Application of jasmonic acid at the stage of visible brown necrotic spots in Magnaporthe oryzae infection as a novel and environment-friendly control strategy for rice blast disease.

Rice blast disease is one of the most common rice diseases worldwide. It is essential to improve disease resistance through environment-friendly methods, while maintaining yield and quality parameters. In this study, jasmonic acid (JA), a plant hormone with anti-fungal activity, was obtained, at both low (100 μmol/L) and high (400 μmol/L) concentrations in rice leaves, before, during, and after infection, respectively. JA could inhibit germination and appressorium formation of rice blast spores in a dose-dependent manner. A total of 400-μmol/L JA treatment significantly enhanced cell viability and endogenous JA level in rice leaves. Furthermore, rice leaves inoculated with Magnaporthe oryzae and sprayed with JA 72 h post-inoculation showed the maximum symptom relief and the highest endogenous JA production among all treatment approaches. The expressions of defense-related genes, OsPR10a and OsAOS2, were highly up-regulated in response to JA, whereas OsEDS1 was down-regulated. Hence, we revealed that exogenous JA could activate JA signaling to effectively control the symptoms of rice blast.