Similar yield of modern maize hybrids under drought is provided by different physiological and metabolic mechanisms.

Abstract

Drought severely limits crop productivity, and the processes that support yield stability in modern maize heterotic hybrids remain insufficiently characterized. We evaluated two maize elite F1 hybrids, H.393 and H.166, under prolonged moderate water deficit in greenhouse and field conditions to identify genotype-specific mechanisms of drought resistance. These two hybrids previously selected in the Steppe zone of Ukraine, yielded 5.75-8.57 t/ha in droughts of 2022-2024, with no significant yield differences between the hybrids. Water stress reduced plant height, contents of chlorophylls, carotenoids, and several minerals in both hybrids demonstrated contrast adaptive strategies to drought. H.393 exhibited a metabolic response, including strong maintenance of leaf water status, activation of guaiacol peroxidase, and distinct shifts in Na and Mg homeostasis revealing drought-avoidance strategy with metabolic adjustment. In contrast, H.166 preserved stable PSII activity, sustained photochemical performance, high PIABS values, great proline accumulation, and elevated concentrations of Mn, Cu, and Zn in leaves manifested adaptive drought-tolerance strategy. Three-factor ANOVA confirmed significant contributions of genotype, water regime and stress duration to the development of most traits, revealing divergent physiological trajectories underlying similar agronomic outcomes. These findings demonstrate that comparable yield stability can arise from fundamentally different mechanisms of drought resistance and highlight the importance of integrating physiological, biochemical, and photochemical markers into breeding programs. Such insight supports more targeted maize improvement and the development of maize hybrids with predictable resilience to increasingly variable climatic conditions.