Inhibitory effect of TiO2 NPs on symbiotic arbuscular mycorrhizal fungi in plant roots.

While nanoparticles (NPs) are known to exhibit antimicrobial properties, their effects on symbiotic arbuscular mycorrhizal fungi (AMF) in plant roots has to be carefully examined as NPs particularly of titanium dioxide (TiO2) reach plant roots through varied sources such as fertilisers, plant protection products and other nanoproducts. The objective of the present study is to assess the effect of TiO2 NPs on the symbiotic behaviour of AMF colonising rice (Oryza sativa L.) plants. Using sol-gel method, TiO2 NPs with three different sizes were successfully synthesised employing doping. Characterisation of the prepared material was done by X-ray powder diffraction and scanning electron microscopy. The synthesised materials were applied at 0, 25, 50 and 100 mg plant-1 to the rhizosphere of mycorrhizal rice plants maintained in pots. The study revealed that the prepared NPs had an inhibitory effect on arbuscular mycorrhizal symbiosis in plant roots. Development of AMF structures such as vesicles and arbuscules was significantly reduced in TiO2-doped NPs with a relatively more inhibition in 2% TiO2-doped NPs. Among the concentrations of TiO2 NPs applied to different treatments, %F was significantly (P < 0.001) affected at medium to higher levels of application.