## 3 Results
### Comparative Analysis of the Secondary Metabolite Biosynthesis Gene Clusters and Produced VOCs  
In previous works in our lab, we reported some biosynthesis gene clusters of the four bacterial strains [11, 13, 22]. However, in this work, we decided to perform a new analysis and compared the biosynthesis gene clusters between the four strains [12, 14, 16]. The results are shown in Table 3. The studied strains from the genus _Bacillus_ share gene clusters for petrobactin, bacillibactin, and molybdenum cofactor. _Bacillus toytonsis_ COPE52 also has a gene cluster for bacittacin and paeninodin. The four strains have a gene cluster for fengycin, a nonribosomal peptide synthetase cluster (NRPS), and unspecified ribosomally synthesized and post-translationally modified peptide product (RiPP) cluster. _Pseudomonas fluorescens_ UM270 has a gene cluster for the antibiotic 2,4-diacetyl phloroglucinol, fragin, and serobactin, among others. Figure 1: Biocontrol assay for strawberries and grapes. The top panel shows firmness and disease incidence for strawberries. The bottom panel shows firmness and disease incidence for grapes. The first column of the graphics shows results with _Fusarium brachytigibosum_, the second column with _Botrytis cinerea_, and the third column with _Alternaria alternata_. Bars represent the mean \(\pm\) SE values; letters indicate that the means differed significantly after [PERSON]’s multiple range test (\(p<0.05\)). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Gene Cluster** & \begin{tabular}{c} _Bacillus_ **sp.** \\ **COPE52** \\ \end{tabular} & \begin{tabular}{c} _Bacillus_ **sp. E25** \\ \end{tabular} & \begin{tabular}{c} _B. thuringiensis_ \\ **CR71** \\ \end{tabular} & \begin{tabular}{c} _Pseudomonas_ \\ _fluorescens_ **UM270** \\ \end{tabular} \\ \hline \hline \begin{tabular}{c} Bicittracin \\ \end{tabular} & \(55\%\) & - & - & - \\ \hline \begin{tabular}{c} Petrobactin \\ \end{tabular} & \(100\%\) & \(100\%\) & \(100\%\) & - \\ \hline \begin{tabular}{c} Bacillibactin \\ \end{tabular} & \(46\%\) & \(46\%\) & \(46\%\) & - \\ \hline \begin{tabular}{c} Fengycin \\ \end{tabular} & \(40\%\) & \(40\%\) & \(40\%\) & \(13\%\) \\ \hline \
\begin{tabular}{c} Molybdenum cofactor \\ \end{tabular} & \(17\%\) & \(17\%\) & \(17\%\) & - \\ \hline
\begin{tabular}{c} Paeninodin \\ \end{tabular} & \(80\%\) & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Gene clusters predicted by antiSMASH pipeline by the four PGPR, _Bacillus_ spp., strains COPE52, E25, CR71, and _Pseudomonas fluorescens_ strain UM270. Volatile organic compounds (VOCs) of the plant-growth-promoting bacterial strains are shown in Table 4. The four strains can produce dimethyl disulfide, which has been reported to exhibit antimicrobial activity. _P. fluorescens_ UM270 produces several other sulfur compounds and dimethylhexadecilamide, a compound that promotes plant growth and has antifungal activity [24]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Volatile Compound**} & **UM270** & **E25** & **CR71** & **COPE52** \\ \cline{2-5}  & **\%** & **\%** & **\%** & **\%** \\ \hline Methanethiol & 15.13 & n.d. & n.d. & n.d. \\ \hline Dimethyl sulfide & 23.4 & n.d. & n.d. & n.d. \\ \hline
2-Butanone & n.d. & 2.32 & 2.24 & 0.99 \\ \hline
1-Nonene & 2.02 & n.d. & n.d. & n.d. \\ \hline Methyl thiolacetate & 1.17 & n.d. & n.d. & n.d. \\ \hline Dimethyl disulfide & 5.62 & 2.11 & 2.65 & 2.63 \\ \hline
1-Decene & 0.53 & n.d. & n.d. & n.d. \\ \hline
1-Undecanol & 50.01 & n.d. & n.d. & n.d. \\ \hline
2,4-Dithaipentane & n.d. & n.d. & n.d. & n.d. \\ \hline
1-Dodecene & n.d. & n.d. & n.d. & n.d. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the VOCs produced by the four bacterial strains, _Bacillus_ spp., strains COPE52, E25, CR71, and _Pseudomonas fluorescens_ strain UM270.