Understanding the salt tolerance mechanism in obligate halophytes provides valuable information for conservation and re-habitation of saline areas. Here, we investigated the responses of three obligate halophytes namely Arthrocnemum macrostachyum, Sarcocornia fruticosa and Salicornia europaea to salt stress (0, 100, 200, 400 and 600 mM NaCl) during their vegetative growth with regard to biomass, ions contents (Na+, K+ and Ca+2), chlorophyll contents, carotenoids, phenolic compounds, flavonoids, and superoxide dismutase, peroxidase and esterase activities. S. europaea showed the lowest biomass, root K+ content, Chl a/b ratio, and carotenoids under salinity. This reduction of biomass is concomitant with the increase in proline contents and peroxidase activity. On the other hand, the promotion of growth under low salinity and maintenance under high salinity (200 and 400 Mm NaCl) in A. Macrostachyum and S. fruticosa are accompanied by an increase in Chl a/b ratio, carotenoids, phenolics contents, and esterase activity. Proline content was decreased under high salinity (400 and 600 mM NaCl) in both species compared to S. europaea, while peroxidase showed the lowest activity in both plants under all salt levels except under 600 mM NaCl in Arthrocnemum macrostachyum compared to S. europaea. These results suggest two differential strategies; (1) the salt tolerance is due to activation of antioxidant enzymes and biosynthesis of proline in S. europaea, (2) the salt tolerance in A. macrostachyum, S. fruticosa are due to rearrangement of chlorophyll ratio and biosynthesis of antioxidant compounds (carotenoids, phenolics and flavonoids) which their cost seem to need less energy than activation of antioxidant enzymes. The differential behavior in halophytes of the same habitat confirms that the tolerance mechanism in halophytes is species-specific which provides new insight about the restoration strategy of saline areas.

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Zygophyllum coccineum is a facultative halophyte widely distributed in desert wadis and coastal areas in Egypt. Here, we investigated the influences of maternal habitat on tolerance to salt stress during germination and seedling growth under salinity (0, 100, 200, 400 mM NaCl) of three populations of Z. coccineum from a saline habitat (Manzala coast) and non-saline habitats (Wadi Houf and Wadi Asyuti). In all populations, seed germination started within two days in distilled water but germination indices were reduced significantly with salt level increase. Germination percentage was not significantly greater for seeds from non-saline habitats than for those from the saline habitat under moderate salinity (100, 200 mM NaCl), but only seeds from the saline habitat were able to germinate under high salt stress (400 mM NaCl). Germination recovery was greater for seeds from the saline habitat compared to non-saline populations. At the seedling level, the Manzala population showed the lowest inhibition of shoot length and leaf area under salinity (200 and 400 mM NaCl) compared to non-saline habitats. In the same context, the Manzala population had the maximum chlorophyll a content, superoxide dismutase and esterase activities under salinity compared to non-saline populations, but salinity had a non-significant effect on chlorophyll b between the three populations. Carotenoids were enhanced with the increase of salt levels in all populations. These results suggest the salt tolerance of Manzala population is derived from maternal salinity and adaptive plasticity of this species may play an important role in the wide distribution of Z. coccineum.

The difference in virulence of two standard strains in colonizing seedling hypocotyle and fruit exocarp suggested that multi-locus control of this trait. Whereas, Strain ATCC18099 was unable to infect uninjured cucumber and Zucchini fruits, both strains had high virulence against seedlings. The inheritance mode of this trait was studied by tetrad and random ascospore analysis with ascospores obtained from reciprocal crossings between ATCC18098 and ATCC18099. Segregation of MAT and perithecial color was also examined in both types of ascospore analyses. The results of tetrad analysis indicated 4:4 segregation for the high virulence associated with strain ATCC18098 in each tetrad, suggesting a Mendelian mode of inheritance. In random ascospore analysis, chi-square test supported that progeny with and without high virulence segregated in 1:1 in each cross and linkage analysis showed that such trait segregated independently from either MAT or perithecial color trait.