Co-Application of TiO2 Nanoparticles and Arbuscular Mycor-rhizal Fungi Improves Essential Oil Quantity and Quality of Sage (Salvia officinalis L.) in Drought Stress Conditions

Drought stress is known as a major yield-limiting factor in crop production that threatens food security worldwide. Arbuscular mycorrhizae fungi (AMF) and titanium dioxide (TiO2) have shown to alleviate the effects of drought stress on plants but information regarding their co-addition to minimize the effects of drought stress on plants is scant. A two-year field experi-ment was conducted in 2019 and 2020 to evaluate the influence of different irrigation regimes and fertilizer sources on the EO quantity and quality of sage (Salvia officinalis L.). The experiment was laid out as split plot arranged in a randomized complete block design with three replicates. The irrigation treatments were 25, 50, and 75% maximum allowable depletion (MAD) percentage of the soil available water as non-stress (MAD25), moderate (MAD50) and severe (MAD75) water stress, respectively. Subplots were four fertilizer sources including no-fertilizer control, TiO2 na-noparticle (100 mg L-1), AMF inoculation, and co-addition of TiO2 and AMF (TiO2 + AMF). Mod-erate and severe drought stress decreased sage dry matter yield (DMY) by 30 and 65%, respec-tively. In contrast, application of TiO2 + AMF increased DMY and water use efficiency (WUE) by 35 and 35% compared to the unfertilized treatment. The highest EO content (1.483%), yield (2.52 g m-2) and cis-thujone (35.84%, main EO constituent of sage) was obtained in MAD50 fertilized with TiO2 + AMF. In addition, the net income index increased by 44, 47 and 76% with application of TiO2 nanoparticles, AMF and co-addition of TiO2 +AMF, respectively. Overall, the integrative application of biofertilizer and nanoparticle (TiO2 + AMF) could be recommended as sustainable strategy for increasing net income and improving EO productivity and quality of sage plants in drought stress conditions. Future policy discussions should focus on incentivizing growers to re-place synthetic fertilizers with proven nano and biofertilizers to reduce environmental footprints and enhance the sustainability of sage production especially in drought conditions.