# Salicylic Acid Modulates Volatile Organic Compound Profiles During CEVd Infection in Tomato Plants
## 3 Results
### Salicylic Acid Accumulation Modulate Volatile Profile in CEVd-Infected Tomato Plants  
To further investigate the specific metabolites contributing to the distinct metabolic shifts observed in the PCA, a volcano plot analysis was conducted to identify differentially accumulated VOCs between CEVd-infected and mock-treated plants across the _NahG_, _RNAi_SSH_, and wild-type genotypes (Supplemental Figure S1). This analysis enabled the visualization of VOCs that were statistically up- or down-accumulated in response to CEVd infection in each genotype, based on both fold change (FC) and statistical significance (\(p\)-value). The volcano plot analysis (Figure S1A) identified specific volatiles significantly accumulated in CEVd-infected 'MoneyMaker' tomato plants, with a log 2 FC (CEVd infected/mock) \(\geq\) 1 and \(\leq\)-1. Among these, an aldehyde derived from fatty acids such as (E)-2-octenal, the monoterpene derivative \(p\)-cymene, and various benzenoids, including guaiacol and methyl salicate (MeSA), were identified (Table 1). In addition, the accumulation of some VOCs decreased upon CEVd infection, including the monoterpenoids linalool and (Z)-2-caren-4-ol, and the organic compound malonamic acid. All compounds were unequivocally identified by comparison with pure standards, except for three VOCs (malonamic acid, (Z)-2-caren-4-ol, and (_E,E_)-Cosmene), which were tentatively assigned based on their high degree of mass spectral scores (match score > 900). To identify and cluster the compounds associated with plant response to CEVd infection in the three genotypes, a heatmap analysis was conducted (Figure 3). This analysis illustrated the differential accumulation of VOCs across the three genotypes (_NahG_, _RNAi_SSH_, \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Compound** & \begin{tabular}{l} **Family** \\ **Code/Number** \\ \end{tabular} & \begin{tabular}{l} **Retention Time** \\ **(min)** \\ \end{tabular} & \
\begin{tabular}{l} **Specific Ion (\(m/z\))** \\ \end{tabular} &
\begin{tabular}{l} **Log 2** \\ **(CEVd/Mock)** \\ \end{tabular} \\ \hline Malonamic acid 1  & Acid/1 & 7.98 & 43 & \(-\)1.72 \\ (_Z_)-2-Caren-4-ol 1  & \(\text{Alc}/1\) & 24.58 & 107 & \(-\)2.56 \\ -P-Cymene & Mt hd/1 & 24.75 & 119 & 1.69 \\ (_E_)-Cosmene 1  & Mt hd/2 & 24.79 & 98 & \(-\)1.48 \\ (_E_)-2-Octenal & Ald/3 & 25.62 & 83 & 1.25 \\ Guaiacol 2  & Alc/4 & 26.82 & 59 & 1.06 \\ Lindalool 1  & Alc/5 & 26.99 & 93 & \(-\)3.83 \\ Methyl salicate 2  & Est/1 & 30.57 & 65 & 1.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of differentially accumulated VOCs in CEVd-infected MoneyMaker tomato leaves. and wild type). The clustering patterns revealed genotype-specific VOC profiles, providing valuable insights into the metabolic pathways either activated or suppressed in response to CEVd infection, highlighting their potential roles in tolerance and susceptibility. The volcano plot analysis for CEVd-infected _NahG_ tomato plants compared to mock-inoculated wild-type plants (Figure S1B) revealed several volatiles that were statistically over-accumulated in these susceptible plants (green colours in column 1 of Figure 3). This so-called \"aroma of death\" included a diverse range of VOCs including methane monoterpenes such as D-limonene and terpinolene; ment  
Figure 3: Hierarchical cluster heatmap of the VOCs in CEVd-infected tomato plants across genotypes. The log2-transformed ratios are represented as a heatmap according to the scale below. Red corresponds to higher values; green denotes lower values. Column 1 represents the ratios of the VOCs accumulated by CEVd-infected _NahG_ tomato plants versus the mock-inoculated plants. Column 2 represents the ratios of the VOCs accumulated by CEVd-infected WT tomato plants versus the mock-inoculated plants. Column 3 represents the ratios of the VOCs accumulated by CEVd-infected _RNAi_SSH_ tomato plants versus the mock-inoculated plants. * Tentative identification based on mass spectrum.