Utilization of Municipal Biowaste-Derived Compounds to Reduce Soilborne Fungal Diseases of Tomato: A Further Step Toward Circular Bioeconomy

A crucial point for the ecological transition toward a circular bioeconomy is represented by the utilization of municipal biowaste for novel uses in agriculture. Thus, in vitro and in vivo performance of oxidized biopolymers (Ox BPs) obtained from the organic fraction of municipal waste was evaluated against Rhizoctonia root rot and southern blight of tomato (Solanum lycopersicum L.). Further, the selectivity of these biopolymers was evaluated on young tomato seedlings. Effects of Ox BPs were tested at 100, 1000, and 5000 μg mL⁻¹ in reducing Rhizoctonia solani and Sclerotium rolfsii mycelial growth and decreasing relative infections in tomato. The effective concentrations able to reduce mycelial growth by 50% and 95% (EC₅₀ and EC₉₅) calculated according to logit models and minimum inhibitory concentrations (MIC) were about 434, 4550, and 5000 μg mL⁻¹ for S. rolfsii, whereas it was possible to calculate only EC₅₀ (about 788 μg mL⁻¹) for R. solani. In regard to in vivo experiments, Ox BP at 5000 ppm achieved good reductions for both fungal infections ranging from about 62% up to almost 90%, whereas phytotoxic effects were not detected on tomato seedlings at the 3–4 and 4–5 true leaf stages. To the authors' knowledge, this is the first report about Ox BPs antifungal performance against globally widespread soilborne diseases of tomato without detrimental effects on the host crop. However, further studies are needed to confirm the data; this paper presents a starting point for both an eco-friendly disease management approach and recycling of the organic fraction (organic C) of municipal biowastes within the circular bioeconomy framework in a self-sustainable ecosystem.