Growth and Yield of Barley Isopopulations Differing in Solute Potential 1

The active accumulation of solutes by osmotically stressed plants is thought to be an adaptive response that increases the ability of drought‐ or salt‐stressed plants to maintain leaf water content, turgor, and possibly growth. In an earlier study we developed two barley ( Hordeum vulgare L.) isopopulations differing in solute potential (ψ s ), and these isopopulations were characterized for their response to salt stress in the growth chamber. At each stress level tested, the low‐ψ s population had about 0.1 MPa lower ψ s . In the present study we used these isopopulations to test the effect of genetic differences in ψ s on growth in well‐watered and drought‐stressed conditions in the greenhouse and field. When grown in the greenhouse, the low ψ s population had a slower rate of leaf production and accumulated significantly less total aboveground dry matter by midanthesis than did the high‐ψ s population. This difference (up to 35%) was greatest in optimal environmental conditions (adequate water, high irradiance, warm temperatures) and decreased in less favorable environments. The growth differences were not associated with differences in partitioning of dry matter to the leaves or differences in water use efficiency. The growth disadvantage of the low‐ψ s population was also observed for grain yield (11–44%) and total aboveground biomass production (10–25%) under dryland and irrigated conditions in multisite field trials. Thus the development of a barley isopopulation with constitutively lower ψ s resulted in a reduction in yield potential.