Integrated Assessment of Drought Tolerance Indices in Maize Genotype Selection

Drought is a major constraint limiting maize productivity worldwide, highlighting the need for reliable methods to identify drought-tolerant genotypes. This study evaluated the effectiveness of drought tolerance indices and multivariate analyses for discriminating maize genotypes differing in drought adaptation. In total, 20 maize genotypes were assessed under optimal and water-limited conditions using grain yield under non-stress (Yp) and drought stress (Ys) together with 15 drought tolerance indices. Correlation analysis, principal component analysis (PCA), clustering, and overlay analysis were applied to identify informative indices and characterize genotype responses. Productivity-oriented indices (STI, GMP, HM, MSTI, REI, and YI) were strongly associated with grain yield and consistently identified superior genotypes, whereas SSI, TOL, and SSPI mainly reflected drought susceptibility. PCA separated productivity and stress susceptibility into two complementary components and showed that five variables (Yp, Ys, YI, ATI, and MSTI_K1) retained 99.49% of the variation explained by the complete dataset. Cluster and overlay analyses confirmed stable genotype classification and distinct adaptation strategies. These findings demonstrate that a reduced set of complementary variables provides an efficient framework for drought tolerance assessment and supports the identification of maize germplasm, combining high productivity with stable performance under variable water availability.