BIOGENIC SILICA NANOPARTICLES, SYNTHESIS, CHARACTERIZATION AND ANTIFUNGAL ACTIVITY AGAINST TWO RICE PATHOGENIC FUNGI

silica nanoparticles (Si NPs) were extracted by different methods from mrice husk (RH)and ric estraw (RS), and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For the XRD results, the crystalline size was calculated using Scherer equation. The particle size of rice husk nanoparticles (RHNPs) and rice straw nanoparticles (RSNPs) were 73.6 nm and 133.7 nm, respectively. Silica present in RHNPs and RSNPs was about 22.78 and 9.56%, respectively. Si NPs were effective in controlling rice blast (Pyricularia grisea) and brown spot (Bipolaris oryzae) fungal diseases under greenhouse conditions during 2015 season. Efficiency of soil application with RHNPs and white rice husk ash WRHA 92.56 & 90.90% at the rate of 1.5 g/1kg, were the most effective treatments to reduce blast disease severity compared to other treatments as well as control. On the other hand, rice plantswere treated with liquid potassium silicate (K2SiO2), WRHA and RHNPs gave 96.92, 93.07 and 91.53 % efficiency, respectively as foliar application for the control of brown spot disease compared with other treatments. SEM/energy-dispersive spectrometer (EDX) observations and X-ray spectra of adaxial surfaces of the fourth rice leaves Sakha 101 rice cultivar) in soil applied with 1.5g/1kg gave different types of silicified cells. The corresponding EDX spectra compared with the SEM images demonstrated differences in silicon content between soil treated by RHNPs 13.75% and nontreated plants 10.6%. Silicon accumulation in Sakha 101 rice leaves treated with RHNPs as soil application at 1.5g/1kg was increasing Si layers in epidermal cell walls, cuticle and the thickness of the silicon layer. Also, outer regions of epidermal cell walls and intercellular spaces within sub-epidermal tissues. All the silicon layers may be playinga role in increasing the resistanceof rice plants and controlling the rice diseases.