Response of four spring wheat cultivars to drought stress

Identification and understanding of the mechanism of drought tolerance in wheat (Triticum aestivum L.) cultivars has long been a major goal of plant breeders. Our objective was to determine if leaf water potential, osmotic potential, yield, and yield components could be used to differentiate apparent drought tolerance among the cultivars. Four spring wheat cultivars (Giza 165, Gemmiza 1, Klassic, and SPHE3) from different geographic regions were grown in a greenhouse at 20/15 degrees C with 12 h of daylight augmented with artificial lighting and subjected to water stress imposed by withholding irrigation at different stages of growth. The three treatments were: no stress (W1); 10 d stress at tillering (W2); and 10 d stress at heading (W3). Water stress caused large differences for yield and yield components. For the W3 treatment, Giza 165, Gemmiza 1, and SPHE3 had yield decreases of 44%, 43%, and 18%, respectively, while Klassic had a yield increase of 4%. The average slopes of the turgor vs leaf water potential plots were 0.56 for Giza 165 and Gemmiza 1 vs 0.43 for Klassic and SPHE3 at heading. The difference between the two groups was statistically significant as determined by the 95% Tukey test. Stress applied at either tillering or heading gave similar results but effects were more pronounced when stress was applied at heading. It was not possible to determine if osmotic adjustment contributed to the differences between cultivars in response to water stress.