Behavior of three cereals cultivated in Tunisia under saline constraints and cationic homeostasis between Sodium and Potassium

Abstract

The accelerated rate of climate change exceeds the capacity to create new varieties that are adapted to water and salt stresses. Understanding the mechanisms of tolerance in major crops is the most important step in any improvement program for abiotic constraints. Three main cereal species cultivated in Tunisia (durum wheat, bread wheat and barley) each represented by 2 most used varieties were tested under increasing levels of irrigation water salinity (water tap at EC = 0.662 dS.m -1 , water tap with 3 g of NaCl at EC = 2.14 dS.m -1 , water tap with 6 g/l of NaCl at EC = 4.9 dS.m -1 and water tap with 9g/l of NaCl at EC = 12.54 dS.m -1 ). The 6 genotypes were tested in the laboratory in Petri dishes to study the germination rate with the same salinity levels. The experiment was carried out the first week of December under semi-controlled conditions, in 8-liter pots filled with a mixture of manure and calcareous loamy-clay soil. The experimental design was a Split Plot with three replications.The level of salinity is the main factor and variety as secondary one. At 4 leaf stage, only one seedling per pot is left and salinity treatment was applied. Results showed that the germination rate is proportionally affected by the intensity of salinity stress, reaching 25% in UTQ and 36% in MLI at 12.54 dS.m -1 . The balance between RDM and SDM is in favor of the root system under salinity stress, although the R/S ratio is always less than the unit. On the other hand, cationic K + /Na + ratio is always greater than the unit indicating good selectivity of the cereals for K + . Potassium is preferentially accumulated in stems while the Na + is preferentially accumulated in roots. Three strategies for limiting the entry of Na + are identified according to the level of its accumulation at the roots, stems or the two organs together. Abstract The accelerated rate of climate change exceeds the capacity to create new varieties that are adapted to water and salt stresses. Understanding the mechanisms of tolerance in major crops is the most important step in any improvement program for abiotic constraints. Three main cereal species cultivated in Tunisia (durum wheat, bread wheat and barley) each represented by 2 most used varieties were tested under increasing levels of irrigation water salinity (water tap at EC = 0.662 dS.m -1 , water tap with 3 g of NaCl at EC = 2.14 dS.m -1 , water tap with 6 g/l of NaCl at EC = 4.9 dS.m -1 and water tap with 9g/l of NaCl at EC = 12.54 dS.m -1 ). The 6 genotypes were tested in the laboratory in Petri dishes to study the germination rate with the same salinity levels. The experiment was carried out the first week of December under semi-controlled conditions, in 8-liter pots filled with a mixture of manure and calcareous loamy-clay soil. The experimental design was a Split Plot with three replications.The level of salinity is the main factor and variety as secondary one. At 4 leaf stage, only one seedling per pot is left and salinity treatment was applied. Results showed that the germination rate is proportionally affected by the intensity of salinity stress, reaching 25% in UTQ and 36% in MLI at 12.54 dS.m -1 . The balance between RDM and SDM is in favor of the root system under salinity stress, although the R/S ratio is always less than the unit. On the other hand, cationic K + /Na + ratio is always greater than the unit indicating good selectivity of the cereals for K + . Potassium is preferentially accumulated in stems while the Na + is preferentially accumulated in roots. Three strategies for limiting the entry of Na + are identified according to the level of its accumulation at the roots, stems or the two organs together.