A targeted and an untargeted metabolomics approach to study the phytochemicals of tomato cultivars grown under different salinity conditions

Authors: TAREQ, FAKIR - University Of Maryland; SINGH, JASHBIR - Orise Fellow; Ferreira, Jorge; Sandhu, Devinder; Suarez, Donald; Luthria, Devanand - Dave

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2024
Publication Date: 3/26/2024
Citation: Tareq, F.S., Singh, J., Ferreira, J.F., Sandhu, D., Suarez, D.L., Luthria, D.L. 2024. A targeted and an untargeted metabolomics approach to study the phytochemicals of tomato cultivars grown under different salinity conditions. Journal of Agricultural and Food Chemistry. 72(14):7694-7706. https://doi.org/10.1021/acs.jafc.3c08498.
DOI: https://doi.org/10.1021/acs.jafc.3c08498

Interpretive Summary: Freshwater scarcity is becoming the most critical environmental factor across the globe for irrigated agriculture, mainly in arid and semi-arid climates. This escalating demand to maintain food security for an expanding population compels us to consider alternative, degraded, water sources for irrigation. After drought, salinity emerges as a leading abiotic stress that limits plant growth and productivity. In this study, we aim to evaluate the effect of increasing the concentration of sulfate and chloride salts in irrigation water, on the metabolic content and profiles of tomato cultivars (Jaune Flamme and Red Pear). We aim to use targeted and untargeted approaches applying chromatographic and spectroscopic techniques followed by multivariate analysis. The present findings suggest that different salinity conditions significantly influenced the accumulation of phytochemicals in tomato cultivars. This study will help tomato breeding programs select tomato cultivars with high functional qualities for saline environmental conditions.

Technical Abstract: In this study, we evaluated the effect of increasing salinity of irrigation water on the metabolic content and profiles of tomato cultivars (Jaune Flamme and Red Pear) using targeted and untargeted metabolomics approaches. Irrigation of tomato plants was performed with different salt concentrations (control, 3.0, 4.5, and 6.0 dS m-1), provided by chloride (treatment 1) and sulfate (treatment 2) salts. The metabolic features of methanol extracts of ground tomato samples were obtained using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) in both positive and negative ionization modes. Targeted methanolic extract analysis resulted in the identification of nine major polyphenols. Among them, chlorogenic acid, rutin, and naringenin-II were the prominent compounds in both cultivars. Similarly, 18 free amino acids were quantified from both tomato cultivars, and results showed that different salinity treatments significantly enhanced the levels of glutamine, glutamic acid, and GABA. No significant variations were observed between the two cultivars grown in different salinity conditions in terms of total polyphenols or total amino acid content. In contrast, a total of 129 metabolites were identified putatively using the untargeted approach belonging to several classes of phytochemicals, including polyphenols, organic acids, lipids, sugars, and amino acids. However, principal component analysis (PCA) of features collected in both positive and negative ionization modes of 129 compounds showed a clear separation between two tomato cultivars. Unsupervised and supervised learning algorithms were applied to mine the generated data and to pinpoint metabolites differentiating the two cultivars. In addition, PCA analysis of features that were acquired under positive ionization showed a clear separation among independent treatment samples from both cultivars, but no separation was observed from the data acquired in negative ionization. These findings suggest that different salinity conditions significantly influenced the accumulation of phytochemicals in tomato cultivars. This study will help tomato breeding programs select tomato cultivars with high functional qualities for saline environmental conditions.