Influences of silicon on activities of pathogenesis-related proteins and contents of total soluble phenolics and lignin in rice leaves infected by Magnaporthe grisea and its relation to induced rice blast resistance

A series of hydroponics experiments were performed in controlled rice- Magnaporthe grisea pathosystem to study the effects of silicon (Si) on activities of chitinase and β-1,3-glucanase and contents of phenolics and lignin. Regardless of silicon amendment, exochitinase and endochitinase activities had entirely consistent trend, and both rapidly increased after inoculation. Chitinase activity in Si-plants reached the first peak at 2 d after inoculation, and thereafter began to decline. However, chitinase activity in Si+ plants continuously increased until 4 d after inoculation and was significantly higher than in Si- plants from 4 d to 8 d. By contrast, silicon application decreased β-1, 3-glucanase activity in rice leaves infected by M. grisea. Contents of total soluble phenolics and lignin in Si+ plants were significantly higher than in Si- plants. However, lignin content in Si+ plants was significantly lower than in Si- plants at 6 d after inoculation. These findings support the hypothesis that silicon is closely involved in induced resistance to rice blast.