Inoculation with growth-promoting microorganisms and their impact on the initial development of maize seedlings (Zea mays L.)

Early seedling growth is a key determinant of successful maize crop establishment, and the use of plant growth-promoting microorganisms represents a sustainable strategy to enhance early plant development. This study evaluated the individual and combined effects of rhizogenic fungi and bacteria on the early growth of two maize hybrids under greenhouse conditions and examined the relationship between root and shoot development. The hybrids Dekalb-357® (white maize) and Dekalb-7500® (yellow maize) were subjected to five treatments: an uninoculated control, T. asperellum, B. subtilis (Baktillis®), a combination of T. asperellum + B. subtilis, and Bactiva®, a commercial formulation containing Trichoderma spp., Bacillus spp., Ascophyllum nodosum, and fulvic acids. Treatments were applied to seeds prior to planting. The experiment was arranged in a completely randomized design with 10 replicates, resulting in a total of 100 experimental units). At 32 days after planting, emergence percentage, shoot and root growth variables, and root colonization by Trichoderma spp. were evaluated. Rhizogenic inoculation produced variable responses depending on the maize hybrid and treatment. Although emergence was slightly reduced, inoculation with Trichoderma spp., B. subtilis, and commercial formulations enhanced vegetative growth, increasing plant height, stem diameter, leaf number, and biomass accumulation. Root colonization by Trichoderma spp. was effective, particularly in treatments with Bactiva® and T. asperellum. The hybrid DK-357® exhibited early symptoms of phosphorus deficiency, whereas DK-7500® showed more vigorous growth. These findings underscored the importance of genotype-microorganism interactions and environmental conditions in determining inoculant effectiveness and highlight the need to consider genotype-specific responses when designing strategies to improve crop establishment and early vigour.