Impact of Genetic Background on the Leaf-Protective Enzyme Activity and Hormone Levels of Maize

The delay of leaf senescence, also known as the stay-green (SG) phenotype, is a trait closely associated with yield gain and resistance to many biotic/abiotic stresses. In order to increase the stress tolerance in maize, eight genetic background types were compared against the hallmarks of delayed senescence. The plant redox status and hormonal levels were tested among widespread SG and non-SG (NSG) maize lines in northern China. We found that SG maize lines showed greater activity of the reactive oxygen species (ROS) scavenging apparatus including leaf superoxide dismutases (SOD), peroxidases (POD), and catalases (CAT). Moreover, the concentration of malonaldehyde (MDA), a membrane lipid peroxidation marker, was significantly lower in SG than in NSG plants. For the hormone content, SG maize lines showed higher zeatin (ZR) and lower abscisic acid (ABA) after silking, resulting in a higher ZR/ABA ratio. Understanding the correlation between the stay-green trait and the corresponding hallmarks of delayed senescence is an important step in promoting SG to increase yield and stress tolerance. Our findings provide valuable insight into how to promote the SG trait in specific maize lines to increase yield and stress tolerance.