Wheat Genotype S615 Carrying the Rmg8 Gene Exhibits Enhanced Antioxidant Defense for Resistance to Magnaporthe oryzae Triticum.

Abstract

Wheat blast caused by the fungus Magnaporthe oryzae Triticum (MoT) pathotype is a catastrophic disease that threatens global food security. Lately, Rmg8 was discovered as a blast resistance gene in wheat genotype S615. However, while Rmg8 has recently been cloned, the precise underlying biochemical and molecular mechanism by which this gene confers resistance against MoT, remains to be fully elucidated. This study investigated the antioxidant defense mechanisms in the wheat genotype S615, which carries the blast resistance gene Rmg8 against MoT infection, compared to 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 (LOX), and malondialdehyde (MDA) in rachis tissues increased significantly until 48 hours after inoculation in both S615 and BG26. However, LOX and MDA concentrations were substantially lower in S615 than BG26. These biochemical alterations may have contributed to less damage to photosynthetic pigments such as chlorophyll a, chlorophyll b, total chlorophyll (Tchl), and carotenoids in the rachis of S615. The S615 genotype exhibited significantly higher levels of several enzymatic (SOD, CAT, APX, GPX, GR, DHAR, and MDHAR) 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.