Low temperature elicits differential biochemical and antioxidant responses in maize (Zea mays) genotypes with different susceptibility to low temperature stress

Maize, a C4 sub-tropical crop, possesses higher temperature optima as compared to the C3 plants. Low temperature (LT) stress confines the growth and productivity of maize. In this context, two maize genotypes, LT tolerant Gurez local and LT susceptible Gujarat-Maize-6 (G-M-6) were analysed in present study for various osmolytes and gene expression of antioxidant enzymes including Ascorbate–glutathione (AsA-GSH) besides trehalose biosynthetic pathways. With the progressive LT treatment, Gurez local showed lesser accumulation of stress markers like hydrogen peroxide (H2O2) and malondialdehyde, a significant increase in osmoprotectants like free proline, total protein, total soluble sugars, trehalose, total phenolics and glycine betaine, and a significant reduction in the plant pigments as compared to the G-M-6. Additionally, Gurez local was found to possess a well-established antioxidant defense system as revealed from the elevated transcripts and enzyme activities of various enzymes of AsA-GSH pathway. Higher gene expression and enzyme activities were exhibited by superoxide dismutase, catalase and peroxidase besides the gene expression of trehalose biosynthetic pathway enzymes. Moreover, through principal component analyses, a positive correlation of all analysed parameters with the LT tolerance was noticed in Gurez local alone demarcating the genotypes on the basis of their extent of LT tolerance. Overall, the present study forms the basis for unravelling of LT tolerance mechanisms and improvement in the performance of the temperate maize.