Bacillus subtilis and Rhizophagus intraradices Improve Vegetative Growth, Yield, and Fruit Quality of Fragaria × ananassa var. San Andreas

Strawberry cultivation requires strategies that maintain or improve its yield within a scheme in which reducing fertilizers and other chemical products can make its consumption safer and more environmentally friendly. This study aims to evaluate the effect of <i>Bacillus subtilis</i> and <i>Rhizophagus intraradices</i> on strawberry growth, yield, and fruit quality. <i>B. subtilis</i> and <i>R. intraradices</i> were inoculated and co-inoculated under three fertilization levels of 225-100-250, 112-50-125, and 0-0-0 kg∙ha^-1 of N, P₂O₅ and K₂O. Vegetative growth was evaluated in plant height (cm), leaf area (cm²), aerial fresh weight (g), aerial dry weight (g), and plant coverage (%) variables. Fruit quality parameters such as total acidity (g∙100 mL^-1), soluble solids (Brix°), and firmness (kg) were also determined, as well as the number of fruits per m² and yield (t∙ha^-1). The results showed that the pre-treatment of root immersion in a nutrient solution with <i>B. subtilis</i> and the fractionation of 6 L <i>B. subtilis</i> inoculation per plant at a concentration of 10⁷ CFU∙mL^-1, in combination with 225-100-250 kg∙ha^-1 of N, P₂O_5, and K₂O, achieved the highest accumulation of dry matter (12.9 ± 1.9 g∙plant^-1), the highest number of fruits (28.2 ± 4.5 fruits∙m^-2), and the highest yield (7.2 ± 1.4 t∙ha^-1). In addition, this treatment increased the soluble sugar content by 34.78% and fruit firmness by 26.54% compared to the control without inoculation. This study highlights the synergistic effect of mineral nutrition and microbial inoculation with <i>B. subtilis</i> in increasing strawberry yield and fruit quality.