Seed coating with a Serendipita indica–ZnO/Ag nanobiocomposite enhances growth and yield-related traits of rice (Oryza sativa L.)

Rice ( Oryza sativa L.) productivity is constrained by nutrient deficiency and environmental stress, and nanotechnology-based delivery systems offer new options for crop improvement. Here we developed a nanobiocomposite (NBC) by growing the root endophyte Serendipita indica with biosynthesized ZnO (700 ppm) and Ag (100 ppm) nanoparticles (NPs) and applied it to rice as a seed coating. The NPs, synthesized with Azadirachta indica and Aloe vera extracts, had hydrodynamic diameters of 23.3 nm (ZnO) and 65.4 nm (Ag). Growth with the NPs increased fungal dry cell weight by 96.9% and radial growth by 27.8% relative to the control. In a pot experiment, NBC-treated seedlings had the longest shoots (31.8 vs. 11.1 cm in the control) and the highest root length and dry weights after 30 days. In a four-month field trial, NBC-treated plants at harvest were taller (126.0 vs. 98.0 cm), had greater shoot dry weight (49.9 vs. 33.0 g), longer panicles (35.2 vs. 24.0 cm), heavier grains (1000-grain weight 28.7 vs. 24.1 g) and higher chlorophyll and total carbohydrate contents than untreated plants (all P < 0.05). Roots of NBC-treated plants were colonized by the fungus. NBC seed coating is therefore a promising approach for improving rice growth and yield-related traits.