## 4 Discussion
### Chemical Compounds Detected by GC-Ms
[20] identified 3-chloro-4-methyloxybenzaldehyde in _F. oxysporum_, which was also confirmed by our results (Table 2). In addition, both the results of [PERSON] et al. [20] and our results indicate the presence of numerous chlorobenzene derivatives in _F. oxysporum_ cultures (Table 2). It should be noted that a large amount of information on volatile organic compounds produced by pure _Bacillus_ cultures is available in the literature [23; 25; 30; 40; 41; 43; 47; 48; 49; 52]. In contrast, literature data on volatiles emitted by fungi of the genus _Fusarium_ are far less extensive [20; 30], and information on volatile compounds produced during the interaction between bacteria of the genus _Bacillus_ and fungi of the genus _Fusarium_ is relatively scarce [30]. [PERSON] et al. [30] found the presence of 14.56 \(\pm\) 4.17% isopentanol in the composition of volatiles obtained from the interaction of _Bacillus_ sp. LPPC170 and _F. oxysporum kalimantanense_ LPPC130, while our results confirmed a 0.22 \(\pm\) 0.01% content of this alcohol released during the interaction of _B. amyloliquefaciens_ and _F. oxysporum_ (Table 3). [PERSON] et al. [30] also identified butane-2,3-diol (0.05 \(\pm\) 0.10%) during the interaction of _Bacillus_ sp. LPPC170 and _F. oxysporum kalimantanense_ LPPC130, which was confirmed by our results indicating 0.26 \(\pm\) 0.03% concentration of this diol produced during the interaction of _B. amyloliquefaciens_ and _F. oxysporum_ (Table 3). It is also worth noting that, based on our analyses, butane-2,3-diol was present during the interaction of _B. amyloliquefaciens_ and _F. oxysporum_, whereas it was not found in pure _B. amyloliquefaciens_ and _F. oxysporum_ cultures (Table 3). Other groups of compounds produced during the interaction of _Bacillus_ bacteria and _Fusarium_ fungi are ketones and carboxylic acids. [PERSON] et al. [30] found nonan-2-one (\(0.08\pm 0.01\%\)) in the interaction of _Bacillus_ sp. LPPC170 and _F. oxysporum kalimantanense_ LPPC130, and the presence of this ketone in the interaction of _B. amyloliquefaciens_ and _F. oxysporum_ (1.46 \(\pm\) 0.11%) was also confirmed by our results (Table 3). [PERSON] et al. [30] found that the interaction of _Bacillus_ sp. LPPC170 and _F. oxysporum_ kalimantanense_ LPPC130 showed an acetic acid content of 0.38 \(\pm\) 0.12%, while our analyses showed a very similar acetic acid content (0.37 \(\pm\) 0.01%) in the interaction of _B. amyloliquefaciens_ and _F. oxysporum_ (Table 3). In addition, [PERSON] et al. [30] identified an anisole during the interaction studies of _Bacillus_ sp. LPPC170 and _F. oxysporum_ kalimantanense_ LPPC130, and our work confirmed the occurrence of anisole derivatives during the interactions of _B. amyloliquefaciens_ and _F. oxysporum_ (Table 3). [PERSON] et al. [30] concluded that _Bacillus_ sp. LPPC170 and _F. oxysporum kalimantanense_ LPPC130 interacted with each other via volatiles, leading to changes in the metabolism of both microorganisms. When the bacteria and the fungus interact, the production of some microbial VOCs can be increased, while other compounds can be produced in reduced quantities [30; 54]. The same observations also emerged after a detailed analysis of the chemical composition of both pure _Bacillus_ cultures and _F. oxysporum_ fungi and the VOC compositions emitted during bacterial-fungal interactions (Table 3). The use of individual pure volatile compounds to control _Fusarium_ fungi is also interesting. The compounds used in such studies are identified by HS-SPME/GC-MS in the volatile emission of pure bacterial cultures of the genus _Bacillus_. Commercial standards of the identified compounds are then used in the studies, and the effect of a particular compound on the growth of a particular _Fusarium_ fungus species is tested. Thus, by determining the degree of inhibition (%) in the antagonism test, the effect of a specific, single chemical compound is determined and not that of a mixture of volatile organic compounds produced by _Bacillus_ bacteria. [PERSON] et al.