Medicago Ciliaris Research Articles

Combined effects of salinity and soil drying on growth, water, status, and photosynthesis in Medicago ciliaris and Medicago polymorpha

Combined effects of salinity and soil drying on growth, water, status, and photosynthesis in Medicago ciliaris and Medicago polymorpha

Variability in Responses to Phoma medicaginis Infection in a Tunisian Collection of Three Annual Medicago Species

Spring black stem and leaf spot, caused by Phoma medicaginis, is an issue in annual Medicago species. Therefore, in this study, we analyzed the response to P. medicaginis infection in a collection of 46 lines of three annual Medicago species (M. truncatula, M. ciliaris, and M. polymorpha) showing different geographic distribution in Tunisia. The reaction in the host to the disease is explained by the effects based on plant species, lines nested within species, treatment, the interaction of species × treatment, and the interaction of lines nested within species × treatment. Medicago ciliaris was the least affected for aerial growth under infection. Furthermore, the largest variation within species was found for M. truncatula under both conditions. Principal component analysis and hierarchical classification showed that M. ciliaris lines formed a separate group under control treatment and P. medicaginis infection and they are the most vigorous in growth. These results indicate that M. ciliaris is the least susceptible in response to P. medicaginis infection among the three Medicago species investigated here, which can be used as a good candidate in crop rotation to reduce disease pressure in the field and as a source of P. medicaginis resistance for the improvement of forage legumes.

Impact of Biochar Application at Water Shortage on Biochemical and Physiological Processes in Medicago ciliaris.

The application of biochar is mostly used to improve soil fertility, water retention capacity and nutrient uptake. The present study was conducted in order to study the impact of biochar at water deficiency conditions on the physiological and biochemical processes of Medicago ciliaris seedlings. Seedlings were cultivated under greenhouse conditions in pots filled with a mixture of soil and sand mixed in the presence or absence of 2% biochar. Plants of uniform size were subjected after a pretreatment phase (72 days) either to low (36% water holding capacity, water potential low) or high soil water potential (60% water holding capacity, water potential high). Pots were weighed every day to control and maintain a stable water holding capacity. In Medicago ciliaris, drought led to a significant reduction in plant growth and an increase in the root/shoot ratio. The growth response was accompanied by a decreased stomatal conductance and a reduction of the net CO2 assimilation rate and water use efficiency. The associated higher risk of ROS production was indicated by a high level of lipid peroxidation, high antioxidant activities and high proline accumulation. Soil amendment with biochar enhanced the growth significantly and supported the photosynthetic apparatus of Medicago ciliaris species by boosting chlorophyll content and Anet both under well and insufficient watered plants and water use efficiency in case of water shortage. This increase of water use efficiency was correlated with the biochar-mediated decrease of the MDA and proline contents in the leaves buffering the impact of drought on photosynthetic apparatus by increasing the activity of enzymatic antioxidants SOD, APX, GPOX and GR and non-enzymatic antioxidants, such as AsA and DHAsA, giving the overall picture of a moderate stress response. These results confirmed the hypothesis that biochar application significantly reduces both the degree of stress and the negative impact of oxidative stress on Medicago ciliaris plants. These results implied that this species could be suitable as a cash pasture plant in the development of agriculture on dry wasteland in a future world of water shortages.

Genetic Variation in Responses to Salt Stress in Tunisian Populations of Medicago ciliaris

Soil salinity is one of the most serious environmental factors affecting crop productivity around the world. We used a morpho-physiological approach to investigate the salt responses of four Tunisian natural populations of Medicago ciliaris. Forty-six lines of M. ciliaris were grown under a control treatment and 100 mM NaCl. We measured 11 quantitative traits of shoot and root growth during harvest. An analysis of variance showed that the variations in salt response can be explained by the effects of the population, line, treatment, and interactions between the population and treatment and the line and treatment. Most of the measured traits showed significant differences between the studied populations under the control treatment and salt stress. High to moderate broad-sense heritabilities (H2) were noted for most of the parameters under the control treatment and salt stress, implying that salt tolerance is highly heritable. Most correlations between the measured traits under the two treatments were positive, of which the strongest correlations were recorded between characteristics related to development. The 46 studied lines formed three groups in both conditions, while their genetic structure was dependent on the treatment factor. The results from this study can provide a basis for identifying and breeding salt-tolerant lines of M. ciliaris.

Genetic structure, differentiation, and slight evidence for no selective neutrality of some SSR markers in populations of Medicagociliaris (L.) Krock and Medicagointertexta (L.) Mill species

Medicago ciliaris (L.) Krock and Medicago intertexta (L.) Mill are most often found in saline regions and are considered as potential resources for genes related to salinity resistance. To explore the genetic diversity of these two species by mean of nrSSR (simplesequence repeats) markers, 11 accessions originated from different regions in north of Africa and Middle East were chosen. Ten among 14 markers turned out to be polymorphic and gave 72 alleles. Eight markers were very informative with PIC values > 0.5, and three of them were found to be nonneutral. Allelic richness was limited with an average number of alleles per locus of 2.7. All populations have a significant heterozygous deficit evidenced by both observed heterozygosity rates (null for most populations) and multilocus fixation index estimates. A strong differentiation between populations was highlighted by FST (0.805) and GST (0.919) values. Low values of gene flow (0.01-0.38) revealed a very weak gene exchange between populations regardless of the proximity of their sites of origin. The total variability breakdown by analysis of molecular variance (AMOVA test) showed a preponderance of interpopulation component (73%-72%) with respect to intrapopulation one (18%), mainly due to the mating system. Relationship analysis performed by NJ tree representation trends to place M. ciliaris as an ancestor and M. intertexta as a derivative. The two populations from the Sebkha site, characterized by the highest variability and more private alleles, constitute an ideal reservoir of genes for tolerance to salinity. Significant genetic diversity in the two aforementioned species is encouraging for their conservation

Comparing Salt Tolerance at Seedling and Germination Stages in Local Populations of Medicago ciliaris L. to Medicago intertexta L. and Medicago scutellata L.

Salt stress is one of the most serious environmental stressors that affect productivity of salt-sensitive crops. Medicago ciliaris is an annual legume whose adaptation to agroclimatic conditions has not been well described. This study focused on the salinity tolerance of M. ciliaris genotypes compared to M. intertexta and M. scutellata in terms of plant growth, physiology, and biochemistry. Salt tolerance was determined at both germination and early seedling growth. Germination and hydroponic assays were used with exposing seeds to 0, 50, 100, 150, and 200 mM NaCl. Among seven genotypes of M. ciliaris studied, Pop1, 355, and 667, were most salt tolerant. Populations like 355 and 667 showed marked tolerance to salinity at both germination and seedling stages (TI ≤1, SI(FGP) > 0 increased FGP ≥ 20% and SI(DW) < 0 (DW decline ≤ 20%); at 100 mM); while Pop1 was the most salt tolerant one at seedling stages with (TI =1.79, SI(FGP) < 0 decline of FGP ≤ 40% and with increased DW to 79%); at 150 mM NaCl). The genotypes, 306, 773, and M. scutellata, were moderately tolerant to salt stress depending on salt concentration. Our study may be used as an efficient strategy to reveal genetic variation in response to salt stress. This approach allows selection for desirable traits, enabling more efficient applications in breeding methods to achieve stress-tolerant M. ciliaris populations.

Author's Correction: Stress Tolerance and Symbiotic and Phylogenic Features of Root Nodule Bacteria Associated with Medicago Species in Different Bioclimatic Regions of Tunisia.

Thirty two rhizobial isolates were obtained from different bioclimatic regions of Tunisia using as trap plants, Medicago sativa, Medicago ciliaris, Medicago polymorpha and Medicago minima. To study their diversity and characterize them in relation to Mediterranean conditions, abiotic stress resistance, symbiotic properties and genetic diversity in terms of 16S rRNA and nodA sequences were assessed. Five isolates from M. sativa, three from M. ciliaris and three from M. minima could grow at 45°C. Only two isolates from M. sativa grew at 4% NaCl. The most stress tolerant isolates were obtained from arid soils. A phylogenetic analysis of 16S rRNA genes revealed 29 isolates to be closely related to Ensifer including one (Pl.3-9) that showed a 16S rRNA sequence similar to that of Ensifer meliloti and nodA sequence similar to that of Ensifer medicae. However, three isolates were categorized into Agrobacterium containing the nodA of Ensifer. Furthermore, these isolates developed nodules on original hosts. The results for the four isolates suggest horizontal gene transfer between the species.

Comparative analysis of antioxidant and secondary metabolites contents in eight populations of Medicago ciliaris L.

1 ABSTRACT To identify the suitable genetic resources of forage legumes for animal feeding, the characterization of their chemical and biochemical composition is crucial since forage quality is a limiting factor which affects animal health and performance and consequently human health. In this context, this study carried out for the first time the analyses of the antioxidant compounds and the secondary metabolites (total phenols and tannins and saponins) in whole fresh biomass, flowers and stems of eight populations of Medicago ciliaris L (echinus Medicago) collected in different bioclimatic areas of north Tunisia. The analysis of variance showed significant differences between populations for all parameters (P&lt;0.05) except for anthocyanins (P&gt;0.05). Significant correlations were found between carotenoids and chlorophylls a and b (r= 0.59, n=48; P&lt;0.0001) and between lycopene and β-carotene (r=0.81, n=48; P&lt;0.0001). Multivariate analysis showed that populations 306 and 326 had the highest contents of chlorophyll a and carotenoids while Pop3 had the highest content of lycopene, β-carotenes, saponines and total tannins. These populations will be integrated in a breeding program for quality improvement of forage and will serve for grazing of pods and straw in summer and grazing of green biomass in winter and spring accordingly to their richness in antioxidant compounds.

Changes in growth and oxidative response of leaves and nodules in Medicago ciliaris during salt stress recovery

In the present study, we exposed Medicago ciliaris isolated from a saline sebhka and growing symbiotically with Sinorhizobium medicae to 100 mM of NaCl and followed this stress by a recovery period (complete NaCl withdrawal from the root medium for two or one weeks). This experiment was conducted in order i) to check whether a reduction in growth and nitrogen fixation could be reversed by alleviating salt stress and ii) to determine specific changes related to salt-induced growth and nitrogen fixation decline. Salt stress reduced growth of all organs (particularly nodules), leaf area, photosynthetic activity and nitrogen fixation. The depressive effect of salt was not linked to osmotic stress. The removal of saline conditions restored growth of all organs after 2 weeks of recovery, with aerial organs recovering quickly after 1 week. Both photosynthetic and nitrogen fixation recovered only after a 2 week period of recovery. Salt stress in these saline-tolerant plants was accompanied by oxidative damage (electrolyte leakage), which was more accentuated in nodules in comparison with leaves. The observed recovery in growth, nitrogen fixation and photosynthesis was mainly linked to a preferential preservation of shoots growth owing to the maintenance of SOD activity (namely the isoforms A2 and A3); such maintenance would allow higher photosynthetic activity permitting an adequate supply of nodules with photoassimilates and thus facilitating stress withstand.

Comparison of genetic diversity among Medicago ciliaris populations prospected from highly salted region (Oran Great Sebkha) using morphological pod descriptors of IBPGR and SDS-PAGE markers

Comparison of genetic diversity among Medicago ciliaris populations prospected from highly salted region (Oran Great Sebkha) using morphological pod descriptors of IBPGR and SDS-PAGE markers

Diversity of Salt Tolerance During Germination in Medicago ciliaris (L.) and Medicago polymorpha (L.)

Variability of salt tolerance in eight wild populations of two annual Medicago species (Medicago ciliaris and Medicago polymorpha) was evaluated at germination stage using tree treatments of salinity: 50, 100 and 150 mM of NaCl. Results showed that germination is clearly affected by high salt stress; their germination rate doesn’t exceed 7% at 150 mM. The greatest variability in tolerance was observed at moderate salt stress (50 mM of NaCl) and the decrease in germination seems to be more accentuated in Medicago polymorpha than Medicago ciliaris. Whereas, the Tunisian population of Medicago ciliaris was the best tolerant in all ecotypes studied in this work. This population prospected on soils affected by salinity, exhibits a particular adaptability to salt environment, at least at this stage in the life cycle. This intra-specific variation in salt tolerance may be used to select genotypes particularly suitable for cultivation on lands relatively affected by salinity. On the other hand, when ungerminated seeds from NaCl treatments were transferred to distilled water, they recovered largely their germination at all the populations studied after only 2 days. This, indicate that the germination inhibition was related to osmotic stress rather than ion toxicity. In addition, seed germination in all populations tended to be extremely rapid than that observed in distilled water which indicate that this pretreatment raises dormancy.

English

Medics are annual forages very interesting in pastures of Mediterranean and steppes rangelands. Such as other leguminous, they are subject to dormancy which delay and reduce germination. The response of these species (Medicago polymorpha, Medicago intertexta, Medicago ciliaris, Medicago truncatula, Medicago muricoleptis) to mechanical, physical and chemical scarification, applied for break dormancy, had been studied. Germination is almost full (reaching 100%) is fast (24 h) after scarification with sand-paper, which demonstrates that dormancy is exclusively imposed by teguments of the grain. Soaking in boiled water (20 s by population), passing through sulphuric acid during 5 min and 180 mn, passing in freezer and in refrigerator (respectively 2 h and 5 days), in drying oven at 115°C during 20 mn eliminates partially dormancy. However, passing through ovine digestive tract followed by germination test possesses the same effect as the witness. In exposure in ultra-low temperature at 196°C (liquid nitrogen) during 25 mn improves germination and grains germination speed to all quoted species which is comparable to scarified grains results by sand-paper. Keys words: Scarification, medics, populations, germination, dormancy.

Pheno-morphological variation, genetic diversity and population structure of Tunisian Echinus Medic (Medicago ciliaris L.).

Medicago ciliaris L., considered as a valuable genetic resource, is a good candidate for the improvement of marginal or degraded lands with low fertility or high salinity. In this study, the pheno-morphological and genetic diversity were investigated in 14 Tunisian populations of M. ciliaris for the first time. Fourteen morphological traits showed significant differentiation between populations and high levels of diversity. Two amplified fragment length polymorphism primer combinations (E-AGC/M-CAA; E-AAG/M-CTG) were analyzed using an automated capillary electrophoresis system. A total of 528 loci were generated, of which 54% were polymorphic. Allelic polymorphism ranged from 0.02 to 0.5. Significant variation between populations was found for gene diversity, mean number of alleles per locus and Shannon index for which mean values were 0.17, 0.26, and 1.57, respectively. Analysis of molecular variance revealed a high rate of genetic variation within populations. Principal component analysis and genotypic clustering discriminated M. ciliaris populations according to their geographical origin. M. ciliaris clustered into three main groups. The first group was associated with high inland and cold areas, the second was defined by low areas with mild winters while the third described low coastal areas. Similarity of morphological and molecular results indicated that either markers could be used for the study of genetic diversity in this species.

Aerials and Roots Vegetative Tissues Differ in Guaiacol Peroxidases Responses to Cold Stress in Two Contrasting &lt;i&gt;Medicago ciliaris&lt;/i&gt; Populations

Effect of cold on antioxidant responses in aerial (shoots and leaves) and roots tissues of two contrasting accessions of M. ciliaris Krockers (Cil 126, tolerant and Cil 123, sensible) were investigated. Ten-day-old grown seedlings were subjected at different periods of cold acclimation (4°C) 2, 4, and 6 days. Peroxidases (POD) (EC 1.11.1.7) activities and isoenzymes expression of plantlets treated and control (23°C) of the aerial (shoot+leaves) and root vegetative tissues were carried. Global peroxidase activity under low temperature stress was higher in tolerant ecotype than sensible one. The same trend was also observed at expressed isoenzymes. On the other hand, whether in tolerant or sensitive, activity and isoenzymes peroxidase was more pronounced at the roots than in aerials tissues system.

Nutrient uptake and use efficiencies in Medicago ciliaris under salinity

ABSTRACTSalt-induced responses of Medicago ciliaris was studied under controlled conditions. Twenty-two-day old seedlings were cultivated for one month in a nutrient medium added or not with 75 mM sodium chloride (NaCl). Our results showed that this species is relatively salt-tolerant since the whole biomass production of salt-treated plants was affected a little (−30%) as compared to the control. The slight salt effect was mainly nutritional and concerned both macro potassium, calcium and magnesium (K, Ca, and Mg) and micro-nutrients iron (Fe). K and Fe uptake efficiencies were more affected than those of Ca and Mg. Nevertheless, M. ciliaris was able to counterbalance this impact by increasing both K and Fe use efficiencies. The enhancement of K use efficiency could be due in part to the plant aptitude to accumulate sodium (Na+) ions within its shoot tissues and to use them for osmotic adjustment. This “includer” behavior allowed M. ciliaris to maintain an adequate water status under saline conditions.

Phenotypic and symbiotic characterization of rhizobia isolated from &lt;em&gt;Medicago ciliaris&lt;/em&gt; L. from Algeria

Several phenotypic tests were used in this study to determine the biodiversity of rhizobial strains nodulating Medicago ciliaris L. Phenotypic characteristics of thirty-seven rhizobia strains isolated from root nodules of Medicago ciliaris L. growing in soils collected from Zerizer (north eastern Algeria) were studied. Tolerance to salinity, high temperatures, acid and alkaline pHs, drought and antibiotics and symbiotic and cultural characteristics allowed the description of a wide physiological diversity among tested isolates. Thirteen isolates from the total could grow at 458C. Only six isolates grew at 4% NaCl. Furthermore, the isolates that showed tolerance to salinity stress also showed tolerance to water stress, indicating direct relationships between these two physiological pathways. High saltand water stress-tolerant strains were isolated and tested for their ability to fix biological nitrogen. Seven isolates were phenotypically categorised as Agrobacterium.

Phenotypic and symbiotic characterization of rhizobia isolated from Medicago ciliaris L. from Algeria

Phenotypic and symbiotic characterization of rhizobia isolated from Medicago ciliaris L. from Algeria

English

The present study estimated the diversity of seed storage salt-soluble proteins of Algerian populations of Medicago ciliaris species, for understanding biochemical and molecular features involved in response during plant stress adaptation. Eleven patterns of M. ciliaris populations with two moderate sensitive ecotypes to NaCl, two reference genotypes and seven prospecting populations near and far from a strongly salted area (Sebkha of Oran) were investigated by one dimensional electrophoresis SDS-PAGE. The results show that the proteins profiles were very similar with 10 to 12 bands profiles about all populations, after electrophoresis in denaturing conditions; but an 80 kDa band was visible only on population from Sebkha origin, where the salt content in the soil is the highest one. It appears that, this globulin protein is related to salt tolerance and could be used as SDS-AGE markers for differentiating between tolerating and sensible M. ciliaris populations to salt stress. &nbsp; Key words: Oran Great Sebkha, annual Medicago ciliaris, seed storage salt-soluble proteins, sodium dodecyl sulfate- poly acrylamide gel electrophoresis (SDS-PAGE) markers.

English

Phenotypic characteristics of 37 rhizobia strains isolated from root nodules of Medicago ciliaris L. growing in soils collected from Zerizer (North Eastern Algeria) were studied. Tolerance to salinity, high temperatures, acid and alkaline pHs, drought and to antibiotics as well as symbiotic and cultural characteristics allowed the description of a wide physiological diversity among tested isolates. Thirteen (13) isolates from the total could grow at 45°C. Only six isolates grew at 4% NaCl. Furthermore, the isolates which showed tolerance to salinity stress also showed tolerance to water stress, indicating direct relationships between these two physiological pathways. High salt and water stress tolerant strains were isolated and tested for their ability to biological nitrogen fixation. However, seven isolates were categorized into Agrobacterium. Key words: Medica gociliaris, stress tolerance, Algeria, symbiotic properties.

Iron Deficiency Tolerance at Leaf Level in &amp;lt;i&amp;gt;Medicago ciliaris&amp;lt;/i&amp;gt; Plants

Iron deficiency is an important environmental factor restricting plant productivity. Selecting tolerant genotypes is one of the possible ways to solve this problem. Many studies reported the effects of Fe deficiency on photosynthesis and anti-oxidative defense system. Yet, there is little information available on the use of these attributes as selective criteria. In the present study, we aim to determine some physiological and biochemical traits conferring Fe deficiency tolerance at leaf level in two lines of Medicago ciliaris. Our results showed that Fe deprivation had a lowering effect on photosynthesis (chlorophyll, photosynthetic electron transport activity and chlorophyll fluorescence) in both lines studied. However, the sensitive line TN8.7 was more affected. Hydrogen peroxide concentration was negatively correlated with the activities of antioxidant enzymes and with the concentration of some non-enzymatic antioxidant. The tolerant line TN11.11 was characterized by a more efficient antioxidant defense system in comparison with the sensitive line TN8.7. The main conclusion of this study is that photosynthesis and antioxidant defense system could be used as physiological and biochemical indicators of Fe deficiency tolerance in Medicago ciliaris plants.