Isolation and evaluation of endophytic bacteria from root nodules of Glycine max L. (Merr.) and their potential use as biofertilizers

  • Arely A. Vargas-Díaz CONACYT−Colegio de Postgraduados, Champotón, Campus Campeche. Ctra. Federal Haltunchén-Edzna km 17.5. Sihochac, Champotón, 24450 Campeche
  • Ronald Ferrera-Cerrato Colegio de Postgraduados, Posgrado de Edafología. Campus Montecillo, 56230 Texcoco
  • Hilda V. Silva-Rojas Colegio de Postgraduados, Posgrado de Recursos Genéticos y Productividad. Campus Montecillo 56230 Texcoco
  • Alejandro Alarcón Colegio de Postgraduados, Posgrado de Edafología. Campus Montecillo, 56230 Texcoco
Keywords: Bradyrhizobium, co-inoculation, free-living endophytic bacteria, endophytic symbiotic bacteria, plant growth promotion, soybean, symbiosis


Aim of study: To isolate and characterize endophytic bacteria inhabiting soybean root nodules collected from two tropical cropping systems in Mexico, and to evaluate the bacterial effects in soybean plants under controlled conditions.

Area of study: The study was carried out at two locations (San Antonio Cayal and Nuevo Progreso municipalities) of Campeche State, Mexico.

Material and methods: Two experimental stages were performed: 1) isolation, morphological and biochemical characterization, and molecular identification of endophytic bacteria from root-nodules of four soybean varieties grown at field conditions; and 2) evaluation of the effects of endophytic isolates on soybean growth and nodule development, and the effects of bacterial co-inoculation on soybean plants, under controlled conditions.

Main results: Twenty-three endophytic bacteria were isolated from root nodules, and identified as Agrobacterium, Bradyrhizobium, Rhizobium, Ensifer, Massilia, Chryseobacterium, Enterobacter, Microbacterium, Serratia, and Xanthomonas. Under controlled conditions, Rhizobium sp. CPO4.13C or Agrobacterium tumefaciens CPO4.15C significantly increased the plant height (46% and 41%, respectively), whereas Bradyrhizobium sp. CPO4.24C promoted the nodule formation (36 nodules/plant). The co-inoculation of B. japonicum USDA110 and Bradyrhizobium sp. CPO4.24C enhanced plant growth, height (33.87 cm), root nodulation (69 nodules/plant) and N-fixation (3.10 µmol C2H4 h-1 plant-1) in comparison to the negative control.

Research highlights:  Results suggest that the native Bradyrhizobium sp. CPO4.24C may be used as a biofertilizer directed to developing sustainable soybean cropping at tropical regions.


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How to Cite
Vargas-DíazA. A., Ferrera-CerratoR., Silva-RojasH. V., & AlarcónA. (2019). Isolation and evaluation of endophytic bacteria from root nodules of Glycine max L. (Merr.) and their potential use as biofertilizers. Spanish Journal of Agricultural Research, 17(3), e1103.
Soil science