Screening Wheat Landrace Varieties for Grain Yield under Water Deficit Conditions Using Drought Tolerance Indices

In order to evaluate the performance of wheat (Triticum aestivum L.) genotypes under drought stress at heading stage, 100 Iranian landraces and two commercial cultivars were grown under well- watered irrigation and a drought stress treatment as 50% field capacity (FC) irrigation that started at heading stage in 2010-2011 growing season. Results showed that spike length (SL), grain number/spike (GN), thousand kernel weight (TKW)and grain yield (GY) were reduced by 8.2%, 14.6%, 17.5% and 52.5% due to drought stress at heading stage. GN had highest heritability (88%) compared to other grain yield related traits. The range for SL varied from 4.6 to 15.0 cm and some of landraces had higher SL than commercial varieties. KC4880 had the highest GN (40.6) in drought stress condition and it was in the second rank (42.3) after KC3885 (44.6) under well-watered treatment. The mean values for grain yield per square meter in well-watered plots varied from 586.1 to 811.1 g, while under drought stress conditions the range was from 217.0 to 546.3 g. The highest TKW (44.33 g) was observed in KC4502 in well-watered treatment while the lowest (23.08 g) belonged to the genotype KC4700. There were significantly positive correlations between grain yield under well-watered conditions (YP) and the indices tolerance (TOL) (r= 0.71), mean productivity (MP) (r= 0.31) and stress susceptibility index (SSI) (r= 0.55). Principal component analysis (PCA) indicated that MP, geometric mean productivity (GMP) and stress tolerance index (STI) were more appropriate for prediction of Ys and based on biplot of two PCs genotypes were classified. Based on the positive correlation between stress tolerance index (STI) (r= 0.90) or geometric mean productivity (GMP) (r= 0.92) and grain yield, it can be concluded that the landraces such as KC4907, KC4863, KC4144, KC4779, KC4641, KC4880, KC4494, KC4502, with the highest GMP (ranged from 578.8 to 636.4) and STI (0.85-0.65) can be considered as drought tolerant in wheat breeding programs.