Promoción del crecimiento en algodón por bacterias endófitas diazotróficas

Abstract

Endophytic bacteria can stimulate nutrient uptake and plant growth through diverse biochemical and physiological mechanisms; however, studies in cotton (Gossypium hirsutum L.), a crop of high economic relevance in Brazil, remain limited. In this context, the objective of this study was to isolate, characterize, and evaluate free-living diazotrophic strains, determining their functional potential in vitro. A total of 77 strains were obtained from three cultivars grown in Sapezal-MT (TMG47B2RF, TMG44B2RF, and FM985GLTP), using NFb medium (nitrogen-free semi-solid medium) and YMA (yeast extract mannitol agar). The strains were evaluated for nitrogen fixation, indole-3-acetic acid (IAA) production, phosphate and potassium silicate solubilization, and in vitro plant growth promotion in TMG47B2RF under 50 % of the recommended N dose, in a completely randomized design with three replications. Data were subjected to multivariate analysis. Among the evaluated strains, 61 showed nitrogen fixation ability and 20 produced IAA above 3.87 µg.mL⁻¹. Strains AL263 (IAA), AL046 (K₂SiO₄), and AL226 (N and Ca₃(PO₄)₂) stood out. Multivariate analysis identified AL232 and AL039 as the most promising strains, promoting significant increases in shoot and root biomass even under 50 % N reduction, with performance comparable to the 100 % N control and to Azospirillum brasilense Ab-V5. These results demonstrate that native multifunctional endophytic strains can sustain cotton growth under reduced nitrogen fertilization, highlighting their potential as a basis for the development of more efficient and sustainable bioinoculants.