Evaluation of Water Stress Tolerance of Maize Hybrids using Tolerance Indicies

Maize is one of the most important cereals that is cultivated in many parts of the world and it is one of the most important cereals for the production of food for people all over the world. The most common environmental stress is drought, which limits the growth and survival of plants in arid and semi-arid areas. The selection of tolerant genotypes to drought can help to improve the performance of maize hybrids under these conditions.

In this research, to investigate the tolerance of maize hybrids to drought stress, 18 maize hybrids were evaluated in an experiment in the form of the split-plot design based on a randomized complete block design with three replications. In the control conditions, irrigation was done after 70 mm and under drought stress conditions, after 120 mm of evaporation from the class A pan. Based on the grain yield under water-deficit stress and normal conditions, the indices including the stress tolerance index (STI), stress susceptibility index (SSI), tolerance (TOL), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HARM), reconnaissance drought Index (RDI), drought resistance index (DI), yield stability index (YSI) and selection index of ideal genotype (SIIG) were calculated for the studied hybrids and the most tolerant and sensitive hybrids were identified. Also, the grouping of hybrids was done based on cluster analysis and principal component analysis.

In this research, yield under normal and water-deficit stress conditions had a low correlation with the TOL index, a negative and significant correlation with SSI, and a positive and significant correlation with MP, GMP, STI, HARM, YSI, RDI, DI and SIIG and therefore, hybrids with higher values for these indices had higher yield in the water-deficit stress and normal conditions. Thus, MP, GMP, STI, HARM, YSI, RDI, DI, and SIIG were suitable indices for identifying hybrids with higher yield in both conditions due to their higher correlation with the grain yield in water-deficit stress and non-stress environments.

In normal conditions, SC704, has the highest (18.57 tons/ha) and SC703 (11.81 tons/ha), SC702 (11.76 tons/ha), SC720 (12.66 tons/ha), SC701 (11.77 ton/ha), K19/2×K3651 (11.09) and AR66 (11.43 tons/ha) had the lowest yield. Also, under water stress conditions, SC704 had the highest (15.9 tons/ha) and AR66 had the lowest (6.16 tons/ha) yield. Based on the results of the studied indices, SC500 and SC704 were identified as water deficit tolerant hybrids and SC670 and AR66 were also identified as sensitive hybrids to water deficit stress. The results of cluster analysis and principal component analysis and biplot diagram also confirmed this issue.