Abstract

The purpose of this study was to evaluate the effect of drought stress on wheat yield and yield components. A large number of studies were conducted regarding damage to crops due to drought over the world. Since there is a considerable amount of field studies, the use of these data can provide an overall view of the factors and variables affecting crop attributes by meta-analysis methodology. To do this, after reviewing the articles, traits and treatments that had the most frequency in the articles including grain yield, harvest index and 1000-grain weight were selected. According to the information obtained, grain yield, harvest index and 1000-grain weight in most articles were placed on the left of forest diagram, highlighting a decrease in the average of each trait under drought stress. In these studies, the standardized mean difference (SMD) between treatments was 0-(−4.10) for grain yield, 0-(−1.78) for harvest index and 0-(−2.95) for 1000-grain weight. It can be said that the effect size of changes in stress treatment compared to control was low to moderate and the per cent changes for the above-mentioned traits were 32, 15 and 20%, respectively. The effect size indicators were used to evaluate the differences between treatments in different studies. Cohen indicator changes between traits were in the range of 1.9248–4.4280. The maximum and minimum Cohen indicator changes were found for grain yield and harvest index, respectively. Low amounts of Cohen indicator for harvest index indicated less change in this trait under drought stress and its stability.