Yield Response of Bread and Durum Wheat to Different Levels of Auxin and Cytokinin Application under Terminal Drought Stress Conditions

Drought stress is the most important factor restricting both growth and crop yield formation under arid and semi-arid conditions. In a field experiment, the effects of foliar application of growth regulators of auxin at three levels (0, 20 and 40 mg/L) and cytokinin at three levels (0, 50 and 70 µmol) at pollination stage on yield and yield components of a bread wheat (Shiraz cultivar) and durum wheat (Yavaros cultivar) under drought conditions (normal irrigation and irrigation cut-off at flowering stage) were investigated. This experiment was carried out at college of Agriculture, Shiraz University, Shiraz, Iran, during 2010-2011 as split-split factorial using complete randomized blocks design with three replications. The results showed that drought stress reduced number of grains per spike (25% for Shiraz and Yavaros cv), 1000-grain weight (14 and 30% for Shiraz and Yavaros cv respectively), number of grains per unitarea (30% for Shiraz and Yavaros cv), grain yield (15 and 35% for Shiraz and Yavaros cv respectively), biological yield (13 and 35% for Shiraz and Yavaros cv respectively) and wheat harvest index (15 and 27% for Shiraz and Yavaros cv respectively). Foliar application of auxin and cytokinin under normal irrigation improved grain yield and yield components. Therefore, it was concluded from this research that application of 40 mg/L auxin for bread wheat (Shiraz cv.) and 70 µmol cytokinin for durum wheat (Yavaros cv.) improved grain yield only under normal irrigation conditions.