Role of seed priming in adaptation of horticultural crops to salt stress

Salt accumulation in the soil can represent severe threat to ecosystems by strongly affecting plant growth and reproduction, as well as reducing the biodiversity and metabolism of soil microorganisms. Soil salinization affects at least 20% of irrigated soil worldwide; this phenomenon involves arid, semi-arid, and sub-humid areas, leading to an irreversible degradation of the soil, called desertification. In recent years, several approaches were used to improve plant tolerance to salt stress, such as acclimation and seed priming. The latter is a pre-sowing treatment, consisting of soaking the seeds in a priming agent, followed by drying the seeds to avoid radicle emergence. A priming agent can provoke abiotic stress to seed, inducing a cross-tolerance to different abiotic stresses. While, an acclimation to stress can be obtained by a gradual exposure of the plant to stressful conditions, leading the plant to an adaptation to stress, thus to a better performance. The aim of this project is to verify the possibility to ameliorate salt tolerance in food crops, i.e. bean (Phaseolus spp.) and tomato (Solanum lycopersicum L.). Both tomatoes and beans are glycophytes, very sensitive to salt stress, which not only compromise their growth but also their yields, causing huge economic loss. To improve the tolerance of these crops, seed priming treatments were applied, and the effects of the different priming solutions were compared. Following the application of priming protocol, seed germination tests allowed the selection of the best priming treatments. Beans and tomato plants, either primed or not primed, were exposed to saline conditions and stress responses were determined. The salt stress responses were studied by quantifying the concentrations of photosynthetic pigments, phenolic compounds and proline. Enzymatic antioxidant activities were detected. Finally, the activation of the signalling pathway, in response to salt stress, was verified by measuring the intracellular Ca2+ leve