Seasonal Drought Response of Selected Wheat Cultivars 1

The relationship between seasonal plant water status and final yield as affected by cultivar is not well documented in wheat. In a 2‐year field experiment, plant water status measurements were used to compare the drought response of selected wheat cultivars. Yield, xylem pressure potential (ψ x ), adaxial leaf diffusive resistance (R 5 ), and soil water content (θ) were monitored. Twelve cultivars of Triticum aestivum L. em Thell and T. durum Desf., and two of Tritosecale wittmack were used. Genotypes with lower seasonal ψ x generally had higher percent yield reduction, when yield was expressed as a percent of irrigated controls. Water use during the observation period in the second season was similar for all droughted treatments and cultivars (about 17 cm H 2 O) which was less than half that of the irrigated controls (44 cm H 2 O). Late in the second season, ψ x , decreased to as low as −47 bars in some treatments. Correlation between midday ψ x and yield (absolute or percent of control) for individual cultivars were highly significant. The importance of full night ψ x recovery to near zero was apparent since for three cultivars studied intensively, 80% of the yield difference between nonstressed controls and stressed treatments had already accrued when pre‐sunrise ψ x decreased to −7 bars. Further reduction of predawn ψ x to −38 bars was associated with only an additional 20% of the yield loss. Observations of R, proved relatively insensitive to cultivar differences in these severely arid conditions.