## 4 Discussion  
Postharvest fruit has a certain shelf life and undergoes a normal process of deterioration or decay due to respiration, ethylene production, the presence of fungi, and storage conditions (humidity, temperature, atmosphere, etc.). During this process, the fruit loses weight and firmness, and quality decreases. The main postharvest pathogens of a variety of fruits and vegetables have been reported to be the genera _Apergillus_, _Botrytis_, _Fusarium_, _Geotrichum_, _Gloesporium_, _Monilia_, _Mucor_, _Penicillium_, _Alternaria_, and _Rhizopus_[2]. _Botrytis_, _Fusarium_, and _Alternaria_ are frequently found and are the major causative agents of postharvest disease in berries [25; 26; 27; 28; 29; 30; 31; 32]. In a previous work, we isolated 20 fungi from berries in postharvest decay [17]. These isolates were characterized to belong mainly to the genera _Botrytis_, _Fusarium_, _Geotrichum_, _Mucor_, _Penicillium_, and _Alternaria_, which belong to the most common postharvest pathogens in fruits and vegetables [2]. In this work, we performed antagonistic essays against these postharvest fungal pathogens using four different plant-growth-promoting bacterial strains. We also selected three fungal pathogens (_Fusarium brachygibbsum_ 4 BF, _Botrytis cinerea_ 62 BCV, and _Alternaria alternata_ 1A) to evaluate the bacterial strains for their biocontrol potential against the pathogens on strawberry and grape fruits. PGPB can be used to prevent fungal pathogen growth via their biocontrol properties [21]. [PERSON] et al., 2023 [33] evaluated the biocontrol and plant-growth-promoting activities of two distinct _Bacillus haltolerans_ strains (Cal.130 and Cal.f.4). The application of the two strains individually and as a mixture significantly enhanced the growth parameters of _Arabidopsis_ and tomato plants. The two strains also significantly inhibited the growth of _Botrytis cinerea_. In a previous work, the authors isolated the strain Cal.1.30 from the medicinal plant _Calendula officinalis_, and it was selected for its strong biological potential against _Botrytis cinerea_. The _Bacillus haltolerans_ strain and its cell-free supernatant reduce the gray mold disease severity index and disease incidence on harvested grapes and cherry tomato fruits. It has also been shown via HPLC-HRMS analysis that this strain synthesizes and secretes metabolites with antimicrobial activity, including the lipopeptides fengycin, surfactin, and mojavensin A, bacillaene isoforms, L-dihydroanticapsin, and bacillibactin, among others [20]. In Ref. [19] in this study, beneficial bacilli and pseudomonad strains showed significant percentages of mycelial growth inhibition against these previously characterized pathogens. Regarding the results of inhibition in vitro by diffusible and volatile compounds, it was observed that the inhibition of several isolates was greater by diffusible compounds than by volatile organic compounds. A probable explanation for this result could be that the compounds produced by bacteria that diffuse in the medium affect the growth of the fungus more directly since they are in direct contact with the vegetative mycelium, and perhaps harm the fungus in its ability to acquire nutrients and develop. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Volatile Compound**} & **UM270** & **E25** & **CR71** & **COPE52** \\ \cline{2-5}  & **\%** & **\%** & **\%** & **\%** \\ \hline S-Methyl1-methylbutanetthioate & n.d. & n.d. & n.d. & 7.84 \\ \hline
3-Hydroxy-2-butanone & n.d. & n.d. & n.d. & 3.49 \\ \hline Ethyl 3-hydroxybutanoate & n.d. & n.d. & n.d. & 16.21 \\ \hline Propanoic acid & n.d. & n.d. & n.d. & 0.97 \\ \hline
2,3-Butanediol & n.d. & n.d. & n.d. & 2.61 \\ \hline Menthol & n.d. & n.d. & n.d. & 0.78 \\ \hline Ethyl phenylacetate & n.d. & n.d. & n.d. & 1.44 \\ \hline Butyl butanoate & n.d. & n.d. & n.d. & 0.33 \\ \hline \hline \end{tabular} Analysis of volatile organic compounds produced by UM270, E25, CR71, and COPE52 strains, detected by GC/MS analysis (n.d. means not detected).  
\end{table}