Evaluating Tolerance Indices of some New Maize Hybrids Imposed to Drought Stress

In order to investigate drought tolerance indices of 14 maize hybrids to different levels of water deficit, a split-plot experiment was conducted in complete randomized block design with four replications at the Agricultural Research Station, University of Tabriz. The main plots consisted of three levels of irrigation regimes (control, mild and severe water deficit) and sub-plots of 14 corn hybrids. Drought tolerance indices were calculated for the grain yields produced. Under mild drought condition, hybrids like SC702, SC500 and K3647×K18 were tolerant based on tolerance index (TOL) and stress susceptibility index (SSI) indices while hybrid SC 500 was the most tolerance one. Based on stress tolerance index (STI), mean productivity (MP) and geometric mean productivity (GMP) indices under both mild and severe stress conditions hybrids K166×K18, SC500¡ K3647×K18 and SC400 were found to be the most tolerant to water deficit than others. The STI and GMP indices that had highest positive correlation with grain yield under both of these stress conditions. Thus these two indices were determined as the best indices for selection of tolerant hybrids. Cluster analysis based on these two indices classified hybrids into two groups under mild stress and in three groups under severe stress conditions. Biplot graphs for two main components based on principle components analysis (PCM) displayed that SC500 to be a tolerant maize hybrid in both mild and severe drought stress conditions with high yield performance. Also, hybrids SC700 and SC704 were low yielders under both control and stress conditions and thus were identified to be as sensitive hybrids.