Study of selection indices for drought tolerance in some of grain maize hybrids

To study the drought tolerance in some of grain maize hybrids, this study was carried out in Qom province in 2006 cropping season. Twenty maize hybrids were evaluated in randomized compelet block design with four replications, in two separate expriments, under normal irrigation(30% depletion of available water) and drought stress (60% depletion of available water). Results of analysis of variance for grain yield and its components showed variation among hybrids under normal and drought stress conditions. The highest yield under normal and stress conditions belonged to hybrids BC504 and BC652, repectively. While, hybrids BC678 and NS504 showed the lowest yield under normal and stress conditions, respectively. To evaluating the response of hybrids to drought stress, different indices, including, Stress Susceptility Indices (SSI), Harmonic mean (Harm), Tolerance index (TOL), Mean Producivity (MP), Stress Tolerance Index (STI) and Geometric Mean Productivity (GMP) were used. Different indices revealed hybrids BC504, BC652, BC404, KSC302, KSC320 and KSC647 as tolerance under stress condition. STI, MP, GMP and Harm indices, were identified as suitable indices to be used in applied maize breeding programs. These indices showed the highest corrolation between grain yield under normal and drought stress conditions.