## 2 Results and Discussion  
Potato pathogens can lead to significant losses in storage. Infections occur via wounds that result from harvesting in non-optimal storage conditions. Effective control of potato pathogens during storage requires rapid and accurate tools for diagnosis, and earlier diagnostics may result in better management. In this work, we visually assessed the symptoms of potato pathogens infections caused by both bacterial and fungal pathogens. Then, HS-SPME-GC-MS was used to detect volatile organic compounds produced by these pathogens. PCA and hierarchical cluster analysis were performed. Markers in the form of VOC were proposed for general potato infection and for each pathogen. Afterward, the selected growth parameters were determined under greenhouse conditions. Visual inspection has been a common method to identify disease symptoms. The visual assessment of the potato infestation with pathogens is summarized in Table 1.  
A variety of fungal and bacterial phytopathogens can cause severe potato diseases during storage. _Fusarium_ species are the most common fungal pathogens that attack potatoes. They are responsible for dry rot, characterized by wrinkled and sunken brown or black tissue parts as well as cottony white or purple mycelial and spore pads concentrically arranged on the potato tuber surface [35; 36]. Similar symptoms were observed in our research for _F. sambucinum_ and _F. oxysporum_. Their growth was visible as white, wadded mycelial and spore pads on the tubers, which partially collapsed (Table 1). Other fungal pathogens of potatoes are _Alternaria_ species, the cause of early blight. This disease manifests as sunken, dark lesions on the tuber surface [37]. In the present work, _A. tenuissima_ caused the most substantial infectious changes among the three tested _Alternaria_ strains (Table 1). White and light brown, lumpy mycelial and spore pads were observed on the whole surface of the potato and the tubers were also sunken. _A. alternata_ and _A. solani_ induced only poorly visible white mycelial spots on the potato tubers. The symptoms of _Phoma exigua_, the cause of gangrene, are most often described as sunken, thumbprint-like lesions on the potato surface. Inside the tuber, dark rot develops [38]. In our experiments, a rotting and lumpy mass was observed inside the potato tubers (Table 1). Black scurf is another fungal disease of potato, caused by _Rhizoctonia solani_, and dry ulcer rot is the most common symptom of this disease [39]. Foaming, decaying mass inside and slightly visible white, wadded mycelium on the tuber surface was noted in our work (Table 1). In addition,Colletotrichum cococodes_ (black dot disease) can infect potato tubers during storage. The crop damage caused by this pathogen is increasing. The symptoms of infestation include silvery lesions on the tuber surface and the presence of black microsclerotia [9]. In our research, however, potatoes infected with _C. cococodes_ did not reflect the literature description. This pathogen-induced tuber decay, formed a soft mass, clearly separated from the skin (Table 1). Differences between the laboratory method and naturally occurring way of pathogen inoculation may be the reason for this. One of the most serious bacterial diseases of potato is soft rot, caused by _Pectobacterium carotovorum_. Sunken lesions and decayed inside of the tuber are reported as the main symptoms of this disease [40], and the same tuber changes were observed in our experiments. A cream-colored, soft mass with a characteristic smell occurred after incubation of tubers infected with _P. carootovorum_ (Table 1). This bacterium (as well as _Pectobacterium versatile_ and _Pectobacterium atrosepticum_) is also responsible for blackleg disease that causes wilting of the whole plant, and blackening and necrosis of the stem [41]. Another significant bacterial pathogen of potato is _Streptomyces scabiei_, the cause of common scab. This disease manifests as a pitted, erumpent, or mild netted scab of potato tuber [40].