Trichoderma harzianum enhances lettuce biomass and modulates plant-soil emerging contaminant dynamics under reclaimed wastewater irrigation

The use of wastewater for irrigation in agricultural soils offers a sustainable means to reduce freshwater consumption and recycle nutrients, but also poses contamination risks associated with emerging pollutants. Furthermore, potentially toxic transformation products may form in soil and rhizosphere, and could subsequently be taken up by plants. Several products containing spores of symbiotic fungi are available and could serve as effective solutions to enhance the biodegradation of micropollutants in agricultural soils irrigated with treated wastewater. In this study, the effect of the fungus Trichoderma harzianum on the distribution of two emerging contaminants, carbamazepine and climbazole, and their main transformation products among soil and lettuce tissues was investigated under controlled conditions. Physiological effects were also investigated by quantifying phytohormones in roots and leaves. Inoculation with Trichoderma harzianum did not significantly affect the uptake of the parent compounds but increased the concentration of their transformation products in soil and reduced their levels in plant leaves after three weeks. The fungus enhanced plant biomass and altered certain phytohormones involved in defense mechanisms such as salicylic acid and microbiome recruitment in roots and soils. Findings of this study provide valuable insights that can be effectively applied to crop cultivation using reclaimed wastewater, leveraging readily available biological products for improved sustainable practices.