Biogenic silica: A promoter of cell wall strengthening and induced resistance against sheath blight disease in rice via salicylic acid signaling and phenolic metabolism

Sheath blight disease has recently spread in Egypt; particularly, there are no sources of cultivar resistance to the disease worldwide, so silicon has a vital role as part of the management of sheath blight disease in rice. The aim of the study is to use different sources of silica as compared to fungicides to control sheath blight on rice. In addition, resistance mechanisms between the host and pathogen after treating the host with silica were inves-tigated. The results of study show white rice husk ash (WRHA) application was more effective in stopping the development of rice sheath blight disease, had less dense mycelium growths, increasing silica cell content, and there are more guard cells around the stoma on the leaves' surface. The epidermal cell walls of treated plants with WRHA were generally thicker than those of uninoculated ones. Electron-dense silicon layers were easily discernible in the epidermal cell walls of silicon-treated plants. Ultra-structural changes in the chloroplast were observed and revealed that treated leaves with WRHA were full and clear. Silica incorporated into the soil and sprayed on rice plants at the vegetative growth stages played a significant role in inducing rice resistance to sheath blight disease. Gene expression analysis demonstrated an accumulation of salicylic acid (SA)-linked transcriptions on diverse sources of silica treatment. Two days following the inoculation, these genes, OsNPR1 and OsWRKY45, recorded 14.45 and 11.52-fold changes, respectively, with rice treated by WRHA. Phenolic metabolisms were increased in rice plants treated with WRHA and inoculated with Rhizoctonia pathogen.