Influence of Water Stress and Plant Growth Regulators on Yield and Development of Two Durum Wheat (Triticum turgidum L. var. durum) Cultivars

Water stress is a major factor limiting crop production in many regions of the world. There is evidence that plant growth regulators could be used to partially counteract environmental stresses and improve crop productivity. Greenhouse and field experiments were conducted at the University of Jordan Research Station during 2000/2001 growing season to examine the influence of mepiquat chloride (1,1-dimethyl piperidinium chloride) and ethephon (2-chloroethyl-phosphonic acid) on growth, yield and water use efficiency of two selected wheat cultivars (Triticum turgidum L. var. durum). In greenhouse pot experiments, seeds of Hourani and Petra cultivars were soaked with mepiquat chloride solution at the rate of 0, 250, 500, and 750 mg kg–1 seeds before sowing in one experiment while ethephon was sprayed at the rate of 0, 150, 300 g ha–1 at seedling and tillering stages in a second experiment. Plants were subjected to two moisture levels; optimum water (70-100% of field capacity) and water-stressed (30% of field capacity) for the entire growth period of the two cultivars. In field experiments, ethephon solutions were sprayed at the rate of 0, 150, 300, and 450 g ha -1 at seedling, tillering and stem elongation stages in one experiment. Other experiment seeds of both cultivars were soaked with mepiquat chloride solution at the rate of 0, 250, 500, 750 and 1000 mg kg –1 before sowing. Applications of mepiquat chloride and ethephon showed no influence on shoot to root ratio of wheat plants. Grain yield of both cultivars grown under optimum moisture and water-stressed conditions was increased with mepiquat chloride treatment. Ethephon treatment increased grain yield and harvest index of Hourani under optimum moisture conditions in both greenhouse and field experiments which might be attributed to the increase in the number of fertile tillers per plant. Water use efficiency of Hourani was improved only by mepiquat chloride treatment. Petra produced more grain yield by up to 40% than Hourani. Moreover, Petra had a higher number of fertile tillers and harvest index than Hourani