PJB-2022-413
ROS MANAGEMENT AND PSII ACTIVITY ARE KEY PHYSIOLOGICAL DETERMINANTS FOR RESISTANCE AGAINST MECHANICAL WOUNDING AND SPODOPTERA FRUGIPERDA INFESTATION IN MAIZE (ZEA MAYS L.)
Fozia Saeed
Abstract
Abstract
Wounding and herbivory are serious threats for plant growth and crop productivity, because both these stresses damage the quality and quantity of photosynthetic tissues. Thus, it was aimed to assess whether or not growth reduction due to mechanical injury and/or insect herbivory by fall armyworm was associated with changes in photosynthesis and antioxidant potential in resistant and susceptible maize inbred lines. For this purpose, five-week-old maize plants were subjected to mechanical wounding and Spodoptera frugiperda feeding for 48 hours. Data revealed that all maize lines differed in their resistance mechanism, V121 was found susceptible genotype and V108 and V122 were found resistant genotypes. Our results showed that insect herbivory, mechanical wound and combination of these treatments significantly decresed shoot fresh and dry biomass, chlorophyll contents and quantum yield of PSII (Fv/Fm) in all maize inbred lines. However, insect herbivory had maximal adverse effect on plant growth, photosynthetic pigment and quantum yield of PSII. Wounding or insect herbivory caused the generation of reactive oxygen species (ROS, measured as H2O2) that resulted in membrane damage (measured as MDA). In addition, both maize genotypes increased the activities of battery of antioxidant enzymes (CAT, POD and SOD) to counteract ROS. The resistant genotypes V108 and V122 had greater antioxidant potential. In addition, accumulation of non-enzymatic antioxidant compounds such as phenolics and flavonoids, and osmoprotectants such as proline were also higher in resistant genotypes V108, and V122. Wounding and insect herbivory reduced the quantum efficiency of PSII with increase in non-photochemical quenching (NPQ). However, reduction quantum yield of PSI due to wounding and/or insect herbivory was associated with donor end limitation of PSI [Y(ND)]. In addition, resistant genotype had lesser Y(ND), which indicated wounding or insect herbivory did not affect physiological processes downstream to PSI. Thus, the present study highlighted that maize genotypes V108 and V122 were resistant to mechanical wounding and Spodoptera frugiperda infestation, which was associated with better management strategy for ROS and membrane damage by activating antioxidant enzymes and accumulation of osmo-protectants that resulted in better PSII activity.
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