Abstract
Limited knowledge of the physiological basis of the detrimental effects of soil salinity on growth and yield of barley and the consequent lack of suitable screening traits are two reasons for the limited success of plant breeding in saline environments. We assessed the relationships between grain yield, carbon isotope discrimination (Δ), canopy temperature, stomatal conductance, and grain ash content in a set of barley cultivars grown in a soil salinity gradient imposed by a triple-line-source sprinkler system. A linear increase in soil salinity produced significant ( P<0.05) and linear decreases in grain yield and Δ, and increases in midday differential canopy temperature ( δT). For unit increase in soil solution electrical conductivity (ECss), Δ decreased by 0.2‰ and δT increased by 0.3°C. Increasing soil salinity from the control (non-saline) to a highly saline level (ECss=22 dS m −1) decreased leaf stomatal conductance by 65% and increased grain ash content by 11–29%. Grain yield and grain Δ of 34 barley cultivars were significantly ( r=0.58; P<0.01) correlated in non-saline conditions, suggesting that Δ is a useful indicator of yield potential in barley. However, there was no significant correlation between grain yield and grain Δ under highly saline conditions ( r=0.29; P>0.05). A multiple linear regression of Δ, stomatal conductance and grain ash content on grain yield was highly significant ( R 2=0.77, P<0.001) in non-saline conditions, but not in highly saline conditions. We concluded that none of the studied characters would be useful in screening for high yield under saline environments, and that grain yield under salt stress remains the only reliable means of identifying higher salt tolerance in barley.
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