Native rhizobia and their role in the nodulation, growth, and development of Leucaena leucocephala seedlings

Objective: To evaluate the effect of native rhizobial strains on nodulation, growth, dry biomass production, total nitrogen (N) and carbon (C) content in plant tissue, as well as nitrogenase activity in seedlings of Leucaena leucocephala. Design/Methodology/Approach: The study followed a completely randomized design. Seeds of L. leucocephala were germinated in an inert substrate, and six treatments were evaluated, corresponding to native rhizobial strains and an uninoculated control. Plants were harvested at 45, 75, and 105 days, and the following parameters were measured: (i) total number of nodules, (ii) plant height (root and shoot), (iii) dry plant weight, (iv) carbon and nitrogen content in dry biomass, and (v) nitrogenase enzyme activity. Results: Treatments with strains 40, 41-2, and 46 showed the highest number of nodules at 75 days. At 105 days, plants inoculated with strain 74 had a significantly higher average dry biomass (p < 0.001). The average nitrogen content was significantly higher (p < 0.0001) in treatments with strains 26, 34b, 46, and in control. No significant differences were observed in carbon content among treatments. Nitrogenase activity was confirmed in all inoculated treatments but was absent in control. Limitations/Implications: The results obtained with native Rhizobium sp. strains highlight their potential to enhance biological nitrogen fixation in Leucaena leucocephala, which could contribute to the development of more sustainable agroforestry systems, especially in nitrogen-deficient soils. Findings/Conclusions: This study highlights the potential of certain native rhizobial strains for inoculating L. leucocephala, enhancing its growth and development. However, further research under field conditions is needed to confirm these findings.