Yield and yield component responses of bread and durum wheat to PGRs under drought stress conditions in field and greenhouse

Application of plant growth regulators (PGRs) could be one of the methods to compensate for the harmful effects of drought stress, as the most important factor limiting wheat yield. To examine the effect of two PGRs; cycocel (CCC) and salicylic acid (SA) on grain yield and its components of a bread (Roshan) and a durum (Yavarous) wheat under different water regimes [normal (as control), moderate and severe drought], field and greenhouse experiments were carried out at the Research Field and Greenhouse of College of Agriculture, Shiraz University during 2009-2010 growing season. Field and greenhouse experiments were organized as a split factorial based on randomized complete block design and completely randomized design, respectively. Results showed that drought stress caused remarkable reductions in ear length, grain number per spikelet, grain and spikelet number per ear, grain yield, biological yield and harvest index. The highest and lowest effects of drought stress were observed in biological yield and 1000- grain weight, respectively. PGRs increased ear length, grain number per spikelet, grain and spikelet number per ear, 1000- grain weight as well as the grain yield. SA and CCC application was associated with enhancement and reduction in biological yield, respectively. Harvest index was increased in CCC treated plants. Responses of Roshan cultivar yield and its components to drought stress and both PGRs application were more than Yavarous. Also it appeared that Roshan cv. had more grain yield, and Yavarous had higher resistance to drought stress. Although drought stress caused reductions in most yield components of wheat, PGRs application could alleviate a part of these harmful effects. Therefore application of these PGRs, especially CCC, is recommended under drought stress conditions.