Consistent differences among wheat cultivars in osmotic adjustment and their relationship to plant production

Osmotic adjustment (OA) is generally considered an important component of drought resistance. Several reports by J.M. Morgan [Morgan, J.M., 1983. Osmoregulation as a selection criterion for drought tolerance in wheat, Aust, J, Agric, Res. 34, 607-614; 1992, Osmotic components and properties associated with genotypic differences in osmoregulation in wheat, Aust. J. Plant Physiol. 19, 67-76; 1995. Growth and yield of wheat lines with differing osmoregulative capacity at high soil water deficit in seasons of varying evaporative demand. Field Crops Res. 40, 143-152; Morgan, J.M,, Condon, A.G., 1986. Water-use, grain yield and osmoregulation in wheat. Aust. J. Plans Physiol, 13, 523-532] from Australia concluded that consistent genetic differences in OA existed among wheat cultivars and that high OA cultivars tended to yield better than low OA cultivars under drought stress. Our study was performed to assess his results with his and other genetic materials. Two of Morgan's spring wheat lines with high OA ('H.Osm-134') and low OA ('L.Osm-136') capacity in addition to eight other diverse spring wheat cultivars were tested for OA and plant production when grown in small plots under a rain exclusion shelter at Bet Dagan, Israel in 1996. OA of five of these cultivars (including Morgan's lines) was also measured in two independent greenhouse tests in 1997 (Israel) and 1998 (Texas). The five cultivars differed significantly and ranked consistently for OA in all tests. No significant cultivar by test interaction for OA was revealed. OA was well correlated across cultivars between tests. The significantly higher OA capacity of H.Osm-134 as compared with L.Osm-136 was repeated in all tests. OA of all ten cultivars was positively correlated with biomass (r = 0.73; p = 0.02) and yield (r = 0.55; p = 0.09) under pre-flowering drought stress in the rain exclusion shelter. H.Osm-134 line performed significantly (p less than or equal to 0.05) better than L.Osm-136 line for both biomass and yield under drought stress. We therefore support Morgan's results and conclude that consistent differences in OA exist among wheat cultivars and that these differences can be associated with plant production under pre-flowering drought stress. (C) 1999 Elsevier Science B.V. All rights reserved.