Growth promotion of tomato plants through bacteria derived from spent substrate of edible mushrooms

Tomato is one of the most widely cultivated vegetables worldwide, and Brazil is among its main producers. To meet increasing food demand, it is essential to enhance productivity sustainably. However, the excessive use of chemical fertilizers can cause environmental problems, including soil and water contamination. In this context, alternatives such as plant growth-promoting bacteria (PGPB) and organic residues, like spent mushroom substrate, have gained attention due to their agronomic and environmental benefits. Biochemical and antagonistic tests allow the identification of microorganisms capable of producing important metabolic compounds and contributing to plant development. This study aimed to evaluate, in vitro, the production of biochemical compounds by bacterial isolates obtained from mushroom substrate and to assess their potential to promote tomato growth under greenhouse conditions. Treatments were applied via foliar spraying, seed treatment, and their combination. Twenty bacterial isolates were tested for protease, cellulase, catalase, amylase, lipid hydrolysis, lipolytic activity, siderophore production, and indole-3-acetic acid (IAA) synthesis. Three isolates, BUD 5, BUD 7, and BUD 19, were selected for greenhouse experiments. Evaluated parameters included plant height, chlorophyll fluorescence (PAM), total chlorophyll content, shoot and root biomass, root length, and volume. BUD 5 showed the best performance, when applied spraying or seed treatment. In the first year, BUD 5 and BUD 19 increased root dry mass, while in the second year the control showed higher chlorophyll content after 24 hours, indicating annual variation. BUD 7 and BUD 19 also performed well in root development. These results highlight variable bacterial effects and potential to promote tomato growth under conditions.