## 3 Results
### Production of VOCs by Calla Lily and by Cabbage in Response to Incoulation of Pectobacterium
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**RT (min)**} & **Identified Volatile Compounds** & **Cabbage Control** & **Cabbage + PC16** & **Cabbage + WPP14** \\ \hline
2.10 & Ethanol & + 1 & + & + \\
2.78 & Ethyl acetate & + & + & + \\
3.65 & 3-Hydroxy-2-butanone & + & + & + \\
3.84 & Isopentyl alcohol & & & + \\
4.0 & Methyl disulfide & & & + \\
4.20 & 4-Methylheptane & + & + & + \\
4.58 & Octane & + & + & + \\
4.88 & 2,4-dimethylheptane & + & + & + \\
5.10 & 2,4-dimethylheptene & + & + & + \\
5.36 & 4-methyloctane & + & + & + \\
7.13 & Branched alkanes & + & + & + \\
7.18 & Branched alkanes & + & + & + \\
7.71 & Dibutoxy-methane & + & + & + \\
7.96 & Branched alkanes & + & & + \\
8.01 & Branched alkanes & + & & + \\
8.26 & Not identified & & & + \\
8.34 & Not identified & & & + \\
9.73 & Not identified & & & + \\
10.09 & 2,6,10,14-tetramethyl & & & + \\  & heptadecane & & & + \\
10.37 & Not identified & & & + \\
11.20 & Not identified & & & + \\ \hline \end{tabular} \({}^{1}\) Sign “+” indicates presence of that compound in the given sample.  
\end{table} 
Table 2: VOCs collected from the headspace of cabbage samples inoculated with PC16 or WPP14 and the corresponding control (DDW), as identified by GC-MS. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**RT (min)**} & **Identified Volatile Compounds** & **Calla lily Control** & **Calla lily + PC16** & **Calla lily + WPP14** \\ \hline
2.36 & Methyl acetate & & + & & \\
2.78 & Ethyl acetate & & + & & \\
3.80 & Isopentyl alcohol & & + & & \\
4.20 & 4-Methylheptane & + 1 & & + & \\
4.25 & Toluene & + & & & \\
4.28 & Isobutyl acetate & & + & & \\
5.09 & 2,4-Dimethyl-1-heptene & + & & + \\
5.38 & 4-Methyloctane & & & + \\
5.51 & Isopentyl acetate & & + & \\
7.13 & Branched alkanes & + & + & + \\
7.18 & Branched alkanes & + & + & + \\
7.70 & Dibutoxy-methane & + & + & + \\
7.96 & Branched alkanes & & & + \\
8.01 & Branched alkanes & & & + \\
10.09 & 2,6,10,14-tetramethyl & + & + & + \\  & heptadecane & & & + \\  & Similar to & & & \\  & sandaracopimaradiene & & & \\ \hline \end{tabular} \({}^{1}\) “-“ indicates presence of that compound in the given sample.  
\end{table} 
Table 3: VOCs collected from the headspace of calls lily samples inoculated with PC16 or WPP14 and the corresponding control (DDW), as identified by GC-MS.  
and 4-methyl heptane in all cabbage samples, respectively. Among these 4 compounds, isopentyl alcohol was specific to cabbage + WPP14 samples. Based on the FID signals, a marked increase in the amounts of ethanol and 4-methyl heptane was observed in cabbage leaves that were inoculated with WPP14. Expression of Defense-related Genes in Calla Lily and Cabbage in Response to Pectobacterium Infection  
Plant immune systems may be activated in response to biotic and abiotic stresses, including a pathogen attack. To better understand the pathways underlying the observed specificity of _Pectobacterium_ strains to their hosts, we tested the expression of marker genes that are related to plant-defense pathways in two hosts: calla lily and cabbage. The expression of the genes for lipoxygenase (_lox2_), phenylalanine ammonia lyase (_pal_), aspartate aminotransferase (_ast_) and a pathogenesis-related gene (_PR-1_) were studied in response to infection with either PC16 or WPP14. In calls lily, all of these genes were significantly upregulated following infection with PC16 or WPP14. However, expression levels were higher following infection with PC16, as compared to WPP14, except for the gene _PR-1_ (Figure 4A). In cabbage, the genes _lox2_ and _PR-1_ were significantly upregulated by both PC16 and WPP14, with greater expression in response to WPP14 infection. The genes _pal_ and _ast_ were only upregulated in response to infection with WPP14 (Figure 4B). Figure 4: Expression of defense-related genes _pal_, _lox2_, _ast_ and _PR-1_ in (**A**) calla lily and (**B**) cabbage following infection with _Pectobacterium_ strains PC16 or WPP14.