In order to determine the most effective indices for quantifying drought tolerance and identify genotypes
that are tolerant to water stress in bread wheat, 50 bread wheat genotypes were compared in a
randomized complete block design with three replications under both the non-stress dry farming with
two complementary irrigation and the water stress dry farming conditions in Khorramabad, Iran.
Analysis of variance showed that there was a significant difference among the genotypes in terms of all
of the traits except the number of spike per area. In this study, eight indices including: Stress Tolerance
Index (STI), Geometric Mean Productivity (GMP), Mean Productivity (MP), Yield Index (YI),
Harmonic Mean (HM), Yield Stability Index (YSI), Stress Susceptibility Index (SSI), and Tolerance
index (TOL) were calculated by using of seed yield of the genotypes under both conditions. Indices that
selection based on them will improve the yield in both conditions, are considered as suitable index. STI,
GMP, MP and HM were introduced as suitable index for drought resistance selection. Genotypes
Shiroodi and S-90-5 were determined as the most appropriate based on 3D plot. Based on positive
correlation between water stress resistance indices and yield under stress and non-stress environments,
STI and GMP were the best indices. By using the Biplot method, Shiroodi, S-90-5 and Oroum genotypes
were considered as high yielding potential genotypes under the both conditions. According to the results
of cluster analysis, genotypes were classified into three groups based on drought tolerance indices.
Graphical analysis of genotypes also showed that genotypes Shiroodi and S-90-5 were more profitable than
others under both drought stress and non-drought stress conditions. These genotypes could also be used
as parents caring desirable genes in the crossing programs and selection of tolerate genotypes.