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Background: Salinity is one of the major abiotic stresses affecting plant production in arid and semi-arid regions. It causes reduction of cultivable area and combined with other factors, presents a serious threat to food stability in these areas. Context: In front of this problem, the selection of salt tolerant species and varieties remains the best economic approach for exploitation and rehabilitation of salt-affected regions. Objective: The purpose of this study was to assess and compare the seed germination response of six Acacia species under different NaCl concentrations in order to explore opportunities for selection and breeding salt tolerant genotypes. Methods: The salinity effect was examined by measuring some agro-morphological parameters in controlled growth environment using five treatment levels: 0, 100, 200, 300 and 400 mM of NaCl. Results: The analyzed data revealed significant variability in salt response within and between species. All growth parameters were progressively reduced by increased NaCl concentrations. Growth in height, leaf number and total plant dry weight were considered as the most sensitive parameters. However, the growth reduction varied among species in accordance with their tolerance level. It is important to note that all species survived at the highest salinity (400 mM). Whereas A. horrida and A. raddiana were proved to be often the best tolerant, they recorded the lowest reduction percentage at this stage. Conclusion: The genetic variability found in the studied species at seedling stage may be used to select genotypes particularly suitable for rehabilitation and exploitation of lands affected by salinity., Comment: in French

Objective: The purpose of this study was to assess and compare the seed germination response of six Acacia species under different NaCl concentrations in order to explore opportunities for selection and breeding salt tolerant genotypes. Methodology: Germination of seeds was evaluated under salt stresses using 5 treatment levels: 0, 100, 200, 300 and 400 mM of NaCl. Corrected germination rate (GC), germination rate index (GRI) and mean germination time (MGT) were recorded during 10 days. Results: The results indicated that germination was significantly reduced in all species with the increase in NaCl concentrations. However, significant interspecific variation for salt tolerance was observed. The greatest variability in tolerance was observed at moderate salt stress (200 mM of NaCl) and the decrease in germination appeared to be more accentuated in A. cyanophylla and A. cyclops. Although, A. raddiana, remains the most interesting, it preserved the highest percentage (GC = 80%) and velocity of germination in all species studied in this study, even in the high salt levels. This species exhibited a particular adaptability to salt environment, at least at this stage in the life cycle and could be recommended for plantation establishment in salt affected areas. On the other hand, when ungerminated seeds were transferred from NaCl treatments to distilled water, they recovered largely their germination without a lag period and with high speed. This indicated that the germination inhibition was related to a reversible osmotic stress that induced dormancy rather than specific ion toxicity. Conclusion: This ability to germinate after exposure to higher concentrations of NaCl suggests that studied species, especially the most tolerant could be able to germinate under the salt affected soils and could be utilized for the rehabilitation of damaged arid zones., Comment: 9 pages, 3 figures

Wild populations of Medicago ciliaris and Medicago polymorpha were subjected to four salt treatments 0, 50, 100 and 150 mM NaCl, plant growth and proline concentration in leaves were assessed. The analyzed data revealed significant variability in salt response within and between the two species, depending on the salinity level. It was found that high NaCl concentrations affected all the growth parameters. However, the reduction was more important at higher NaCl concentrations and the highest reduction was obtained for the populations of Medicago polymorpha where it reached around 90% in root length at 150 mM NaCl for Pmar. The Tunisian population of Medicago ciliaris, prospected on soils affected by salinity, was the best tolerant in all ecotypes studied in this work. This population, exhibits a particular adaptability to salt environment at both germination and seedling stage. Furthermore, the correlation among the studied plants sensitivity and leaf proline concentration showed that high proline contents were related to their reactivity to salt. Consequently, it appeared that proline biosynthesis occurred presumably as a consequence of disturbance in cell homoeostasis and reflected poor performance and greater damage in response to salt stress. These findings indicated that this osmolytes content may be used as another useful criterion to differentiate salt-tolerant from salt sensitive plant in annual medics., Comment: 9 pages, 2 figures

The present study, investigated some reproductive and fertility parameters in some wild populations, originating from the North Tunisia (4 populations of Medicago ciliaris and 3 populations of Medicago intertexta). Previous finding revealed that these species are genetically distinct and easily recognized by the number of flowers per inflorescence and pod dimensions. However, biometrical traits and isozyme patterns intermediacy between these two species had detected the existence of a potential spontaneous interspecific hybrid originating from Sedjnane locality in Tunisia. Indeed, the present work has shown significant decrease of pollen fertility and seed production for this population when compared to the others(pollen viability 75%, pollen germinability 8% and pod production=9%). These results suggested a possible natural interspecific hybrid and confirming introgressive hybridization possibility between M. intertexta and M. ciliaris.