## 4 Discussion  
Vascular wilts are devastating plant diseases that cause major economic losses in strawberry production globally. The present work aims to address this issue by isolating potential bacterial antagonists that can be integrated into disease management strategies. In this study, 73 strains of bacteria were isolated from maize straw compost tea and screened for their ability to produce VOCs with antifungal activity against _V. dahliae_ and FOF. One of the most effective isolates, designated as CT32, was identified as _B. velezensis_. Members of the species _B. velezensis_ are well known for their ability to promote plant growth and to synthesize of a diverse array of secondary metabolites, such as bacillomycin D, plantazolicin and amylocyclicin, that can inhibit the growth of plant pathogens [25; 26; 27; 28]. Our results provide evidence that VOC production can play an essential role in the biocontrol activity of _B. velezensis_ CT32 against vascular wilt pathogens. A broad-spectrum antifungal effect was exhibited by VOCs emitted by strain CT32, even though the inhibition rate was low for some pathogenic fungi. The experimental data revealed that the extent of inhibition varied greatly depending on the fungal species. This is consistent with the results obtained by [PERSON] et al. [29], who reported that the volatiles from _Lysinibacillus_ sp. FJAT-4748 did not affect the growth of all pathogenic fungi to the same extent. The observed differences in fungal susceptibilities to bacterial VOCs may be explained by differences in the action site or in the ability of fungal pathogens to detoxify the volatiles [30]. In addition, considering that different isolates of each pathogen type vary in terms of their physiological properties and pathogenicity, the inhibitory effect on one pathogen isolate observed in our study may not represent the responses of all isolates of the species to bacterial volatiles. Notably, the VOCs produced by strain CT32 were particularly active in inhibiting the mycelial growth of _V. dahliae_ and _F. oxysporum_. Similarly, previous studies have reported the in vitro growth inhibition of tomato vascular wilt pathogens by VOCs released from _Bacillus_ spp. ; however, they did not identify the bioactive compounds responsible for the inhibition [31; 32]. To identify the volatile compounds composing the natural emissions of strain CT32, HS-SPME-GC-MS was employed. In comparison with other sampling techniques, HS-SPME allows the volatile metabolites in the headspace of the bacterial cultures to be preconcentrated prior to analysis by GC-MS [33]. In fact, HS-SPME-GC-MS has been used for profiling VOCs from various microbial samples without contaminating the culture or causing damage to living cells [34; 35; 36]. The results of this study show that the volatile blend produced by strain CT32 comprised 30 individual compounds. To the best of our knowledge, six of the 30 identified volatiles have not previously been reported to be produced by bacteria or fungi: (Z)-5-undecene, decyl formate, 2,4-dimethyl-6-tert-butylphenol, dodecanentirile, 2-methylpentadecane and 2,2',5,5'-tetramethyl-1,1'-biphenyl. The predominant classes of compounds detected in the headspace of strain CT32 were alkanes, ketones, alcohols, and aldehydes. However, [PERSON] et al. [31] reported that terpen, alcohols, and alkanes were the major classes of compounds released from the endophytic _B. velezensis_ strain C2. This discrepancy may be explained by the different methods applied to collect and detect VOCs. It needs to be recognized that bacterial VOC profiles are greatly influenced by the sample preparation method as well as the extraction and chromatographic procedures, such as the choice of culture media, duration of incubation, choice of capillary column and selection of SPME fibres, all of which can lead to inconsistent results and hinder the comparison between different studies.