## 5 Conclusions  
In conclusion, this study demonstrated a significant plant-growth-promoting effect of _P. putida_ SJ46 and SJ04 VOCs on _M. piperita_ under severe salt stress conditions. In addition, mVOCs emitted by both _P. putida_ showed antagonism against the phytopathogen _A. alternata_ under control and salt conditions, but only against _S. rolfsii_ under control conditions. Through headspace sampling and GC-MS analyses, the mVOCs from both strains were found to be similar, but with the characteristic that the SJ04 strain emitted two compounds not found in the SJ46 blend. Salinity did not modify the compounds emitted by either strain. Moreover, our findings showed for the first time the differential effects of mVOCs emitted by rhizobacteria grown under different salt stress conditions, which may provide an effective approach for the development of microbial resources to help protect plants from salt stress conditions. However, further investigations on mVOC release by PGPR under salt stress conditions should now be carried out to try to elucidate the mode of action of specific compounds or mixtures that can regulate plant physiological processes and lead to salt stress tolerance as well as the control of _A. alternata_ phytopathogens under these conditions. It is also necessary to consider performing future studies on technological improvements for bacterial VOC applications under greenhouse and open field conditions.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/plants12071488/s1](https://www.mdpi.com/article/10.3390/plants12071488/s1)]([https://www.mdpi.com/article/10.3390/plants12071488/s1](https://www.mdpi.com/article/10.3390/plants12071488/s1)): Figure S1: Chromatograms of mVOCs produced by control media (not inoculated) under (a) 0, (b) 75 and, (c) 100 mM NaCl. Figure S2: Chromatograms of mVOCs produced by _E. coli_ DH5\(\alpha\) under (a) 0, (b) 75, and (c) 100 mM NaCl. Figure S3: Chromatograms of mVOCs produced by _P. putida_ SJ46 under (a) 0, (b) 75, and (c) 100 mM NaCl. Figure S4: Chromatograms of mVOCs produced by _P. putida_ SJ04 under (a) 0, (b) 75, and (c) 100 mM NaCl.  
Conceptualization, E.B.; methodology, L.d.R.C., S.S.G. and E.B.; validation, S.S.G. and E.B.; formal analysis, E.B.; investigation, S.S.G. and L.d.R.C.; resources, W.G. and E.B.; data curation, S.S.G.; writing--original draft preparation, S.S.G.; writing--review and editing, E.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Secretaria de Ciencia y Tecnica de la Universidad Nacional de Rio Cuarto, Grant Number PPI 2020-2022: C529-1, the Consejo Nacional de Investigaciones Cientificas y Tecnica (Conicet), the Agencia Nacional de Promocion Cientifica y Tecnologica (Ampcyt), and the Alexander Von Humboldt Foundation.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
This research was supported by grants from the Secretaria de Ciencia y Tecnica de la Universidad Nacional de Rio Cuarto, Consejo Nacional de Investigaciones Cientificas y Tecnica (CONICET), Agencia Nacional de Promocion Cientifica y Tecnologica (ANPCyT), and Alexander von Humboldt Foundation. [PERSON], [PERSON] and [PERSON] are Career Members of CONICET, and [PERSON] has a fellowship from CONICET. The authors are grateful to [PERSON], a native speaker, for editorial assistance.  
The authors declare no conflict of interest.