Changes of antioxidant enzymes in Fusarium verticillioides- maize pathosystem

Fusarium verticillioides is a fungus of particular importance for its widespread occurrence in cereals, especially in maize. F. verticillioides causes ear and stalk rot of maize, frequently colonizes maize tissue sometimes without causing disease symptoms and produces fumonisins. It is known that an early plant response to pathogen infection is an oxidative burst characterized by a huge production of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and superoxide anion that are potentially toxic for the cells. The ROS level in the cells is under the control of antioxidant defences, such as detoxifying enzymes and low-molecular weight antioxidants. Our aim was to study the trend of some detoxifying enzymes such as superoxide dismutase, peroxidase, catalase and ascorbate peroxidase during the defensive strategy activated by resistant or susceptible plants at five days post treatment with F. verticillioides. Superoxide dismutase and ascorbate peroxidase, the latter considered the key enzyme in cellular H2O2 removal, showed higher activity in resistant than in susceptible caryopses, highlighting their involvement in counteracting the pathogen colonization and mycotoxin accumulation. On the contrary, the decrease of catalase and total peroxidase activity underlined a lower cellular H2O2-detoxifying capacity than other enzymes. This study contributes to better understanding of the molecular and biochemical mechanisms that take part in the activation of the defence responses during biotic stress and that can be useful for fast plant resistance selection programmes