Evaluation of grain yield indices in hexaploid wheat genotypes in response to drought stress

Drought stress limits crop production in the world. Therefore, employing high-yielding cultivars tolerant to drought is an effective approach to reduce its detrimental effects. To identify drought-tolerant genotypes, 36 wheat genotypes were evaluated during the 2010–2011 and 2011–2012 growth seasons. A field experiment was conducted in a split-plot design with two irrigation treatments (100% field capacity (FC) until harvest and no irrigation after anthesis) as main plots in three replications and genotypes as subplots. Grain yield, its components and drought tolerance indices were measured. Results showed a significant reduction in yield and its components under drought conditions. Grain yield had significant positive correlations with stress tolerance index (STI), mean productivity (MP) index and geometric mean productivity (GMP), while it was negatively correlated with stress susceptibility index (SSI) and tolerance index (TOL) under stress condition. These results indicated that superior genotypes could be selected based on high values of STI, MP and GMP and low value of SSI. The results were validated by principal component analysis (PCA) as it showed genotypes with high PC1 and low PC2 were more desirable. Based on the results, genotypes number 8, 11, 17, 30, 34 and 35 were recognized as suitable for both conditions.