Protective effect of red light against blast disease caused by Magnaporthe oryzae in rice

In this study, the effect of light on the protection of rice against blast caused by Magnaporthe oryzae was investigated. When rice inoculated with M. oryzae was kept in the dark for 24 h and then exposed to various light conditions, the formation of a susceptible blast lesion was significantly inhibited under red light compared with natural or white light. Furthermore, there was greater formation of necrotic spots under red light compared to natural and white lights. The activity of phenylalanine ammonia-lyase (PAL) increased significantly after inoculation with M. oryzae spores in red light-treated rice, as compared with natural or white light-treated rice. This activity reached a maximum at 48 h after inoculation. The amount of cinnamic acid in M. oryzae-infected rice increased significantly after treatment with red light, as compared to treatment with natural light. These results suggested that increased PAL activity and cinnamic acid synthesis were involved in red light-induced resistance to M. oryzae infection. In conclusion, our results indicate that red light triggers the priming of the phenylpropanoid pathway for basal resistance following M. oryzae infection and protects rice plants against blast.

► The role of red light in protecting rice against blast disease caused by Magnaporthe oryzae was investigated.
► Red light triggers an important resistance pathway in rice.
► Phenylalanine ammonia lyase activity and cinnamic acid synthesis are involved in red light-induced resistance.