Exogenous Methyl Jasmonate Treatment Induces Defense Response Against Fusarium culmorum in Wheat Seedlings

Abstract

The Fusarium crown and root rot (FCRR) pathogen Fusarium culmorum (Fc) is a hemibiotrophic pathogen, with a short biotrophic phase preceding necrotropism. Methyl jasmonate (MeJA) has been identified as a vital growth regulator, and in the current study MeJA (200 μM) was applied at 2 days post Fc-inoculation (2 dpi) to compare wheat responses to F. culmorum challenge with responses induced by treatment with the plant defense signaling molecule during the necrotrophic stage. Our results show that a chemically induced protection significantly reduced necrotic symptoms in wheat cultivars over a 3 week period after inoculation. The activities of defense enzymes consisting of SOD, CAT, POX, PPO, LOX and PAL as well as total phenols and callose content, were enhanced earlier and to higher levels in tolerant cv Sumai3. In contrast to pathogen infection, there was not a general trend of an enhancement in cv Sumai3 following chemical treatment. In addition, MeJA significantly decreased the level of H2O2 contents and lipid peroxidation in all wheat cultivars studied. These results suggest that inducing JA dependent defense signaling after pathogen challenge may increase the resistance to FCRR by stimulating enzymatic activities and accumulation of phenolic compounds. This study apparently provides the first evidence of physiological and biochemical responses in wheat following MeJA treatment during the necrotrophic stage of infection. Based on the results, it can be concluded that there was a positive correlation between the wheat resistance levels and time of chemical treatment.