different phytopathogens used to contaminate potato tubers and volatile compounds after 14 days of storage were determined using a PCA analysis. The principal component analysis (PCA) was carried out using the relative content (% peak area) of volatile compounds as variables. A double criterion was applied to estimate the number of PCA factors that significantly affect the total variance: the own value chart and own values > 1. Using the above criteria, the four PC factors were identified, which explained 67.26% of the total variance. The scatter score plot of principal components (Figure 1) showed the distinction between contaminated samples and the relationship between phytopathogens and volatile compounds determined after 14-day potato storage. The first two factors (PC1 and PC2) accounted for 41.28% of the total variance. The first component (PC1) was characterized by 37 compounds, mainly alkanes. The second factor (PC2) was characterized by 31 compounds mostly including terpen (i.e. \(\alpha\)-cubebeene, D-limonene, \(\alpha\)-guaiene, spiro[3.4]octan-5-one, 3-carene, and chamigrene). Moreover, some alcohols (3-octanol and 3-methyl-1-butanol) and alkanes (1-methyl-4-propylbenzene, 1,2,4-trimethylbenzene, and methylbenzene), as well as dimethyl disulfide, showed high values in the second component. The last components (PC3 and PC4) were both characterized by 20 compounds. The third component accounted for about 14% of the total variance and correlated mainly with 1-butanol, 2-butanone, benzaldehyde, ethyl acetate, propylbenzene, isopropyl benzene, and undecane, whereas the fourth component accounted for 11.98% of the total variance and was related mainly to \(\beta\)-cedrene, 1-octen-3-ol, 2-nonen-1-ol, benzothiazole, and isobutylbenzene. Moreover, during data analysis, the observations were classified based on their correlation to each PC factor (Table 2). The PCA was able to separate samples in the function of phytopathogens used for contamination. The PC1 factor is associated with three samples inoculated with _Alternaria solani_, _Fusarium oxysporum_, and _Rhizoctonia solani_ strains; although, the _Fusarium oxysporum_ strain shows the strongest relationship. Likewise, factors PC2 and PC4 are related to the three trials while the stronger relationship can be linked to the samples inoculated with _Fusarium sambucinum_ and _Alternaria tenuissima_ strains, respectively. In turn, the third factor (PC3) is related only to the control sample. The hierarchical cluster analysis was also applied to evaluate similarities between volatile compounds emitted from potato tuber samples contaminated with different phytopathogens. According to data presented in Figure 2, HCA divided samples into five groups. Groupings were made by using [PERSON]'s method and squared Euclidean distance. The first cluster was represented only by the control sample, while the second cluster, in turn, contained seven samples contaminated with _A. alternata, A. solani, C. cocodes, P. carootororum, P. exigua, R. solani,_ and _S. scabiei_. The profile of these samples was dominated by 3-methyl-1-butanol, 2-methyl-1-butanol, D-limonene, \(\alpha\)-pinene, \(\beta\)-pinene, acetic acid, 3-carene, p-cyclrene, heptanal, octanal, decanal, 3-methylbutanal, 2-methylbutanal, eucalypt, 2-phenylisopropanol, and dibenzofurane.