The traits affecting wheat grain yield and determining tolerant genotypes using drought indices

The determination of genotypes tolerant to drought stress is of major importance in wheat breeding. A two-year split plot field experiment was conducted to determine the traits affecting wheat grain yield and identify the most tolerant genotypes using drought-tolerant indices. Drought stress was applied to 28 genotypes by stoppage of irrigation at the growth stage of 50% inflorescence emergence. Crop yield and growth components were determined. Drought tolerance indices, correlation coefficients, multiple regression as well as path and cluster analyses were applied to determine the most tolerant genotypes. Analysis of variance indicated significant differences among genotypes in terms of growth and yield. The genotype by treatment interaction was also significant. Drought tolerance indices indicated that Darya, Aftab, URBWYT-94-2 and URBWYT-94-4 were the most tolerant genotypes. URBWYT-94-2 had the highest average grain yield under drought stress. Correlation coefficients indicated a significant and positive correlation between geometric mean productivity (GMP) and mean productivity (MP) indices as well as between stress susceptibility (SSI) and drought tolerance (TOL) indices (p <= 0.01). Stress tolerance index (STI) was significantly correlated with MP and GMP. A significant correlation was found between harmonic (HARM), STI, GMP and MP indices (p <= 0.01). STI and GMP were the most suitable indices to identify drought-tolerant wheat. According to path analyses, the correlations among wheat yield components were positive and significant.