Horticultural crops response to salt stress: role of seed priming and acclimation

Salt accumulation in the soil and water resource scarcity can represent severe threats to agriculture 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 irreversible degradation of the soil, called desertification. In recent years, several approaches have been 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 the growth and reproduction 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 compromises their growth but also their yields, causing huge economic loss. Seed priming protocols with polyamines were applied in beans and tomato. Priming does not affect seed germination, nevertheless primed and germinated seeds did not survive when sown in saline soil. Therefore, we decided to test if acclimation would provide a better plant performance in saline conditions. Since the high level of sensitivity to salt was not overcome by acclimation, we further applied combined treatments, i.e. seed priming followed by acclimation. Plants, either primed or not, were acclimated by watering with saline solution twice a week. At the end of the experiments, the electrical conductivities (EC) of the soils were 0.45 dS/m (not saline soil) and 2.05 dS/m (saline soil). The EC of the latter was above the threshold of salt tolerance of both species. The effects of salinity on primed plants were negligible with respect to not primed ones. Overall, the results suggest the possibility to use both seed priming and acclimation as a tool to improve salt stress tolerance in tomatoes and beans.