Analysis of salinity-induced metabolome changes in Indian mustard (Brassica juncea) roots and shoots: hydroponic versus microplot cultivation.

Abstract

Brassica juncea L. (family Brassicaceae) or Indian mustard is a fast-growing oilseed crop. Climate changes mean that it is very important to evaluate the effects of salinity stress on B. juncea. The aim of this study was therefore to show the metabolic effect of salinity stress on shoots and roots using two cultivation models - hydroponic and microplot - in different cultivars, including RH-725 and RH-761. Salinity levels of 5, 7.5, and 10 dS m⁻¹ were investigated, and compared with a control of 0 dS m⁻¹, using untargeted metabolomics with gas chromatography-mass spectrometry (GC-MS) post-silylation, focusing on metabolic markers such as proline and glycine-betaine. A total of 56 metabolites were identified, with the most prevalent classes belonging to sugars (8), followed by organic acids (13), amino acids (11), and fatty acids/esters (11). Shoots were found to have a higher sugar content than roots. Increases in unsaturated fatty acids were also associated with salinity stress, compared with a decrease in saturated fatty acids. Absolute levels of proline and glycine-betaine correlated with salinity stress, with the largest increases detected in shoots grown under hydroponic conditions, particularly for the RH-761 cultivar. Multivariate data analyses revealed that roots were more affected than shoots, regardless of cultivation model. These findings might explain the different metabolic behavior of B. juncea's roots and shoots under various levels of salinity, associated with higher levels of free sugars in shoots and lipids in roots. © 2024 Society of Chemical Industry.