Effect of sodium exclusion trait on chlorophyll retention and growth of durum wheat in saline soil

Six durum wheat genotypes with contrasting extents of sodium accumulation in leaves were used to assess the effects of sodium exclusion on leaf longevity and biomass production in saline soil. Leaf chlorophyll content, ion concentration, plant height, and dry biomass were measured at 3 salinity levels (1, 75, and 150 mM NaCl, with supplemental Ca2+). Yield and yield components were measured on 2 contrasting groups of genotypes. The low Na+ genotypes showed much longer chlorophyll retention than the high Na+ genotypes, the start of leaf senescence being prolonged by a week or more in the low Na+ genotypes. The difference was greatest at 75 mM NaCl. At ear emergence, the effects of salinity on biomass were less on the low Na+ than on the high Na+ genotypes at 75 mM NaCl, but there was no difference between groups at 150 mM NaCl. At maturity, salinity had a similar effect on biomass of both genotypes, at both 75 and 150 mM NaCl. Grain yield at 150 mM NaCl was equally reduced in both genotypes, being only 12% of controls. However, at 75 mM NaCl there was a significant yield difference between genotypes; yield of the high Na+ genotype was only 70% of controls, whereas yield of the low Na+ genotype was 88% of controls. The greater yield of the low Na+ genotype was due to enhanced grain number and grain weight in the tiller ears.