Effects of Bacillus halotolerans as a Plant Growth-Promoting Rhizobacterium and Root Phytopathogen Biocontrol Agent in Solanum lycopersicum Under Field Conditions

Tomato is the most widely consumed vegetable worldwide and serves as an important source of vitamins and minerals. Using the Bacillus species as biocontrol agents and plant growth promoters is a sustainable approach to optimize production and mitigate the effects of root-infecting phytopathogenic fungi, thereby reducing reliance on chemical inputs. This study evaluated the effectiveness of a Bacillus sp.-based bioinoculant, produced in a 7 L bioreactor, for controlling root phytopathogens and enhancing tomato yields under field conditions. The trial was conducted at an experimental field of the Universidad Nacional Agraria La Molina (Lima, Peru) using a randomized complete block design with four blocks. Treatment means were compared using Tukey’s multiple range test (α = 0.05) to evaluate treatment effects. The treatments included three concentrations of the bioinoculant (10%, 20%, and 30%) derived from an initial concentration of 1 × 108 CFU/mL of a Bacillus halotolerans IcBac2.1 strain sourced from the LEMyB laboratory strain collection, a commercial biological product (1 × 109 CFU/g), and uninoculated control. Applications were made for the following four key stages of crop development: 10 days after germination, when transplanting through root dipping, 7 days after transplanting, and at the onset of flowering. In all treated groups, applications were directed to the plant crown, whereas the control group received no treatment. The evaluated variables included plant height (cm), stem diameter (mm), root disease incidence (%), chlorophyll index (SPAD), °Brix, pH, vitamin C (mg/100 g), total protein (mg/100 g) and crop yield (t/ha). The greatest plant growth-promoting effects were observed in plants inoculated with the 20% bioinoculant and in the commercial product treatment, as evidenced by increased plant height, greater fruit diameter, caliber, and length, as well as lower root disease incidence (2.86% and 1.43%, respectively). In addition, yields were highest in these treatments (29.9 and 25.2 t ha−1, respectively) compared with 14.5 t ha−1 in the control. These results indicate that a 20% B. halotolerans-based bioformulation, similar to the commercial formulation, promotes plant growth, improves agronomic performance, and reduces root disease incidence in tomato crops.