Abstract
In order to genetic investigation of drought resistance indices, on 25 maize inbred lines, an experiment was conducted under three irrigation regimes; normal irrigation, limited vegetative irrigation and limited reproductive irrigation. In the limited vegetative irrigation, TOL (Stress Tolerance) index had the highest phenotypic and genotypic coefficient of variation (83.83% and 68.04% respectively) and SSI (Stress Susceptibility Index) had highest phenotypic and genotypic coefficient of variation (79.59% and 60.19% respectively). The MP (Mean productivity), GMP (Geometric Mean Productivity) and STI indices had highest phenotypic and genotypic correlation with grain yield under limited irrigation and had significance correlation with grain yield, kernel per row, row per ear and 500- grain weight under normal irrigation condition. The results of limited reproductive irrigation also indicated that GMP had highest phenotypic and genotypic coefficient of variation. MP, GMP, STI and SSI (Stress Susceptibility Index) indices showed significant phenotypic and genotypic correlation with grain yield, kernel per row, row per ear and 500- grain weight traits under limited irrigation in reproductive condition. MP, GMP, STI and SSI indices had significant phenotypic and genotypic correlation with grain yield, kernel per row, row per ear and 500- grain weight traits under normal irrigation condition. With consideration of phenotypic and genotypic coefficient of correlation, drought indices that had high correlation with studied traits can be used to improve them.

Key words: Maize, Tolerance index, Drought, correlation, Vegetative stress, Reproductive stress