Biochemical Characterization of Parental Inbred Lines and Hybrids of Maize (Zea mays L.) under Different Irrigation Conditions

Maize (Zea mays L.) is a significant crop with extensive agricultural and economic importance worldwide. With increasing concerns over water scarcity and climate change, understanding the responses of maize plants under water stress conditions is crucial to develop drought-tolerant cultivar (s). In present investigation, alteration in different biochemical parameters, including chlorophyll content, malondialdehyde (MDA) levels, hydrogen peroxide (H2O2) content, peroxidase, glutathione reductase (GR), and catalase activities, among 12 parental inbred lines along with 66 hybrids and two checks under irrigated and partial irrigated conditions were examined. Under irrigated conditions, the chlorophyll content was highest in the parental inbred line IL8, intimately followed by IL6, while IL5 exhibited the lowest content. MDA levels were significantly higher in the parental line IL8 and hybrid IL1 × IL6, whereas IL5 and IL3 × IL11 exhibited the lowest levels. H2O2 content was found to be highest in the parental line IL5 and hybrid IL8 × IL12, whereas IL4 and IL2 × IL5 displaying the lowest levels. Peroxidase activity was highest in IL7 and hybrid IL1 × IL7, whilst IL6 and IL4 × IL7 showed the lowest activity. Glutathione reductase activity was found highest in IL1 and IL9 × IL12, whereas IL6 and hybrid IL1 × IL3 exhibited the lowest activity. Catalase activity was highest in IL8 and IL2 × IL10, while IL4 and IL2 × IL6 displayed the lowest activity under irrigated conditions. Under partial irrigated conditions, almost similar trends were documented for the most of parameters, with slight variations in the expression levels. Notably, the drought-tolerant genotypes demonstrated higher chlorophyll content, peroxidase, glutathione reductase, and catalase activities, while drought-sensitive genotypes unveiled elevated MDA levels and H2O2 content. Phylogenetic analysis revealed five major clusters, indicating significant variability in different biochemical profiles among the genotypes. The heat map analysis supported the identification of distinct expression patterns of biochemical parameters, contributing to our understanding of the genotypic responses to varying irrigation conditions. These findings provide valuable insights for maize breeding programmes aimed to breed drought-tolerant cultivar (s) with enhanced antioxidant defences and stress tolerance.