Effect of drought and salinity on carbon isotope discrimination in wheat cultivars

Four drought- and salt-tolerant wheat cultivars were grown in pots in a naturally lit glasshouse with two watering regimes (30 and 75% plant available water) and three salinity levels (8, 12 and 16 dS/m), a zero salinity treatment served as control. Carbon isotope discrimination (Δ) varied significantly (P < 0.001) among cultivars under well-watered and water-stressed conditions. Soil salinity produced a linear and significant (P < 0.001) decrease in Δ of all cultivars. Salinity × cultivars interaction for Δ was also significant (P < 0.05) under both watering regimes. The correlation between Δ of leaves and HI was positive (r = 0.61, P < 0.05) for salt-tolerant cultivars and negative (r = −0.63, P < 0.05) for drought-tolerant cultivars under well-watered conditions. Salt-tolerant cultivars showed a significant positive correlation (r = 0.71, P < 0.05) between HI and Δ of shoots under moisture-deficit conditions. Preliminary data indicated that measurements of Δ may prove to be a useful trait for selecting wheat cultivars with improved harvest index in salt-affected areas.