Abstract

ANGELES-NUNEZ, Juan Gabriel  and  CRUZ-ACOSTA, Teresa. Isolation, molecular characterization and evaluation of nitrogen-fixing strains in promoting the growth of beans. Rev. Mex. Cienc. Agríc [online]. 2015, vol.6, n.5, pp.929-942. ISSN 2007-0934.

Legumes like beans and soybeans play an important role in crop rotation, thanks to the process of biological nitrogen fixation which is carried out through the symbiotic plant-microorganism interactions. Finding and obtaining strains of microorganisms capable of fixing nitrogen efficiently from the soil and promote the growth of legumes of agronomic interest is essential to meet the challenges of modern agriculture that involves increasing agricultural products, reducing the consumption of fossil energy and the emission of greenhouse gases generated by the excessive use of nitrogen fertilizers. The objective of this study was to isolate nitrogen fixing strains and growth promoters, from nodules of Glycine max L. (soybean) and Pachyrhizus erosus (jicama) and evaluate their promoting effect Phaseolus vulgaris (bean). In this work, molecular biology, physiology and biochemistry techniques were used to characterize strains isolated from soy andjicama for growth promotion. The molecular identification indicates that strain isolates from soy corresponded to Ramlibacter sp., (INI26-13), Sinorhizobium sp., (INI43-13), Sinorhizobium fredii (INI51-13), while the strain isolates from jicama corresponded to Bradyrhizobium japonicum (INI13-13). The promoter capability of these isolates were studied under greenhouse conditions in seedlings of Phaseolus vulgaris (bean), inoculated with a bacterial suspension with 10⁸ CFU / ml. The seedlings were harvested 18 days after inoculation and separated into stems and roots for study. Stems did not present changes in dry weight, however in root increased in the treatment with Ramlibacter sp., (INI26-13). It was observed the presence of nodules in the roots of all treatments; however, was the treatment with Ramlibacter sp. (INI26-13) presented the highest number of nodes. The carbohydrate profile content in roots was modified by differentially in all treatments and only stems from treatment with strain Ramlibacter sp. (INI26-13) showed increases in the content of glucose, fructose and starch. The results obtained in this work are discussed in terms of the role that organisms of growth promoters in modern agriculture.

Keywords : Phaseolus vulgaris; Ramlibacter sp.; carbohydrates; growth promoting bacteria.