Seasonal Drought Response of Selected Wheat Cultivars1

Abstract

AbstractThe 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 (ψx), adaxial leaf diffusive resistance (R5), 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 ψx 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 H2O) which was less than half that of the irrigated controls (44 cm H2O). Late in the second season, ψx, decreased to as low as −47 bars in some treatments. Correlation between midday ψx and yield (absolute or percent of control) for individual cultivars were highly significant. The importance of full night ψx 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 ψx decreased to −7 bars. Further reduction of predawn ψx 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.