Wheat Genotype S615 Carrying the <i>Rmg8</i> Gene Exhibits Enhanced Antioxidant Defense for Resistance to <i>Magnaporthe oryzae Triticum</i>

Wheat blast caused by the fungus <i>Magnaporthe oryzae Triticum</i> (MoT) pathotype is a catastrophic disease that threatens global food security. Recently, <i>Rmg8</i> was discovered as a blast resistance gene in wheat genotype S615. However, although <i>Rmg8</i> has recently been cloned, the precise underlying biochemical and molecular mechanisms by which this gene confers resistance against MoT remain to be fully elucidated. This study investigated the antioxidant defense mechanisms in the wheat genotype S615, which carries the blast resistance gene <i>Rmg8</i> against MoT infection, compared with the blast-susceptible wheat variety BARI Gom-26 (BG26). Artificial inoculation of wheat heads with MoT followed by biochemical analyses revealed that the levels of hydrogen peroxide (H₂O₂), lipoxygenases (LOXs), and malondialdehyde (MDA) in rachis tissues increased significantly until 48 h after inoculation in both S615 and BG26. However, LOX and MDA concentrations were substantially lower in S615 than in BG26. These biochemical alterations may have contributed to less damage to photosynthetic pigments, such as chlorophyll <i>a</i>, chlorophyll <i>b</i>, total chlorophyll, and carotenoids in the rachis of S615. The S615 genotype exhibited significantly higher levels of several enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase) and non-enzymatic (e.g., proline) antioxidants in the MoT-inoculated rachis tissues than in those of BG26. To the best of our knowledge, this study biochemically demonstrates for the first time that the blast resistance in S615 is, in part, correlated with its strong antioxidant defense responses to MoT infection, providing a physiological basis for this resistance mechanism.