EFFECT OF ZINC OXIDE NANOPARTICLES ON BROWN SPOT DISEASE AND RICE PRODUCTIVITY UNDER SALINE SOIL

The present study investigates the effect of zinc oxide nanoparticles (ZnO-NPs) on rice plants growth and their role in management of brown spot disease caused by the causal agent Helmenthosporium oryza. The antifungal activity of ZnO-NPs (20 to 35 nm particle size) was evaluated at different concentrations. Spores germination percentage, colony formation and sporulation of H. oryza were reduced at concentrations 25 and 50 ppm, in vitro. The greenhouse results showed that seed soaking treatment and foliar spray 5 day before inoculation (DBI) of ZnO-NPs leaded to reduce infection percentage of brown spot without significant difference between ZnO-NPs concentrations. Foliar spray 2 days post-inoculation (DPI) with the lower concentrations 10 and 25 ppm of ZnO-NPs were able to reduce infection percentage of brown spot. Under field conditions, During 2013 and 2014 seasons at El-sirw Agriculture Research Station, Dammietta, Egypt, rice varieties Giza 177, Giza 178 and Giza 179 under ZnO-NPs level (0, 10, 20 and 30 ppm) as foliar spray twice at mid tillering and panicle initiation stages were evaluated. Application of ZnO-NPs at level 20 ppm effectively reduced brown spot disease severity and discolored grains of all tested varieties. The studied rice varieties were varied in their growth, yield attributes, grain yield and brown spot severity whereas Giza 178 and Giza 179 had good performance under ZnO-NPs treatments. Therefore both Giza 178 and Giza 179 had showed significant salt tolerance at 20 ppm of ZnO-NPs. The performance of Giza 177 as a salinity-sensitive variety was improved at 20 ppm ZnO-NPs. The all ZnO-NPs treatment positively improved rice growth, yield attributes, rice grain yield and brown spot severity over control treatment. Finally, ZnO-NPs can be used as future “nanofertilizers”.