Evaluation of drought tolerance in late and medium maize hybrids using stress tolerance indices

In order to study the effect of drought stress on grain yield and determining maize hybrids with tolerance to drought stress, a field experiment was conducted in Moghan Agricultural Research field station in 2004 cropping seasons, using a split block arrangement in randomized complete block design with three replications. The experimental Factors were four irrigation regimes as factor A including: (I1: normal irrigation, I2: water stress at vegetative, I3: water stress at flowering and I4: water stress at grain filling stages) and 7 commercial maize hybrids as factor B including: SC704, SC703, SC700, SC720, SC647, SC724,TWC600. Based on grain yield of hybrids in normal and stress conditions, stress susceptibility index (SSI), tolerance (TOL), mean productivity (MP), mean geometric productivity (GMP), stress tolerance index (STI) and Harmonic Mean (MHAR) were calculated. The results showed that, in addition to significant correlation between these indices and grain yield there were also significant relationships between different indices. Since stress tolerance index (STI) was more efficient index in identifying group A from other groups, it was chosen as the most suitable index for selecting tolerant genotypes to drought stress. Therefore, in three-dimension plot only STI index with grain yield in normal and drought stress conditions were used. The plot also identified SC704 and SC647 as tolerant hybrids under drought stress conditions.