Isolation, Characterization, and Selection of Bacterial Endophytes from Soybean (Glycine max) Nodules and Roots in Some Soils of Cameroon for Promoting Growth of Forage Legume Plants

Abstract

Aim: The present study aimed to isolate, characterize and select the most effective bacterial endophytes to enhance soybean growth, biomass, and yield. Methodology: Seven soil samples were collected from the rhizosphere of forage legumes in fields across three agroecological zones of Cameroon. Bacterial endophytes were isolated from soybean roots and nodules and cultured on nutrient agar. The isolates were screened for the tolerance tests, extracellular enzymatic activity, P-solubilization activity, and IAA production. The best isolates were selected using a two-factor block factorial design. Each treatment was replicated six times. Results: A total of 85 bacterial endophytes were isolated. Characterization results of 22 preselected isolates revealed an optimal growth temperature of 37°C and a pH range between 6 and 7. Furthermore, the 22 isolates solubilized inorganic phosphate, 7 produced IAA, and 8 exhibited amylase activity. PCR analysis of the nifH and nodC genes showed that the isolates possessed the nifH gene as a nitrogen fixation marker and the nodC gene as a nodulation marker. The findings show that, out of the 22 bacterial endophyte isolates, NTT1 and BOSH9 were the most effective in increasing plant height by 26.74% and 31.78%, respectively. Additionally, they resulted in an increase in biomass of 94.24% to 120.48% and an increase of 71.59% to 76.70% in grain yield compared to control treatment. Conclusion: The selected isolates significantly enhance plant growth, increase biomass, and improve soybean grain yield. However, their potential use as biofertilizers in agriculture will require further investigation under real field conditions.