Abstract: 【Objective】 Rice blast is one of the major diseases in rice production and cause serious yield losses every year. As a kind of environment friendly disease control measures, silicon fertilizer application plays an important role in enhancing plant disease resistance, but the mechanism is not totally clear. The purpose of this study was to investigate the physiological mechanism of silicon-enhanced resistance of rice to blast，and to provide a theoretical foundation and methods of controlling rice blast. 【Method】 Two rice near-isogenic lines(NILs) with different resistances to blast, i.e. CO39 (susceptible) and C101LAC (Pi-1) (resistant) were used in the experiments. There were four treatments: no silicon added and no inoculation with M. oryzae(Si-M-); silicon added but no inoculation with M. oryzae(Si+M-); no silicon added but inoculation with M. oryzae(Si-M+); silicon added and inoculation with M. oryzae(Si+M+). Using a grown chamber to control the growing conditions, the hydroponic culture experiments with Hoagland’s nutrient solution were conducted to clarify the effects of silicon on disease incidence, content of silicon, phenolics, SA, ethylene and H2O2 in roots and leaves of rice. 【Result】 Si application significantly reduced the blast incidence and disease index for both two rice lines. And the blast incidence and disease index of C101LAC (Pi-1) were obviously lower than CO39. Si concentration increased significantly in all leaf, stem and root tissues of both two rice lines by Si treatment regardless of inoculation. While Si concentrations in leaves and stems were obviously higher than that in roots. After inoculation with M. oryzae, Si treatment significantly reduced the total phenolic content in leaves of CO39 and C101LAC (Pi-1). In roots of two rice lines, Si application had no significant effect on the total phenolic content. Without inoculation, Si application had no significant impact on the total phenol content in leaves 3 d after inoculation, but reduced it 7 d after inoculation for both rice lines. The content of total phenol was obviously lower in roots than in leaves. After inoculation with M. oryzae, Si treatment significantly reduced the lignin content in leaves of CO39 and C101LAC (Pi-1), but there were no significant effect in roots. Without inoculation, Si application significantly increaced SA content in leaves 3 d and 7 d after inoculation for CO39, but only 7 d after inoculation for C101LAC (Pi-1). Si application also significantly increased SA content in leaves of CO39 3 d after inoculation, but not in C101LAC (Pi-1). SA was not detected in roots for both CO39 and C101LAC (Pi-1). Under the condition of inoculation, Si supply significantly reduced ethylene content in leaves and roots for both CO39 and C101LAC (Pi-1). Without inoculation, Si application significantly reduced ethylene content in roots on 3 d after inoculation for CO39, and 3 d and 7 d for C101LAC (Pi-1). After inoculation with M. oryzae, Si treatment significantly reduced the H2O2 content in leaves, but significantly increased it in roots, for both CO39 and C101LAC (Pi-1). H2O2 content was obviously lower in roots than in leaves for both rice lines. 【Conclusion】 These results indicate that Si can significantly increase the blast resistance of rice. Si addition can adjust biochemical metabolism of phenolic compounds in plants, and leads to variation of the signal compounds such as SA, ethylene, H2O2 in the rice to enhance the resistance against blast.

Key words: rice (Oryza sativa L.) , Magnaporthe oryzae , silicon , root system , phenolic compounds , ethylene