Morpho-Physiological, Biochemical, and Genetic Responses to Salinity in Medicago truncatula

Abstract

We used an integrated morpho-physiological, biochemical, and genetic approach to investigate the salt responses of four lines (TN1.11, TN6.18, JA17, and A10) of Medicago truncatula. Results showed that TN1.11 exhibited a high tolerance to salinity, compared with the other lines, recording a salinity induced an increase in soluble sugars and soluble proteins, a slight decrease in malondialdehyde (MDA) accumulation, and less reduction in plant biomass. TN6.18 was the most susceptible to salinity as it showed less plant weight, had elevated levels of MDA, and lower levels of soluble sugars and soluble proteins under salt stress. As transcription factors of the APETALA2/ethylene responsive factor (AP2/ERF) family play important roles in plant growth, development, and responses to biotic and abiotic stresses, we performed a functional characterization of MtERF1 gene. Real-time PCR analysis revealed that MtERF1 is mainly expressed in roots and is inducible by NaCl and low temperature. Additionally, under salt stress, a greater increase in the expression of MtERF1 was found in TN1.11 plants than that in TN6.18. Therefore, the MtERF1 pattern of expression may provide a useful marker for discriminating among lines of M. truncatula and can be used as a tool in breeding programs aiming at obtaining Medicago lines with improved salt tolerance.

Evaluation of the Morpho-Physiological, Biochemical and Molecular Responses of Contrasting Medicago truncatula Lines under Water Deficit Stress

“…In the current study, most of the correlations between traits were positive, suggesting that most of the measured characters were similarly affected by water deficit stress. The dry and fresh plant weights were positively correlated with the numbers of leaves, suggesting that the reduction in biomass is related to the number of leaves for A10, as reported by Yu et al [45] and by Hdira et al [32], for Rosaceae species and M. truncatula, respectively. Among these correlations, the number of axes was negatively correlated with all the traits.…”

“…Our results showed that the variation of measured traits was mainly influenced by the water deficit stress, which has caused a significant reduction in the leaf number, plant height, number of axes, and length of roots in all lines, with the highest reductions noted for the TN10 line. Accordingly, Hdira et al [32] reported significant reductions for growth parameters in the same lines under salt stress conditions. The fresh and dry biomasses are generally considered as indicators to select tolerant lines at the seedling stage [33,34].…”

“…In order to control the water content in the pots, weighing was carried out for each pot every two days, after which the plants were watered to maintain levels of 100% and 30% FC. Furthermore, osmotic stress (induced by 100 mM NaCl) was applied to plants as described by Hdira et al [32].…”

“…Malondialdehyde (MDA), soluble sugars, and protein contents were determined, in the leaves and roots of the tested lines under the three treatments, as described by Hdira et al [32]. Three replicates per line and per treatment were used.…”

“…The total RNA extraction was from different tissues of the studied lines, as described by Zeng and Yang [74]. The evaluation of the total extracted RNA and cDNA synthesis was performed as described by Hdira et al [32]. The quantification of the level of DREB1B transcripts in the different tissues of plants under control treatment and stress conditions was carried out using quantitative real time and was detected with SYBR Green (Roche, Mannheim, Germany) as described by Hdira et al [32].…”