Aslinn Fernanda Martínez-Pérez

The overuse of chemical fertilizers highlights the need for sustainable alternatives, such as plant-growth-promoting bacteria (PGPB). However, bacterial inoculant performance may vary with plant species and growth conditions. This study evaluated the effects of microbial consortia combining Azospirillum brasilense, Pseudomonas putida, Bacillus sp., and Mycobacterium sp. on blue maize, broccoli, and tomato grown in commercial substrate and greenhouse soil. Consortium effects on early plant growth varied according to bacterial combination, plant species and substrate conditions. Pseudomonas putida + Bacillus sp. increased blue maize main root length by 28.45% in greenhouse soil and stem length by 44.70% in commercial substrate, while increasing tomato shoot dry weight by over 500% in greenhouse soil. Azospirillum brasilense + Bacillus sp. increased shoot dry weight by 154.06% in broccoli and 274.87% in tomato, both in commercial substrate. Results obtained with consortia containing Mycobacterium sp. provide exploratory evidence strictly under laboratory conditions. Due to the potential health risk associated with opportunistic and pathogenic species within this genus, these strains cannot be considered for agricultural applications or biofertilizer development, serving exclusively as a model for studies. Overall, these findings emphasize that PGPB consortium performance was context-dependent, emphasizing the importance of plant species, substrate conditions, and microbial composition when evaluating bacterial inoculants.

The increasing demand for food production has intensified the use of chemical fertilizers, raising concerns about their environmental impact. Plant Growth-Promoting Bacteria (PGPB) have emerged as a sustainable alternative; however, many studies are conducted under highly controlled conditions which do not accurately represent real agricultural systems. This study evaluated the effect of microbial consortia comprising of Azospirillum brasilense, Pseudomonas putida, Bacillus sp., and Mycobacterium sp. on plant growth under contrasting substrate conditions (commercial substrate and greenhouse soil). Their biostimulant potential was assessed in Zea mays (blue maize), Brassica oleracea (broccoli), and Solanum lycopersicum (tomato). The assessment included measurements of root and shoot elongation as well as dry biomass. The results demonstrated that microbial consortia significantly (p=0.01) improved plant growth compared to the control across all species. Among the treatments, the consortium Pseudomonas putida + Bacillus sp. had the best results by presenting significantly (p=0.01) higher values in root length, stem growth, and dry weight in both substrate types. Additionally, consortia containing Mycobacterium sp. demonstrated enhanced performance in greenhouse soil, particularly in biomass accumulation for Zea mays and Brassica oleracea. These results highlight the importance of selecting appropriate microbial combinations and validating their performance in environments that reflect practical agricultural conditions.