Haythem Mhadhbi

This study investigated the impact of seed coat removal (decortication) on the phenolic composition and antioxidant activities of two Tunisian faba bean (Vicia faba L.) cultivars (Local Nabeul and Local Beja). The total phenolic, flavonoid, and tannin contents, alongside three antioxidant activity assays (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, β-carotene bleaching inhibition, and total antioxidant ability), were measured in whole and decorticated seeds. The results indicated that decortication did not significantly alter total phenolic and flavonoid content but variably influenced specific antioxidant activities depending on the cultivar. Notably, DPPH radical scavenging activity improved by 25–35% following decortication, suggesting that removal of the seed coat eliminated interfering compounds such as tannins, thereby enhancing the extract's free radical neutralizing efficiency. Conversely, total antioxidant ability slightly decreased, indicating the loss of some pro-oxidant or metal-reducing compounds concentrated in the hull. Tannin content was identified as the primary discriminating variable between cultivars and was significantly reduced by the process. Multivariate analyses, including Principal Component Analysis (PCA) and hierarchical clustering, demonstrated distinct discrimination among samples. Local Beja Whole Seeds (LBWS) clustered distinctly due to its high tannin content, while decorticated samples from both cultivars grouped together. This reveals that processing can dominate cultivar-based differences in functional properties. This study demonstrates that decortication's effect is not uniform but rather dependent on both the specific cultivar and the antioxidant mechanism evaluated, providing crucial insights for optimising faba bean processing to balance nutritional retention with sensory improvement.

Salt stress is a major abiotic factor limiting crop productivity worldwide, as it disrupts plant growth, metabolism, and survival. In this study, we report that the genes PvPR10-2 and PvPR10-3 were significantly up-regulated in bean leaves and stems in response to combined salt and jasmonic acid (NaCl–JA) treatment. Foliar application of JA with salt induced physiological alterations, including stem growth inhibition, H₂O₂ accumulation, and activation of antioxidant enzymes. To investigate the role of PvPR10-3 in response to salt and phytohormones, we introduced this gene into Arabidopsis and found that its heterologous expression conferred salt tolerance to the transgenic lines. Interestingly, exogenous JA contributed to salt tolerance by reducing H₂O₂ levels, inducing ROS-scavenging enzymes, and promoting the accumulation of phenolic compounds and ABA. Furthermore, gene expression analysis of the transgenic lines revealed that PvPR10-3 expression under NaCl–JA stress is associated with the induction of JA-related genes like MYC2, JAZ2, JAZ11, and JAZ12, as well as SA-responsive genes, like ALD1 and TGA2, and two ABA-independent components DREB2A and ERD1, suggesting potential coordination between JA, ABA, and SA signaling in salt stress response. Additionally, key flowering regulators (FT, GI) were upregulated in transgenic lines under NaCl–JA treatment, suggesting a previously unexplored link between salt tolerance pathways and the regulation of flowering time. Taken together, our findings suggest a role of PvPR10-3 in enhancing salt stress tolerance and the involvement of exogenous JA in tolerance potentially by modulating ROS balance, hormone-associated gene expression, and protective secondary metabolites.

Context: Pesticides are widely used to control crop diseases and pest infestations. However, their excessive and unregulated use poses considerable environmental challenges. Aims: To evaluate the effects of dimethoate on the germination and seedling growth of Vicia faba, V. sativa, Trigonella foenum-greacum, and Medicago truncatula. Methods: Physiological and biochemical changes were studied under different dimethoate concentrations (0, 0.4, 0.8 and 1.2 g L−1). Key results: Results showed that dimethoate significantly inhibited growth in all species, especially at 1.2 g L−1 of dimethoate. This negative effect was accompanied by reactive oxygen species (ROS) accumulation and lipid peroxidation (malondialdehyde, MDA) induction. Different behaviors were shown among the studied species. M. truncatula was the most sensitive, exhibiting toxicity even at the lowest concentration. In contrast, T. foenum-graecum showed remarkable tolerance, maintaining better growth at the highest dose compared to the two others species. The results of statistical analyses, including Pearson’s correlation and principal component analysis, support the use of fenugreek as a tolerant cover crop. Conclusion: T. foenum-graecum’s tolerance was associated with a lower reduction in total soluble sugars (25%) and a significant increase in antioxidant enzyme activity, particularly superoxide dismutase (70%). These adaptations are likely to help T. foenum-graecum cope with oxidative stress and maintain growth despite pesticide exposure. Implications: The results offer valuable decision support for using T. foenum-graecum as a cover crop in the field when using dimethoate in pest control at grapevine and citrus fields.

Broomrapes (Orobanche spp.) are root parasitic plants that threaten agricultural production in many parts of the world. In this study, the effect of two orobanche species, Orobanche crenata and O. foetida, on faba bean plants was studied in Tunisia. The two orobanche species inhibited both biomass production and pod formation, decreased the chlorophyll (Chl) content and total lipid (TL), and enhanced electrolyte leakage (EL) and lipid peroxidation. Concomitantly, orobanche parasitism induced a lower degree of fatty acid (FA) unsaturation due to a shift in the FA composition. On the other hand, with regard to orobanche seeds, oleic and linoleic acids were the predominant FA in the two orobanche species. After orobanche seed germination and penetration of host tissues, all the orobanche development stages showed a decrease in the TL content and changes in the FA composition in comparison to orobanche seeds. The level of TL was equal to or lower in all parasite development stages (except for S4) than that in the roots and leaves of healthy faba bean plants. These results suggest that the negative effect of orobanche infestation on faba bean development can be attributed to the reduced chlorophyll content and alteration in membrane stability attested by the reduced TL level and FA unsaturation.

Drought is an environmental stress that strongly impacts plants. It affects all stages of growth and induces profound disturbances that influence all cellular functions. Legumes can establish a symbiosis with Rhizobium-type bacteria, whose function is to fix atmospheric nitrogen in organs called nodules and to meet plant nitrogen needs. Symbiotic nitrogen fixation (SNF) is particularly sensitive to drought. We raised the hypothesis that, in drought-stressed nodules, SNF inhibition is partly correlated to hypoxia resulting from nodule structure compaction and an increased O₂ diffusion barrier, and that the nodule energy regeneration involves phytoglobin–nitric oxide (Pgb–NO) respiration. To test this hypothesis, we subjected faba bean (Vicia faba L.) plants nodulated with a Rhizobium laguerreae strain to either drought or osmotic stress. We monitored the N₂-fixation activity, the energy state (ATP/ADP ratio), the expression of hypoxia marker genes (alcohol dehydrogenase and alanine aminotransferase), and the functioning of the Pgb–NO respiration in the nodules. The collected data confirmed our hypothesis and showed that (1) drought-stressed nodules were subject to more intense hypoxia than control nodules and (2) NO production increased and contributed via Pgb–NO respiration to the maintenance of the energy state of drought-stressed nodules.

The present study was carried out in order to investigate the behaviour of six faba bean (Vicia faba Minor) genotypes (Saber 02, Locale, Baachar, Badii, Chourouk and Najeh) in response to salinity and flooding (hypoxia), either alone or combined, to identify tolerant genotypes and to select efficient faba bean-rhizobia symbiosis under salinity and/or hypoxia conditions. faba bean genotypes were cultivated in three agricultural soils with either low (160 µs/cm) or moderate (1850 µs/cm) salt content and submitted or not to a 30-day long flooding period. Growth parameters and photosynthetic performance were analyzed at the end of the flowering period. At harvest time, the Najeh genotype showed the highest dry mass production in both control and hypoxia conditions (7.90 and 6.75 g/plant, respectively), whereas Saber 02 showed the lowest (3.75 and 2.25 g/plant, respectively). Differences between genotypes were less marked in salinity or combined salinity/flooding conditions. Principal component analysis of the analyzed parameters revealed that the Najeh genotype presents the best growth and the lowest photosynthetic perturbation and lipid peroxidation levels, whether under control or hypoxic conditions, whereas Saber 02 and Locale genotypes were less productive. Ninety bacteria strains were isolated from Vicia faba root nodules. Of these, 47 strains were identified as rhizobia, and 20 were able to re-nodulate the host plant. After the characterization, identification and selection process, four strains were selected as the best faba bean symbiotic partners based on their symbiotic efficiency and salt tolerance behaviours. Our results suggest that faba bean tolerant genotypes in symbiosis with these strains could be useful in enhancing legume cultivation under saline and hypoxia field conditions.

Context: Heavy metal contamination of soils is a serious environmental problem worldwide. Cadmium (Cd) and lead (Pb) are considered among the most important types of pollutants. Aim: To investigate the response of a local fenugreek cultivar against lead and cadmium. Methods: Physiological changes were studied under different concentrations (0, 100, 200, 300 and 400 μM) of PbCl2 and CdCl2. Key results: Fenugreek growth decreased gradually with increasing Cd and Pb supply. This decrease was accompanied by a gradual decline in shoot and root length and photosynthetic parameters. However, Cd treatments showed pronounced effects in fenugreek seedlings as compared to Pb. The tolerance index was between 0.41 and 0.81, which suggests relative tolerance of this cultivar to Pb and Cd. This species was also able to maintain stable water status. Nevertheless, in presence of high Cd concentration (400 μM), this species showed substantial decrease in CO2 assimilation (86%), transpiration rate (87%), stomatal conductance (57%), chlorophyll content (35%) and carotenoid content (53%). Shoot proline content was increased significantly under 200 and 300 μM Cd, and slightly under 100 and 200 μM Pb. Furthermore, Cd and Pb induced a decrease in shoot magnesium and phosphorus content. Conversely, shoot iron content was increased. Data showed that fenugreek accumulated Cd, and translocated to the harvestable parts (up to 20 mg/kg DW under 400 μM). However, Pb was mostly accumulated in roots. Conclusions: Our results revealed that the relative tolerance of fenugreek to Pb excess was coupled to a remarkable accumulation of this element in root, which favourite the phytostabilisation process. Implications: FM, FL, SJ and OTZ execute the manipulation and the culture of plants. FM, OTZ, IN and KZ analyse and examine obtained results. FM, OTZ and KZ write and preparethe manuscript. IN, HM and KZ prepare the conception and the realisation ofthis work.

Fusarium and Rhizoctonia genera are important pathogens of many field crops worldwide. They are constantly evolving and expanding their host range. Selecting resistant cultivars is an effective strategy to break their infection cycles. To this end, we screened a collection of Medicago truncatula accessions against Fusarium oxysporum, Fusarium solani, and Rhizoctonia solani strains isolated from different plant species. Despite the small collection, a biodiversity in the disease response of M. truncatula accessions ranging from resistant phenotypes to highly susceptible ones was observed. A17 showed relative resistance to all fungal strains with the lowest disease incidence and ratings while TN1.11 was among the susceptible accessions. As an initiation of the characterization of resistance mechanisms, the antioxidant enzymes’ activities, at the early stages of infections, were compared between these contrasting accessions. Our results showed an increment of the antioxidant activities within A17 plants in leaves and roots. We also analyzed the responses of a population of recombinant inbred lines derived from the crossing of A17 and TN1.11 to the infection with the same fungal strains. The broad-sense heritability of measured traits ranged from 0.87 to 0.95, from 0.72 to 0.96, and from 0.14 to 0.85 under control, F. oxysporum, and R. solani conditions, respectively. This high estimated heritability underlines the importance of further molecular analysis of the observed resistance to identify selection markers that could be incorporated into a breeding program and thus improving soil-borne pathogens resistance in crops.