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.

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<0.05) except for anthocyanins (P>0.05). Significant correlations were found between carotenoids and chlorophylls a and b (r= 0.59, n=48; P<0.0001) and between lycopene and β-carotene (r=0.81, n=48; P<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.

Effect of seed coating on germination of Ciliate Medick [Medicago ciliaris (L.) All.] and Snail Medick [Medicago scutellata (L.) Mill.]

A study was conducted in the Seed Technology Laboratory of Department of Field Crops, Pasture and Forage Crops Section, Faculty of Agriculture of Ege University, Turkey. Aim of the study was to remove the seed coat hardness by various treatments of Ciliate and Snail Medick to enhance germination which is significant in terms of agronomical handicaps of sowing small seeded legumes under field conditions. Pre-sowing seed treatments (Control, scarification by sandpaper, acid treatment with 95.0-98.0% H2SO4 for 5-10-15 minutes and soaking in water for 24-48 hours) were practiced on these small seeded legumes. All observations and tests were conducted following ISTA regulations and notifications. Germination of tested seeds highly increased by acid treatment for 10-15 minutes duration, while scarification treatment provided favorable germination rates.

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.