Effect of silicon on lignin and sugar concentrations of leaf sheaths in rice plants infected by Rhizoctonia solani

Sheath blight, caused by the fungus Rhizoctonia solani Kuhn, is the major disease affecting rice production worldwide. This study aimed to verify the effect of silicon (Si) on the concentrations of soluble and insoluble lignin and sugars in the leaf sheaths of rice plants infected by R. solani. Rice plants from cultivars BR-Irga-409 and Labelle were grown in nutrient solution without or with Si (2 mM). As compared to plants non-supplied with Si, the Si concentration in leaf sheaths in cultivars BR-Irga-409 and Labelle supplied with Si increased by 77% and 84%, respectively. The relative lesion length of sheath blight was significantly lower in plants supplied with Si compared to non-supplied plants. There was no effect of Si or inoculation with R. solani on the concentrations of mannans, galactans, arabinans, xylans, glucans and sugars in the sheaths of plants from both cultivars. There was no variation in the concentrations of insoluble, soluble and total lignin between the cultivars. The concentrations of total and insoluble lignin were higher on plants supplied with Si regardless of inoculation with R. solani. In conclusion, the rice plants supplied with Si were more resistant to sheath blight due to an increase in the lignifications of the leaf sheath tissues and the lower concentration of total sugars.