A Technique for Assessing Seedling Emergence under Drought Stress1

Abstract

A procedure involving a cellulose acetate membrane separating a polyethylene glycol‐6,000 osmoticum from a germination medium of soil was modified for use as a plant‐selection tool. This technique avoided direct seed and osmoticum contact, allowed maintenance of a wide range of soil water potentials, and was capable of assessing emergence of large numbers of seedlings. This procedure was used to assess seedling emergence under drought stress of 120 lines of crested wheatgrass—Agropyron desertorum (Fisch. ex Link) Shult., A. cristatum (L.) Gaertn., and A. sibiricum (Willd.) Beauv. Significant differences in seedling emergence at two water stress levels occurred among the crested wheatgrass lines. The genetic variance as greater under the more severe drought stress. However, relative differences among lines were not consistent under the two drought stress regimes, as indicated by the highly significant progeny ✕ stress‐level interaction and the significant, but low, correlation between drought stress levels (r=0.40, 118 d.f.). Although opportunities for genetic improvement may be greater under the more severe moisture stress level, the environment of intended use must be considered during selection.