COMPARATIVE RESPONSE OF CULTIVATED AND WILD BARLEY SPECIES TO SALINITY STRESS AND CALCIUM SUPPLY

Foxtail barley (Hordeum jubatum L.), a wild species that can inhabit highly saline environments, may have more potent salt-tolerance genes than commercial barley (H. vulgare L.). The objective of this study was to compare the growth and ion relations of the commercial cultivar Harrington with foxtail barley under saline conditions, to determine whether a differential response to salinity stress exists between these species. Seedling performance was evaluated as a function of increasing concentrations of Na2SO4, MgSO4, and CaCl2 (within the electrolyte conductivity range of 0.26 to 1.38 S m-1) and the Ca mole fraction (Ca(mf)) of salt treatments in solution culture experiments. The Ca(mf) of the salt treatments, defined as the molar ratio of Ca/(Ca + Na + Mg), was maintained at 0.02 or 0.09. Salt treatments at a Ca(mf) of 0.02 significantly reduced leaf area, shoot growth, root growth, and the root-to-shoot ratio (R/S) of Harrington seedlings relative to foxtail barley. Growth of Harrington seedling improved substantially when the Ca(mf) was increased from 0.02 to 0.09. The two genotypes differed significantly in root weight and R/S under saline conditions; these differences were independent of the Ca(mf). Evaluation of root and shoot tissue ion contents revealed that H. jubatum seedlings accumulated less Na from the medium than Harrington and preferentially compartmentalized Na in root rather than shoot tissue. The wild species maintained higher levels of Ca, had more favorable K/Na ratios, and maintained higher R/S levels of SO4 than Harrington. Differences between H. jubatum and Harrington in root and shoot ion accumulation suggest that membrane permeability and selectivity properties are controlled by both genotype and Ca supply.