Activities of antioxidant enzymes in three species of Ludwigia weeds on feeding by Altica cyanea

Abstract

ObjectivesAltica cyanea (Weber) (Coleoptera: Chrysomelidae) is a potential biocontrol agent of rice-field weeds, Ludwigia adscendens (L.) Hara, L. parviflora Roxb., and L. octovalvis (Jacq.) Raven (Onagraceae) in India. Damage on leaf tissue causes stress on plants. Hence, this study aims to observe how the three Ludwigia species are trying to cope with the stress caused by feeding of A. cyanea adults at different time intervals. MaterialsUninfested L. adscendens, L. parviflora, and L. octovalvis, and each Ludwigia species on which 5 adult A. cyanea females had fed on continuously for 6 h or 48 h were used for collection of leaf tissues. The amounts of total ROS, H2O2, activity of enzymatic antioxidants [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), activity of peroxidases towards phenolic substances {guaiacol peroxidase (GPX) and pyrogallol peroxidase (PPX)}, and ascorbate peroxidase (APOX)] and non-enzymatic antioxidants (phenolics and thiols) were estimated from leaf tissues of undamaged and insect damaged Ludwigia species using standard protocols. ResultsThe amounts of total ROS and H2O2 were higher in each Ludwigia species after 48 h feeding by A. cyanea followed by plants after 6 h feeding by A. cyanea and undamaged plants. The activities of antioxidant enzymes such as CAT, SOD, GST, APOX, PPX, and GPX were higher in each Ludwigia species after 48 h feeding by A. cyanea compared to undamaged plants. Total proteins and thiols were higher in each undamaged Ludwigia species compared to insect damaged plants; whereas total phenols were higher in each insect damaged Ludwigia species compared to undamaged plants. ConclusionsHigher amounts of total ROS and H2O2 in each insect damaged Ludwigia species compared to undamaged plants suggested that A. cyanea feeding resulted stress in the insect damaged plants. Higher amounts of CAT, SOD, GST, and APOX in insect damaged Ludwigia species compared to undamaged plants suggested that these four enzymes were acting as antioxidants to reduce the stress created in plants due to insect herbivory.