New insights into municipal biowaste derived products as promoters of seed germination and potential antifungal compounds for sustainable agriculture

BACKGROUND: Municipal biowaste management may generate a negative impact on the environment; therefore, their biomasses could be valorised as an alternative feedstock to fossils to produce high performance compounds useful for agricultural applications. The main objective of this study was to evaluate the potential agricultural applications of bioproducts (BPs) obtained by alkaline hydrolysis of the solid anaerobic digestate of municipal biowastes (ADMBW) and of one oxidized (ozonized) product (ADMBW BP OX). Both products were chemically characterized and used for agricultural in vitro assays. RESULTS: BP preparations were tested for their potential effect as enhancers of seed germination process using five concentrations (1, 10, 100, 1000, and 5000 mg L⁻¹) and three different species: cress (Lepidium sativum), tomato (Solanum lycopersicum), and lettuce (Lactuca sativa L.). At this aim several germination indices were calculated to establish the priming effect of these substances on the selected seeds. Moreover, the potential in vitro antifungal effects of BPs at three concentrations (100, 1000, and 5000 mg L⁻¹) on many dangerous fungal phytopathogens of economically important cultivated crops were evaluated and compared to Benzothiadiazole, one of the most-used plant disease suppressants. Results show that these ADMBW derived BPs exert a seed specie-specific positive effect on germination process, inducing better performances in the several calculated indices at all the concentration tested, except for the ADMBW BP OX 5000 mg L⁻¹, which showed at the highest concentration a strong phytotoxic effect on tomato seeds. CONCLUSIONS: The fungicidal potency of ADMBW BP OX was for the first time clearly demonstrated on multiple targets as Botrytis cinerea, Sclerotinia sclerotiorum, Monilia sp., Sclerotium rolfsii, and Phytophthora nicotianae, by calculating their relative EC₅₀ and, when it was possible, also EC₉₅ and MIC values. These results are of great impact in the actual historical moment, as from a biowaste as DMBW, which is worldwide constantly produced, may be possible to obtain agrochemicals and fertilizers without the usual feedstocks, which are more and more expensive.