The study of physiological responses of different wheat varieties to water stress could be a useful tool to understanding of the mechanisms of drought resistance. This field study was conducted to evaluate the effect of water deficit stress on proline accumulation rate and wheat grain yield at Iran in 2008. A bread wheat (line N84-12) was evaluated by contrasting irrigation regimes (well-watered) (control condition), water deficit stress before tillering stage (T1) and after heading stage (T2). The experiment was carried out using a randomized complete block design (RCBD) with three replications. To impose water deficit stress, plants wasn't irrigated before T1 and after heading T2. The analysis of variance showed that water deficit stress significantly affected grain yield, straw yield, proline accumulation rate and harvest index (HI) in P?0.01. The highest proline accumulation rate was observed under T2 condition and grain yield was decreased by water deficit stress compared with control condition.
