Co-inoculation of arbuscular mycorrhizal fungi and Bacillus subtilis enhances morphological traits, growth, and nutrient uptake in maize under limited phosphorus availability

The use of beneficial microorganisms to enhance phosphate fertilizer use efficiency and solubilize residual phosphorus (P) is a promising strategy to improve soil P availability for plants. This study tested the hypothesis that inoculation with arbuscular mycorrhizal fungi, either alone or in combination with Bacillus subtilis, enhances maize growth and optimizes nutrient availability, particularly phosphorus. The experiment was conducted under greenhouse conditions with four replications, following an 8 × 3 factorial design. Treatments included individual inoculations with Bacillus subtilis (IPACC26), Rhizophagus clarus (RJN102A), Claroideoglomus etunicatum (SCT101A), and a commercial inoculant of Rhizophagus intraradices (Rootella BR ULTRA), as well as three co-inoculations (IPACC26 combined with each fungus) and a non-inoculated control. These treatments were combined with three levels of phosphate fertilization (0, 50, and 100% of the recommended P level). Mycorrhizal colonization improved root architecture and increased photosynthetic pigments and uptake of P and other nutrients, resulting in greater plant growth and biomass production. The most pronounced effects were observed in plants inoculated with R. clarus and C. etunicatum, either alone or in combination with B. subtilis, at the 0 and 50% P levels. At 0% P, inoculated plants accumulated significantly more biomass, with root and shoot dry mass up to 3,000% and 680% higher, respectively, than those of uninoculated plants; this effect was associated with a 1,700% increase in shoot P accumulation compared to the control. These findings highlight the potential of these inoculants as biofertilizers for more sustainable and efficient phosphorus management in maize cultivation.