# Salicylic Acid Modulates Volatile Organic Compound Profiles During CEVd Infection in Tomato Plants
## 5 Conclusions  
Our findings reveal that CEVd infection induces genotypic and salicylic acid (SA)-dependent changes in the VOC production of tomato plants. SA plays a pivotal role in modulating these responses, with SA-deficient plants (_NahG_) undergoing extensive metabolic reprogramming, whereas SA-accumulating plants (_RNAi_55H_) exhibit a more regulated and targeted defence response.  
Notably, the identification of specific VOCs as differentially regulated across genotypes underscores their potential for the development of VOC-based strategies for sustainable disease management. Moreover, the identification of VOCs associated with viroid symptomatology holds promise for the use of these biomarkers for early detection. These findings provide valuable insights into the intricate metabolic interactions shaping plant-pathogen dynamics and offer promising avenues for enhancing crop resistance through targeted metabolic engineering and breeding strategies.  
**Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/metabo15020102/s1](https://www.mdpi.com/article/10.3390/metabo15020102/s1)]([https://www.mdpi.com/article/10.3390/metabo15020102/s1](https://www.mdpi.com/article/10.3390/metabo15020102/s1)): Supplemental Figure S1: Volcano plots showing differentially expressed volatile organic compounds (VOCs) in _Solanum lycopersicum_ genotypes (wild-type, _NahG_, and _RNAi_55H_) upon Citrus Exocortis Viroid (CEVd) infection compared to mock treatment. Each dot represents a VOC, plotted by its statistical significance (\(-\)log\({}_{10}\)\(p\)-value) against its fold change (log\({}_{2}\)FC). Compounds with high fold changes are positioned toward the sides of each plot, indicating strong over- or under-accumulation in response to CEVd infection. Colours represent the fold-change magnitude, with red indicating high over-accumulation and blue indicating high under-accumulation. Supplemental Table S1. Retention times and characteristic mass values for volatile organic compounds (VOCs) identified in Solanum lycopersicum genotypes. Compound retention time (in minutes) and primary mass-to-charge ratio (m/\(z\)) were determined using gas chromatography-mass spectrometry (GC-MS). Compounds with asterisks (*) indicate tentative identification.  
**Author Contributions:** [PERSON] and [PERSON] performed the experiments. [PERSON] and [PERSON] performed the formal analyses. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] designed the experiments and analyzed and discussed the results. [PERSON], [PERSON] and [PERSON] wrote the original draft. All authors reviewed and edited the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by grants PID2020-116765 RB-I00 and PID2023-152361 OB-I00 funded by MCIN/AEI/10.13039/501100011033/ and supported by grant PROMETEU/2021/056 by Generalitat Valenciana.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available in this article and Supplementary Materials.  
**Acknowledgments:** We would like to thank the IBMCP Metabolomics Platform (Valencia, Spain), especially [PERSON], for her excellent technical support in VOC quantification.  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.