Water Relations in Winter Wheat as Drought Resistance Indicators

Although drought is recognized as an important limitation to wheat ( Triticum aestivum L.) production in many regions, drought resistance selection techniques are not adequately developed. In 1984–1985 and 1985–1986, field experiments were conducted in Stillwater, OK, to determine potential drought resistance parameters and their inheritance in winter wheat. Single plants of drought resistant ‘TAM W‐101’ and drought susceptible ‘Sturdy’, their F 1 and F 2 progeny, and backcrosses of the F 1 to each parent were evaluated under a rain shelter. Tiller number was recorded throughout the growing season. As stress developed during reproductive development, water potential (WP), solute potential (SP), turgor potential (TP), relative water content (RWC) were measured at 7‐ to 10‐d intervals on single leaves until tlag leaf senescence. Tiller number and growth rate were similar among the six populations. Water potential, WP components, and RWC declined with increasing drought stress, but no significant differences among populations were found, in WP, SP, or TP. Relative water content differed significantly among populations under increasing drought stress. TAM W‐101 maintained a higher RWC under drought conditions than Sturdy, and had a longer grain‐filling period. Comparison of the RWC values among populations indicated that differences were controlled predominantly by genes with additive effects. Narrow‐sense heritability ( h 2 ) of RWC increased as drought stress intensified and reached a maximum value of 0.64 1 wk prior to flag leaf senescence. With this high h 2 , RWC shows promise as a selection criterion for drought resistance in winter wheat.