Effects of salinity and drought on growth, water use efficiency and sodium and potassium concentrations of two irrigated and rain-fed spring wheat genotypes

Abstract:
Introduction: The effect of drought and salinity stress in view of water deficiency are similar to each other, but under long term-salinity stress, in addition to drought stress the plant experiences increased osmotic and high ion stress. There are different levels of salinity (more than 38% of Golestan’s total land area is salt-affected) and various farming conditions (rain-fed and irrigation) in Golestan Province, Iran. The purpose of this study was to evaluate the growth, water use efficiency and sodium and potassium concentrations of plant in irrigated and rain-fed wheat genotypes (selected from the first year of the experiment).
Materials and methods: The experiment was under greenhouse conditions and was conducted to physiologically compare genotypes selected in the first year in a factorial arrangement with two irrigation regimes (5 and 75 % water lost from soil available water), four levels of soil salinity (0, 4.5, 6.5, and 8 ds/m) and two tolerant genotypes (selected from the first year) in a completely randomized design with three replications. The greenhouse is located in Gorgan city of Iran. Two genotypes selected from the first year of the experiment at moderate salinity (9 ds/m) and under rain-fed condition i.e. N- 87- 20 and Karim were the experimental material, respectively. In this experiment leaf area, number of stomata, sodium and potassium concentrations for leaf and stem, total water use from sowing to maturity, water use efficiency (WUE) for grain and biomass and yield were measured.
Results: The results showed that genotype n- 87- 20 had higher leaf area but lower stomata density than those of Karim. Genotype n- 87- 20 in 25% soil available water, i.e. drier condition had similar yield (1.20 vs. 1.16 gr/plant) to Karim. In the wetter condition the yield of N- 87- 20 was higher than Karim (2.00 vs. 1.64 gr/plant). In drier condition, Karim had higher WUE than in wet condition but for N- 87- 20 genotype, it was reverse and it had higher WUE in dry than in wet condition. The sodium concentration in stem was twice as bigger than that of leaf (0.58 and 0.32%, respectively) and with increase in unit salinity of soil to 8 ds/m sodium concentration in leaf and stem increased 0.068 and 0.025 %, respectively. There was not any difference between two genotypes for Na+/ k+ in leaf and stem but with an increase in soil salinity the Na+/ k+ for leaf and stem decreased.
Conclusion: N- 87- 20 was better genotype in irrigated conditions with no or moderate salinity stress and Karim was better genotype under rain-fed condition. Up to 8 ds/m of soil salinity Na+/k+ ratio could indicate the difference between genotypes.