Search

To understand the salinity tolerance mechanism in faba bean contrasting pair to salinity (cv. Chourouk as sensitive and cv. Najeh as tolerant), we evaluated the effect of high salt concentration (150 mM NaCl) on the photosynthetic, physiological, and biochemical parameters at short and long term of treatment (1 and 6 days, respectively) in the seedling stage. In general, the salinity affects the growth of plants. High salinity decreased all studied parameters, especially transpiration rate (E), stomatol conductance (gs), net CO2 assimilation (A), and substomatal CO2 concentration (Ci), and dramatic changes was registered in cv. Chourouk compared to cv. Najeh. Chlorophyll contents were also affected by salinity, especially in the sensitive variety. In addition, the synthesis of osmolytes (proline) was determinate, to understand whether the osmotic adjustment is a mechanism used by cv. Najeh to tolerate salt stress. Our research suggests that cv. Najeh should be introduced in a crossbreeding program as an elite salt-tolerant germplasm.

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.

Plants encounter a myriad of microorganisms at the root-soil interface that can invade with detrimental or beneficial outcomes. Promoting a symbiotic relationship may interfere with the restriction responses to pathogens. In this study, we established a tripartite Medicago truncatula- Sinorhizobium meliloti-Fusarium oxysporum interaction to study the effect of the interplay between symbiosis and defense on the symbiosis establishment and efficiency in a resistant (A17) and susceptible (TN1.11) genotype to F. oxysporum infection. Our results showed that Sm induced the expression of allene oxide cyclase 1 and 2 (MtAoc1) and (MtAoc2) at 6 and 24 hours post infection (hpi) in A17 and at 24 hpi in TN1.11. This up-regulation of MtAoc1 and MtAoc2 was also observed when co-inoculating TN1.11 genotype with Fo and Sm. Moreover, in this later treatment the expression level of the gene of the common signaling pathway doesn’t make infection 3 (DIM3) was reduced compared to Sm-inoculated plants. This reduction of DIM3 transcripts was concomitant to a decrease in nodule number (NN), nodule fresh weight, and nitrogen-fixing rate (NFR), and to an accumulation of spermine in nodules. This defectiveness in symbiosis parameters, in the co-inoculation treatment, was also observed in A17 genotype, along with an accumulation of phytohormones in leaves and polyamines in nodules. Our results suggest that in the tripartite interaction, the high expression of MtAoc and the decrease of DMI3 transcripts along with the accumulation of phytohormones and polyamines in leaves overlapped with symbiosis establishment and functioning and thus, reduced NN and NFR.

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.

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 O

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.

Iron (Fe) deficiency leads to an overproduction of reactive oxygen species (ROS) in plants that activate their antioxidant systems to control oxidative burst. In this study, contrasting Medicago truncatula genotypes, A17 and TN8.20 (tolerant) and TN1.11 (sensitive), were grown under Fe deficiency. The superoxide dismutase (SOD: EC1.15.1.1) activity, their isoforms’ coding genes, the copper chaperone expression patterns, and leaf phenolic contents were analysed. Our results showed that Fe deficiency decreases the photosynthetic capacity and plant biomass production with a prominent effect on TN1.11 genotype. The tolerance of A17 and TN8.20 was correlated with a maintenance of Fe content and the photosynthetic apparatus and an increase of Cu concentration compared with the sensitive genotype. We revealed a significant increase of H2O2 in Fe-deficient plants, mainly in TN1.11 sensitive genotype. TN8.20 and A17 tolerance were concomitant with a significant increase of SOD activities (SOD, Cu/Zn-SOD, and Mn-SOD) under Fe deficiency. This increment was correlated to an induction of the copper chaperone gene expression level, as well as an accumulation of isoquercitin phenolic compound. Our study provides new insights into the orchestration of SOD’s isoforms activities, the expression of the copper chaperone, FeSOD, Cu/ZnSOD genes, and the leaf phenolic compounds accumulation that allows Medicago truncatula to overcome Fe deficiency.

Calcareous soils, characterized by a higher pH, are frequent in the North West of Tunisia. Large concentrations of calcium carbonate in calcareous soils result in accumulation of high levels of bicarbonate ions, which complex with phosphate, resulting in phosphorus deficiency (induced P deficiency) for plants. The impact of calcareous soil on plant growth, photosynthetic activity and acid phosphatase activity was explored in two lines of Medicago truncatula: TN6.18 and Jemalong. Calcareous soil significantly restricted shoot growth only in Jemalong (-45 % of the control). When grown on calcareous soil, root length was stimulated, this effect being more pronounced in TN6.18. Under calcareous soil, net CO2 assimilation declined more in Jemalong (-40 % of the control) than in TN6.18 (-20 % of the control). CO2 accumulation was increased in Jemalong (+35% of the control) plants grown in calcareous soil. The acid phosphatase activity was higher in plants cultivated under calcareous soil. This increased phosphatase activity was more pronounced in TN6.18, which showed higher accumulation of Pi in shoots and roots than Jemalolng. In the light of these results, the present study proposes acid phosphatase as a useful candidate for improving Pi acquisition and utilization under calcareous soil.

The characterization of PR10 proteins has been conducted in many plant species. However, little is known about the roles of PvPR10 in response of common bean (Phaseolus vulgaris L.) to stress. Thus, for the first time a genome wide analysis revealed that the 34 genes of Bet v 1 family were divided into three major subfamilies according to phylogenetic relationship analysis from P. vulgaris and other plant species. The analysis uncovered that tandem duplication was the major force in the expansion of the Bet v 1 family genes in P. vulgaris and two other Fabaceae plants. Furthermore, the gene structure and motifs examination revealed that genes of Bet v 1 family were relatively conserved during evolution. Likewise, we recognized in the PvPR10 promoter regions several cis-regulatory elements related not only to abiotic and biotic stresses but also to phytohormones. In P. vulgaris, several PvPR10 genes exhibited differential expression profiles in many developmental tissues and organs. Notably, the expression profiles showed that essentially the two genes PvPR10-2 and PvPR10-3 genes were up-regulated under various treatments. Besides, the combined NaCl-JA stress enhanced their expressions in leaves and stems. Finally, we noticed that these inductions seem to be correlated with the enhancement of the expression of ABA biosynthesis PvNCED3 gene and the transcription factor PvDREB. Taken together, these data provide a foundation for further functional studies of certain PvPR10 that could be used in various stress tolerance improvements.

The aim of this study was to evaluate the effect of the addition of biochar (0, 2, 5, and 8% designed by C, B2, B5, and B8, respectively) on the single and interactive effects of salinity and drought treatments on the growth of vicia faba plants in alkaline soil. 21 morphological, physiological, and photosynthetic parameters were evaluated. The amendment of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, in alkaline soil under salinity stress performed positive effects on internal concentration of CO2 (+ 96.16% at B8), transpiration rate (+ 83.79% at B5), stomatal conductance (+ 30% at B2), and net CO2 assimilation (+ 37.84% at B2). Under drought stress, the addition of biochar had no effect on internal concentration of CO2 and the water use efficiency. Under combined conditions, the maximum increase (+ 40%) of internal concentration of CO2 was registered at B5. Also, addition of 2% of biochar (B2) can increase the transpiration rate to + 116%. Biochar was alleviating the effect of combined stress on vicia faba leaves by ameliorating the stomatal conductance to + 58.73% at B2. We, also, noticed that net CO2 assimilation rate increase with the increase of biochar concentration. On the other hand, biochar addition did not have effect on lengths of shoot, roots, and total plants and fresh biomass, spad value, and leaf number. However, the amendment of biochar has slightly ameliorated the electrolyte leakage, protein content, and foliar surface. The pH and the EC of initial and final treatment were also evaluated. The statistical analysis demonstrates that addition of 2% (B2) of biochar can significantly mitigate the negative effect of single effect of salinity and combined salinity drought in alkaline soil. On the other hand, the addition of 5% (B5) of biochar can alleviate the individual effect of drought compared to their respective controls. This result confirms the positive effect of biochar addition in alkaline soils. Thus, a better understanding of biochar addition on physiological basis for faba bean growth under drought and salinity stress in alkaline soil will be beneficial for sustainable agriculture.

This study evaluated the antifungal activity of NPs against Botrytis cinerea, the causal agent of grey mould, which is an important fungal diseases in several crops. In addition, a green method for...

The present work was initiated in order to test whether the growth and pathogenic behavior of fungal isolates infecting Faba bean (FB) are influenced by salt and drought stress. A collection of 108 fungal isolates was recovered from different infected FB plants grown in various bioclimatic zones in Tunisia. Koch’s postulates revealed that 54% of those isolates caused root rots infection by 25% to 100% of the whole root system. Eighteen pathogenic fungal isolates were chosen based on their high incidence on various plant growth parameters using the heat map analysis to undergo the in vitro analysis, where 13 isolates belong to Fusarium spp. The in vitro mycelial growth of the 18 strains in potato-dextrose agar amended with NaCl and PEG6000 was strain dependent, in which F. equiseti (VFF12, VFF16), F. graminearum VFF6, F. brachygibbosum VFF9, Alternaria sp. VFF5, Boeremia exigua VFF4, Rutstroemia sp. VFF7 and Rhizopus oryzae VFF1 showed a significant increase by up to 150% compared to controls. Best linear unbiased predictors (BLUPs) for differences in root and shoot dry weights between control (inoculated unstressed plants) and inoculated under salt and drought stress of the tolerant fungal strains were analyzed. BLUPs of VFF16, VFF6, and VFF7 were significantly increased under both stresses compared to controls. While, BLUBs of VFF12, VFF9, and VFF4 were not significant, which maintained similar pathogenic effect. However, BLUPs of VFF5 and VFF1 were significantly decreased. Consequently, soil salinization and water deficiency - occurring nowadays in many parts of the world - can increase the aggressiveness of phytopathogenic fungi.

Phytopathogen infection alters primary metabolism status and plant development. The alternative oxidase (AOX) has been hypothesized to increase under pathogen attack preventing reductions, thus optimizing photosynthesis and growth. In this study, two genotypes of Medicago truncatula, one relatively resistant (Jemalong A17) and one susceptible (TN1.11), were infected with Fusarium oxysporum and Rhizoctonia solani. The in vivo foliar respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) were measured using the oxygen isotope fractionation. Gas exchange and photosynthesis-related parameters were measured and calculated together with antioxidant enzymes activities and organic acids contents. Our results show that the in vivo activity of AOX (valt ) plays a role under fungal infection. When infected with R. solani, the increase of valt in A17 was concomitant to an increase in net assimilation, in mesophyll conductance, to an improvement in the maximum velocity of Rubisco carboxylation and to unchanged malate content. However, under F. oxysporum infection, the induced valt was accompanied by an enhancement in the antioxidant enzymes, superoxide dismutase (SOD; EC1.15.1.1), catalase (CAT; EC1.11.1.6) and guaiacol peroxidase (GPX; EC1.11.1.7), activities and to an unchanged tricarboxylic acid cycle intermediates. These results provide new insight into the role of the in vivo activity of AOX in coordinating primary metabolism interactions that, partly, modulate the relative resistance of M. truncatula to diseases caused by soil-borne pathogenic fungi.

In this study, we examined the behavior of six faba bean (Vicia faba L.) genotypes under salinity conditions at the seedling stage. The evaluation was assessed using 21 morphological, physiological, and photosynthetic traits under control, moderate, and severe salinity conditions. The principal component analysis (PCA) was used to identify genotypes of contrasting behavior in response to salt stress and to characterize the important traits for salt tolerance. The result of PCA analysis showed that the genotypes displayed different behavior under the saline conditions. The most discriminating quantitative characters were related to plant biomass production and photosynthesis, especially the mass of fresh root, number of leaves, water-use efficiency, and the substomatal CO2 concentration. The analysis of all parameters by PCA permits us to distinguish cv. Najeh as the most tolerant genotype for salinity conditions and cv. Chourouk as the most sensitive one. These results would be of pertinent tools in faba bean breeding programs.

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.

Seed priming is one of the potential physiological approaches to enhance seed germination under salt stress. The present study examined the role of two seed priming molecules, salicylic acid (SA) and hydrogen peroxide (H2O2), to enhance the salt tolerance in lentil seeds at germination stage. Salt stress caused significant decrease in germination percentage and primary root elongation. This decrease was associated with significant increase in lipid peroxidation and total lipid (TL) contents in embryonic axis. The catalase (CAT), guaiacol peroxydase (GPOX) and superoxide dismutase (SOD) activities remained unchanged or decreased significantly under the influence of salt stress, in both embryonic axis and cotyledons. Starch mobilization was not affected by salt stress. The two priming treatments effectively alleviated the negative effects of salt stress. SA and H2O2 applications after dose optimization resulted in significant enhancement of germination percentage and primary root elongation. No significant changes in starch, soluble sugars contents and SOD activity were detected following SA and H2O2 treatments. Seed priming treatments triggered the activities of GPOX and CAT and caused the reduction of lipid peroxidation especially in embryonic axis. TL content and especially the fatty acid C18:3 increased after SA applications. The better performance under salt stress of primed lentil seeds was associated with lower lipid peroxidation, and activation of enzymatic antioxidative defense system. Obtained results confirm the potential for using SA and H2O2 to improve germination and plant growth under salt stress conditions.

Alleviation of cadmium-induced root genotoxicity and cytotoxicity by calcium chloride (CaCl2) in faba bean (Vicia faba L. var. minor) seedlings were studied. Faba bean seeds were treated with H2O or 2% CaCl2 for 6 h before germination. Seeds were then exposed to 0 and 50 µM CdCl2 concentrations for 7 days. Genotoxic damaging effects of Cd was examined through the determination of the mitotic index (MI), chromosomal aberrations (CA) and micronucleus (MN) in the meristem cells of faba bean roots. Similarly, effects of Cd stress on metal accumulation, total membrane lipid contents, total fatty acid composition (TFA), lipid peroxidation as indicated by malondialdehyde production, soluble protein and non-protein thiols (NP-SH) contents, hydrogen peroxide production and the activities of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) were evaluated after 7 days of Cd stress in the seedling roots. Cd stress resulted in the reduction of MI, in addition to MN formation and CA induction in the roots of non-primed seeds (treated with H2O). Moreover, Cd induced lipid peroxidation, H2O2 overproduction and loss of membrane lipid amount and soluble protein content, and changes in the TFA composition in roots of faba bean seedlings. SOD activity declined, but CAT and GPX activities increased. However, seed pre-treatment with CaCl2 attenuated the genotoxic and cytotoxic effects of Cd on Vicia faba roots. The results showed that CaCl2 induced reduction of Cd accumulation, improved cell membrane stability and increased the antioxidant defence systems, thus reducing and alleviating Cd genotoxicity and oxidative damage.

Faba bean (Vicia faba L.) seeds were treated with H2O [nonprimed (NP)] or 2% CaCl2 [primed (P)] before germination for 6 h. After seven days, seedlings were exposed to 0 or 50 µM CdCl2 concentrations for three weeks. Under Cd treatment, P plants showed an improvement of gas-exchange characteristics, chlorophyll (Chl) and carotenoids contents as compared to NP plants subjected to Cd stress. Additionally, the values of Chl fluorescence were relatively similar to those of control, implying that no photodamage occurred. Moreover, under 50 µM Cd, the P plants exhibited lesser accumulation of hydrogen peroxide and superoxide radicals in leaves as compared to NP plants. Likewise, results showed that CaCl2-seed pretreatment alleviated adverse effects of Cd on electrolyte leakage. In conclusion, CaCl2 improved photosynthesis attributes of faba bean plants subjected to Cd stress by mitigating the adverse effects of Cd toxicity through a reduced generation of reactive oxygen species.

Respiration is very sensitive to waterlogged conditions. Under these conditions, plant roots suffer from lack of available oxygen. In fact, waterlogging reduces the exchange of gases between the plant and the atmosphere. When plants cannot receive sufficient oxygen level for respiration, they form aerenchyma in their roots which function as reservoirs of oxygen in the submerged plant. Aerenchyma is formed in maize (Zea mays) roots in response to different types of stress such as waterlogging, mechanical impedance, drought and nutrient deficiencies. Ethylene plays a crucial role in aerenchyma formation. Under waterlogged conditions, it can be cumulated in the submerged tissue and induces genes implicated in aerenchyma formation. These genes are related to calcium signaling, cell wall degradation and reactive oxygen species (ROS). In this review, the authors focused on the recent findings on aerenchyma in maize roots and explained the mechanisms of its formation under waterlogged conditions. Key words: Aerenchyma, maize root cortex, waterlogging, ethylene, programmed cell death.

The effect of calcareous soil on growth, photosynthetic gas exchanges, symbiotic nitrogen fixation (SNF), iron nutrition, and antioxidative enzymes activities was investigated in two lines of Medicago truncatula: TN8.20 and Jemalong. The results showed that growth (especially in shoots) was significantly lower on calcareous soil in both lines, but Jemalong was more impacted than TN8.20. Plants cultivated on calcareous soil showed significantly lower values for photosynthesis activity (as net CO2 assimilation and stomatal conductance) and nodule performance (nodulation, nodule growth and SNF), but this trend was more pronounced in the sensitive line (Jemalong). The better performance of TN8.20 as compared to Jemalong could be ascribed due to its aptitude to preferentially allocate iron to nodules, thereby ensuring nodule growth and a higher SNF activity, besides showing higher iron use efficiency for SNF. In both lines, superoxide dismutase (SOD, EC.15.1.1), catalase (EC.1.11.1.6), and peroxidase (POX, EC 1.11.1.7) activities were increased significantly when they were grown on a calcareous soil. Yet, this tendency was more pronounced in the tolerant line, TN8.20. Overall, our results strongly suggest that on calcareous soils, the successful adaptation of TN8.20 would be related to its ability to induce an antioxidant response in order to preserve important metabolic paths such as photosynthetic activity and symbiotic nitrogen fixation.

Among abiotic stress, the toxicity of metals impacts negatively on plants’ growth and productivity. This toxicity promotes various perturbations in plants at different levels. To withstand stress, plants involve efficient mechanisms through the implication of various signaling pathways. These pathways enhance the expression of many target genes among them gene coding for metal transporters. Various metal transporters which are localized at the plasma membrane and/or at the tonoplast are crucial in metal stress response. Furthermore, metal detoxification is provided by metal-binding proteins like phytochelatins and metallothioneins. The understanding of the molecular basis of metal toxicities signaling pathways and tolerance mechanisms is crucial for genetic engineering to produce transgenic plants that enhance phytoremediation. This review presents an overview of the recent advances in our understanding of metal stress response. Firstly, we described the effect of metal stress on plants. Then, we highlight the mechanisms involved in metal detoxification and the importance of the regulation in the response to heavy metal stress. Finally, we mentioned the importance of genetic engineering for enhancing the phytoremediation technique. In the end, the response to heavy metal stress is complex and implicates various components. Thus, further studies are needed to better understand the mechanisms involved in response to this abiotic stress.

Our research aimed to reveal the capacity of intercropping with Medicago sativa-rhizobia in the amelioration of grapevine growth in agricultural and a Cd/Pb contaminated soils. A local variety of grapevine was cultivated in monocropping and in intercropping with Medicago sativa inoculated or not with its associated rhizobia. Intercropping with alfalfa induced a significant increase in shoot and root biomass of grapevine in the agricultural soil. However, in the contaminated soil, a slight increase in root biomass was observed. Concerning photosynthesis apparatus, we showed that the presence of Cd and Pb in the soil induced a significant decrease in both CO2 assimilation rate and stomatal conductance. Interestingly, intercropping with alfalfa only and with rhizobia alleviate this effect. Similar results are obtained for chlorophyll and carotenoid content. This was associated with a significant decrease in the malondialdehyde level in leaves and roots of grapevine cultivated in intercropping with alfalfa with and without inoculation in the two soils as compared the monoculture treatment. Comparison between treatments revealed also that intercropping with alfalfa induced a decrease in the activities of some enzymes implicated in the defence to the oxidative stress such as catalase and superoxide dismutase. Regarding soluble protein content, it is needed to signal the improvement of this parameter with the intercropping system in the contaminated soil when compared to the monocropping treatment. This work highlights the importance of the use of legumes in intercropping with grapevine as intercrop plant non-competitive for soil nutrient and proving N supply for associated plants.

Faba bean (Vicia faba L.) is an important pulse crop in the Mediterranean region. Salinity is one of the most devastating abiotic stresses that alter the growth and development of plants and affect the crop yield, especially in arid and semi-arid area such as Tunisia. To surmount the damaging effect of salinity, it is important to develop tolerant cultivars of faba bean. In this study, we examined the behavior of four faba bean cultivars in response to salinity stress. Plants were grown in hydroponics at 0, 75 and 150 mM of NaCl, and 16 morphological, photosynthetic and physiological parameters were assessed. Our data showed a significant genotypic variation for salt tolerance in faba bean among the studied cultivars. All measured parameters were affected by salinity at moderate salt concentration (75 mM), while there was a more pronounced reduction of all parameters at severe salt concentration (150 mM). The statistics analysis revealed that photosynthetic and biomass parameters were the least altered in cv. ‘Najeh’. Based on the results, cv. ‘Najeh’ can be considered to be a tolerant cultivar and to attract great interest in future breeding programs for modern cultivar improvement.

Low-temperature plasma is usually a kind of high-energy aggregated state produced by gas ionization through gas discharge...

The first experiment was conducted to evaluate the impact of seed priming on germination behavior and seedling establishment in Vicia faba and Vicia sativa, for that, seeds priming was done using SA (100 µM) and KH2PO4. In order to determine the optimal concentration of KH2PO4 for improving germination, different concentrations were used: 25 µM, 50 µM, and 100 µM. The best germination behavior and seedling establishment were obtained with 25 and 50 µM KH2PO4, respectively for Vicia faba and Vicia sativa. Moreover, data showed that 100 µM of SA improved seed germination as well as the seedling establishment for both species. The second experiment was carried out to investigate the influence of seed priming for improving phosphorous (P) deficiency tolerance. To do, seedling obtained from primed and nonprimed seeds were grown in a hydroponic culture system with three different treatments: control (C, medium containing sufficient P concentration: 360 µM KH2PO4), direct phosphorus-deficient (DD, medium containing only 10 µM KH2PO4), and induced P deficiency by bicarbonate (ID, medium containing sufficient P concentration: 360 µM KH2PO4 + 0.5 g L-1 CaCO3 + 10 mM NaHCO3). Furthermore, the role of exogenous SA applied to P deficiency tolerance enhancement was explored. Seed priming or the exogenous application of SA significantly reduced the severity effect of P deficiency. In fact, the pretreated plants were observed more tolerant to P deficiency as reflected from the significant increase in plant biomass, P uptake, and an efficient antioxidant system. Overall, this paper highlights the beneficial effect of seeds priming or the exogenous application of SA in the improvement of plant tolerance to phosphorus deficiency. A deficiência de fósforo (P) é um fator ambiental adverso comum que limita a produção agrícola em todo o mundo. Este estudo é uma avaliação do efeito benéfico da técnica de priming de sementes para tolerância à deficiência de P em Vicia faba e Vicia sativa. Para avaliar o impacto do condicionamento das sementes no comportamento germinativo de Vicia faba e Vicia sativa, suas sementes foram imersas em diferentes concentrações de KH2PO4 (25 µM, 50 µM e 100 µM) e em 100 µM de ácido salicílico (SA) por 24 h. Os resultados obtidos definiram KH2PO4 50 µM (para Vicia sativa) e KH2PO4 25 µM (para Vicia faba) como as concentrações ótimas que garantem uma melhor germinação das sementes. Além disso, os dados mostraram que a SA melhora a germinação de sementes e o estabelecimento de mudas. Posteriormente, para investigar a contribuição dessa técnica no aumento da tolerância à deficiência de P, sementes preparadas e não preparadas foram cultivadas em solução hidropônica com três tratamentos diferentes: controle (C, meio contendo concentração suficiente de P: KH2PO4 360 µM), deficiente em fósforo direto (DD, meio contendo apenas 10 µM de KH2PO4) e deficiência induzida de P por bicarbonato (ID, meio contendo concentração suficiente de P: 360 µM de KH2PO4 + 0,5 g l-1 de CaCO3 + 10 mM de NaHCO3). Além disso, o papel da SA exógeno aplicada no aumento da tolerância à deficiência de P foi explorado. A preparação das sementes ou a aplicação exógena de SA reduziu significativamente o efeito da severidade da deficiência de P. De fato, as plantas pré-tratadas foram observadas mais tolerantes à deficiência de P, refletidas no aumento significativo da biomassa da planta, na absorção de P e em um eficiente sistema antioxidante. No geral, este artigo destaca o efeito benéfico da priming de sementes ou a aplicação exógena de SA na melhoria da tolerância das plantas à deficiência de fósforo.

Among the 17Sustainable Development Goals (SDG) of the United Nations Development Program (UNDP), the goal 2 is “Zero...

There are species abundance, diversity and distribution especially in the tropics and subtropics which are undergoing...

Following expulsion of Adam & Eve (attaining knowledge of good and bad or the cause and effect of reproduction) from the “Garden of Eden”...

According to the United Nations estimation, the human population will be reaching 9.7 billion by mid-century and 11.2 billion by century’s end...

Legumes (Fabacea) plants are mainly known for their symbiotic relationship with soil nitrogen-fixing bacteria (rhizobia). This symbiosis requires the formation of new root structures called nodules. Besides rhizobia, nodules host several microbial species that may serve to enhance plant growth and disease resistance. In this study, we demonstrate that several endophytic bacteria isolated from nodules harbour plant growth promotion and biocontrol traits. A collection of 120 bacterial strains isolated from Faba bean (Vicia faba) and chickpea (Cicer arietinum) nodules were screened for their ability to inhibit phytopathogenic Fusarium solani on “In vitro” antibiosis tests. Sixteen best effective isolates were selected, identified and sequences were deposited in Genbank. These strains were all isolated from Faba bean nodules. These have the characteristics to produce siderophores and auxin as well as expression of some genes coding the production of the antibiotic compounds as Pyrrolnitrin (PRN), Phenazine (PHZ)… Based on the former PGPR and biocontrol characteristics, three strains; Rahnella aquatilis B16C, Pseudomonas yamanorum B12 and Pseudomonas fluorescens B8P were analyzed for their “In vivo” biocontrol potential in suppressing F. solani root rot of three cultivars of Faba bean under greenhouse conditions. The three strains significantly reduced the pathogen symptom severity. R. aquatilis B16C showed the best protecting potentiality with the three Faba bean cultivars and it is consequently, suggested as biocontrol agent for field application. Then again, our study confirms previous suggestion of legume nodules as untapped suitable source of beneficial microorganisms that can be used to control pathogens in a sustainable way.

Plant health largely depends on root-associated microorganisms that inhibit pathogens. Enriching the rhizosphere microbiome with beneficial bacteria has a high potential of supporting future sustainable food production. However, the introduced microorganisms often show low activity with a low survival rate. We propose to solve this limitation by co-inoculating beneficial bacteria with protists. Free-living protists are one of the main regulators of bacterial activity in the rhizosphere and can increase the density and activity of pathogen-suppressive microbes. We therefore hypothesized that protist-bacteria interactions may serve to enhance plant protection against soil-borne pathogens. We tested whether co-inoculating beneficial bacteria with protists increases plant protection against Fusarium solani S55, a fungal pathogen causing root rot. We inoculated Vicia faba seedlings with the disease-suppressing bacteria Rahnella aquatilis B16C and Pseudomonas yamanorum B12, alone or in combination with three different bacterivorous soil protists, Rosculus terrestris S14D1, Bodomorpha sp. C10D3 and Cercomonas lenta C5D5. We grew plants in Fusarium-infested soil and recorded the effect of inoculation on disease severity and pathogen density. We demonstrated that introduced bacteria and protists synergistically impact plant health. When introduced alone, both bacteria and protists provided a partial protection against Fusarium rot. Protists further modulated the performance of the bacteria in an idiosyncratic way, with some combinations offering an almost complete Fusarium solani S55 suppression. These results suggest that protists could form the base of a new generation of biological control strategies of soil-borne diseases, either as a standalone inoculant or as an enhancer of beneficial bacteria.

Fusarium wilt caused by root infections by Fusarium equiseti is a serious disease of Vicia faba that causes significant economic losses in bean. Among management strategies, biological control is a sustainable alternative to chemical control, and Bacillus species emerge as suitable candidates. Bacillus strains have been developed in recent years as biocontrol agents of several plant diseases, mainly for fungal root disease control. In this study, 24 strains of Bacillus spp. were selected among 455 isolates obtained from V. faba plants for their antifungal activity against a broad-spectrum of phytopathogenic fungi belonging to Fusarium, Alternaria, Penicillium, Botrytis, and Rutstroemia genera. Particularly, the strains which inhibited growth of F. equiseti were identified as B. cereus, B. mojavensis, B. velezensis, B. subtilis and B. amyloliquefaciens by sequencing rpoB gene. The strains were further characterized for the presence of cyclolipopeptides (cLP) genes (fenD, bmyB, spaS, dfnM, ituA, mycA, srfAA), genes encoding plant-induced resistance factors (ysnE, yxvQ, β-Glu), and for the production of lipopeptides (iturins, fengycins, surfactins), indoleacetic acid, siderophores, hydrocyanic acid, extracellular enzymes (amylase, protease, pectinase, cellulase) and phosphate solubilization. Hierarchical and correspondence analysis showed the clustering of Bacillus strains into three different groups, where the strains with the highest antifungal activity are correlated to the presence of different biosynthetic genes and production of broad spectra of metabolites. They include strains of B. amyloliquefaciens, B. velezensis, B. subtilis and B. mojavensis. Furthermore, these strains showed high levels of Fusarium wilt reduction in V. faba under greenhouse conditions, as well as they have shown plant promoting activity. info:eu-repo/semantics/acceptedVersion

Bacterial and arbuscular mycorrhizal symbiosis are both beneficial for bacteria or fungus and host plants. The bacterial symbiosis enhances plant growth and productivity and it is beneficial for sustainable agriculture. In fact, rhizobia are soil bacteria that form symbiosis with legumes and help in fixing atmospheric nitrogen by converting into ammonia inside the root nodules. Legumes-rhizobia interaction is specificity controlled by various genetic and molecular mechanisms. Here we review the different components and molecules implicated in this interaction. Moreover, we detailed the genes coding for Nod factor secreted by bacteria and their receptors present on the cell membrane of plant host. The perception of Nod factors by their receptors leads to activate various signaling pathways that involve different transcription factors depending on the symbiotic stage. Nodule inception NIN proteins are crucial for nodulation organogenesis through the activation of target proteins. Finally, we reviewed the response of rhizobia and plants to environmental stress and their strategy to adapt stress.

This study was designed to highlight the impact of calcium chloride (CaCl2) seed priming on faba bean nodulation and root nodule oleosomes under cadmium stress. In the un-primed plants, high Cd exposure (50 μM) led to a decrease in nodule number and dry weight by 63% and 76% respectively as compared to control. Furthermore, metal supply resulted in a decrease (by 46%) in lipid content and the level of saturated fatty acids of oleosomes. However, CaCl2 seed priming improved nodule number by 23% and 20% and dry weight by 34% and 7% at 0 and 50 μM Cd respectively, compared to the control. Moreover, results showed that CaCl2 alleviated adverse effects of Cd on oleosome lipid content and fatty acid composition. Overall, CaCl2 seed priming was effective to alleviate the detrimental effects of Cd on some physiological and biochemical characteristics of faba bean root-nodule.

The volatile compounds of twelve legume cultivars were evaluated by headspace-solid phase micro-extraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC-MS) from both whole seeds and their flours. The total identification percentages of the extracted volatiles were ranged between 94.2% and 99.7%. The number of aroma compounds detected was 104. Among them, 60 compounds were determined in the emission of whole legume seeds and 69 from legume flours. The volatiles were classified into seven chemical classes, i.e. monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, phenylpropanoids, apocarotenes, nitrogen/sulfur derivatives, and non-terpene derivatives. Aldehydes were considered one of the most abundant constituents in non-terpene derivatives, followed by esters, alkanes, alcohols, ketones, lactones, phenols, phenones, alkenes, and hydrocarbons. A wide difference in term of volatiles was observed between whole and crushed seeds. Multivariate data analysis (PCA) was assessed to compare among legume cultivars, which leads to the identification of relevant constituents to specific cultivar. Overall, this is the first time a multivariate analysis was used to characterize the volatile profiles of twelve legume cultivars with their flours. This study can provide useful information on the conception of legume–based ingredients combined with specific volatile characteristics in order to reduce unwanted odors and definitely for pertinent breeding programs.

Unfortunately, many traditional crop germplasms are being abandoned by local farmers and newly introduced varieties are used instead, without any rigorous ecophysiological study regarding their adaptive potential to local environment. In Tunisian arid regions, where salt water is often used for irrigation, a commercial chard (Perpetual spinach) variety Sais has been introduced and is currently replacing an inherited one Arbi of Medenine. In the present work, we aimed to assess the differential response of these two chard varieties (Arbi, Medenine and Sais, Italy) to two salt treatments (7 and 14 g NaCl/l). In both Arbi and Sais shoots, salinity increase led to an endogenous accumulation of sodium and proline associated with a decrease in potassium levels. The lipid peroxidation products (Malondialdehyde, MDA) accumulation in Arbi was considerably greater than in Sais, indicating a higher degree of lipid peroxidation at 14 g/l salt treatment. Salinity stimulated the superoxide dismutase (SOD, E.C. 1.15.1.1), catalase (CAT, EC 1.11.1.6) and guaïacol peroxidase (GPX, EC 1.11.1.7) activities in Arbi shoot, even under severe salt stress (14 g/l). In contrast, these antioxidant enzymes were inhibited by NaCl in Sais shoots. It could be concluded that introduced chard (Sais) exhibited better growth and displayed similar metabolite levels relative to local one (Arbi), but the local chard seems to have stronger antioxidant system that may insure better adaption to water salinity.

In this study, the effect of the phyto-pathogenic fungus Fusarium oxysporum on Medicago truncatula-Sinorhizobium symbiosis performance was investigated. Fusarium oxysporum (KLR13) was inoculated on two genotypes of M. truncatula, one tolerant (Jemalong A17) and one susceptible (TN1.11), in symbiosis with Sinorhizobium meliloti (TII7), Sinorhizobium medicae (SII4) or fertilized with KNO3. Fungus infection reduced significantly biomass production and photosynthetic related parameters of non-symbiotic M. truncatula A17 and TN1.11. Reduction was less pronounced in A17, where a lower accumulation of H2O2 and lipid peroxidation (MDA) in concomitance to high activities of antioxidant enzymes, catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) was detected. In symbiosis, the fungus affected the nodule number and weight and inhibited the nitrogen fixing capacity (NFC), as well as the fructose and glucose contents. Nevertheless, inoculation with S. meliloti and S. medicae alleviated the effect of F. oxysporum on plant biomass production compared to the KNO3 fertilized plants. Moreover, the Sinorhizobium inoculation decreased H2O2 and MDA over-production caused by the fungal infection in leaves of both genotypes. This tolerance enhancing effect was more pronounced in S. medicae-TN1.11 symbiosis, where the relative maintenance of photosynthesis related parameters, growth capacity and NFC performance was concomitant to the induction of SOD and CAT activities and an increase of the sucrose content in leaves. For A17 genotype, both Sinorhizobium strains induced an increase of the proline and sucrose accumulation. In conclusion, F. oxysporum effect on M. truncatula was mitigated when plants were in symbiosis with Sinorhizobium species, mainly Sinorhizobium medicae that alleviated the oxidative stress and enhanced the accumulation of sucrose as energy source in TN1.11 genotype, which attenuates its susceptibility to F. oxysporum infection.

Alleviation of cadmium-induced root genotoxicity and cytotoxicity by calcium chloride (CaCl(2)) in faba bean (Vicia faba L. var. minor) seedlings were studied. Faba bean seeds were treated with H(2)O or 2% CaCl(2) for 6 h before germination. Seeds were then exposed to 0 and 50 µM CdCl(2) concentrations for 7 days. Genotoxic damaging effects of Cd was examined through the determination of the mitotic index (MI), chromosomal aberrations (CA) and micronucleus (MN) in the meristem cells of faba bean roots. Similarly, effects of Cd stress on metal accumulation, total membrane lipid contents, total fatty acid composition (TFA), lipid peroxidation as indicated by malondialdehyde production, soluble protein and non-protein thiols (NP-SH) contents, hydrogen peroxide production and the activities of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) were evaluated after 7 days of Cd stress in the seedling roots. Cd stress resulted in the reduction of MI, in addition to MN formation and CA induction in the roots of non-primed seeds (treated with H(2)O). Moreover, Cd induced lipid peroxidation, H(2)O(2) overproduction and loss of membrane lipid amount and soluble protein content, and changes in the TFA composition in roots of faba bean seedlings. SOD activity declined, but CAT and GPX activities increased. However, seed pre-treatment with CaCl(2) attenuated the genotoxic and cytotoxic effects of Cd on Vicia faba roots. The results showed that CaCl(2) induced reduction of Cd accumulation, improved cell membrane stability and increased the antioxidant defence systems, thus reducing and alleviating Cd genotoxicity and oxidative damage.

In this work, we have compared the physiological responses of alfalfa plants inoculated with either Sinorhizobium meliloti strain S412 (Cu-tolerant) or S112 (Cu-sensitive) in the presence or absence of 0.5 mM of CuSO4. The addition of copper (Cu) introduced a decrease of nodule number and their dry weight (DW) in both symbioses. The interaction established with the Cu-sensitive strain is more affected by Cu than that with the tolerant one. In fact, plants inoculated with the sensitive strain revealed a decrease of shoot and root DW, larger than that found in plants inoculated with the tolerant strain. However, under copper supply, Medicago sativa with the Cu-tolerant strain did not show any significant changes in both shoot and root biomass production. Under Cu excess, high levels of Cu were detected in different parts of the plant in the two symbioses and a high translocation of Cu to aerial parts was shown with the strain S412. Plants with S412 were able to accumulate large quantities of calcium (Ca) in...

The aim of this study was to assess the effect of symbiotic bacteria inoculation on the response ofMedicago truncatulagenotypes to iron deficiency. The present work was conducted on threeMedicago truncatulagenotypes: A17, TN8.20, and TN1.11. Three treatments were performed: control (C), direct Fe deficiency (DD), and induced Fe deficiency by bicarbonate (ID). Plants were nitrogen-fertilized (T) or inoculated with two bacterial strains:Sinorhizobium melilotiTII7 andSinorhizobium medicaeSII4. Biometric, physiological, and biochemical parameters were analyzed. Iron deficiency had a significant lowering effect on plant biomass and chlorophyll content in allMedicago truncatulagenotypes. TN1.11 showed the highest lipid peroxidation and leakage of electrolyte under iron deficiency conditions, which suggest that TN1.11 was more affected than A17 and TN8.20 by Fe starvation. Iron deficiency affected symbiotic performance indices of allMedicago truncatulagenotypes inoculated with bothSinorhizobiumstrains, mainly nodules number and biomass as well as nitrogen-fixing capacity. Nevertheless, inoculation withSinorhizobiumstrains mitigates the negative effect of Fe deficiency on plant growth and oxidative stress compared to nitrogen-fertilized plants. The highest auxin producing strain, TII7, preserves relatively high growth and root biomass and length when inoculated to TN8.20 and A17. On the other hand, both TII7 and SII4 strains improve the performance of sensitive genotype TN1.11 through reduction of the negative effect of iron deficiency on chlorophyll and plant Fe content. The bacterial inoculation improved Fe-deficient plant response to oxidative stress via the induction of the activities of antioxidant enzymes.

The aim of the present study was to evaluate abiotic stress tolerance of rhizobial strains belonging to Mesorhizobium, Sinorhizobium, and Rhizobium genera, as well as to investigate specie specific stress response mechanisms. Effect of NaCl and PEG on growth capacity, protein, lipid peroxydation (MDA), membrane fatty acid composition and antioxidant enzymes were investigated. Growth capacity and viability of overall rhizobia strains decreased proportionally to the increase of NaCl and PEG levels in the medium. Sinorhizobium strains appeared the most tolerant, where 4H41strain was able to grow at 800 mM NaCl and 40% PEG. On the other hand, growth of R. gallicum and M. mediterraneum was inhibited by 200 mM NaCl. The content of MDA was unchanged in Sinorhizobium strains under both stresses. For Mesorhizobium, only PEG treatment increased the content of MDA. Amount of the C19:0 cyclo fatty-acid was increased in both Sinorhizobium and Mesorhizobium tolerant strains. NaCl stress increased Superoxide dismutase (SOD) activity of overall species; especially the most tolerant strain 4H41. Both treatments increased catalase (CAT) activity in 4H41, TII7, and 835 strains. Obtained results suggest that major response of tolerant Sinorhizobium and Mesorhizobium strains to NaCl and PEG stresses is a preferential accumulation of the C19:0 cyclo fatty acid within bacterial membrane as mechanism to reduce fluidity and maintain integrity. Cell integrity and functioning is also assured by maintaining and/or increasing activity of SOD and CAT antioxidant enzymes for tolerant strains to omit structural and functional damages related to reactive oxygen species overproduced under stressful conditions. Abbreviations: CAT – catalase; CFA – cellular fatty acid; FAME – fatty acid methyl esters; MDA – malondialdehyde; ROS – reactive oxygen species; PEG – polyethylene glycol; PUFA – poly unsaturated fatty acid; SOD – superoxide dismutase; SDS PAGE – sodium dodecyl sulfate polyacrylamide gel electrophoresis

The ability of Phoma medicaginis to infect legume nodules and the subsequent effect on their functioning was investigated in Medicago truncatula lines, TN.8.20 and Jemalong6, inoculated with an efficient Sinorhizobium meliloti strain. Colonization of nodules by P. medicaginis strain Pm8 was confirmed by morphological and molecular analyses. P. medicaginis effect was more relevant on the most susceptible line, TN.8.20, where it decreased the nitrogen fixation capacity (NFC) significantly in nodules from 62 days after sowing (das) till the end of nodule life cycle; however in Jemalong6 nodules, the NFC inhibition was significant only at the flowering stage. Analyses of stress indices as structure, lipid peroxidation and leghemoglobin content did not show significant structural or metabolic alterations in infected nodules. Superoxide dismutase (SOD) activity was increased in nodules of both M. truncatula lines up to 62 das. After 78 das, increase of SOD activity continued only in Jemalong6 nodules. Changes in peroxidase (POX) activity were correlated to those revealed on NFC. Indeed, POX was decreased in nodules of TN.8.20 line but remained almost unchanged in Jemalong6. These results, suggest that POX represents a strong component of the defence mechanisms in nodules of resistant M. truncatula lines, where it could be involved in reinforcing the cell wall barrier. The stimulation of SOD activity is also a key mechanism in maintaining nodule integrity via controlling ROS overproduction when counteracting fungal attacks.