Aislamiento, caracterización e identificación de bacterias con capacidad fijadora de nitrógeno atmosférico asociadas con la rizosfera de Solanum tuberosum L. Var. Superchola

Abstract

The present research was developed with the purpose of isolating, characterizing and identifying in vitro atmospheric nitrogen-fixing bacteria associated with the rhizosphere of S. tuberosum var. Superchola; as well as to determine their effect on the growth of potato vitroplants in greenhouses. Isolates were obtained from four localities in the province of Tungurahua, which were culturally and morphologically characterized. The in vitro atmospheric nitrogen fixation capacity was determined using modified Jensen culture medium, and molecular identification was performed by PCR amplification of 16S rRNA genes. Finally, the effect of the bacterial isolates on the growth of potato vitroplants in greenhouses was determined. The results showed that in the canton of Píllaro there was the highest quantity of CFU. g-1 of soil (9.08 x 109), in the cultural characterization 87% had smooth texture, 42% flat surface, 82% smooth consistency, 42% circular shape, 84% entire margin and 95% showed brightness. In the morphological characterization of the isolates, 84% were Gram (-) bacteria and 95% were bacilli. The bacterial isolate with the highest atmospheric nitrogen-fixing potential was CC-FCAGP-BFN1 and the one with the lowest potential was CC-FCAGP-BFN15. PCR amplification of 16S rRNA genes identified the strains Pseudomonas sp. (CC-FCAGP-BFN1, CC-FCAGP-BFN16), CC-FCAGP-BFN14) and Paraburkholderia dipogonis (CC-FCAGP-BFN24), which showed a high capacity for atmospheric nitrogen fixation. Likewise, the bacterial strain CC-FCAGP-BFN1 (Pseudomonas sp.) was the only one that increased leaf area, fresh and dry mass and leaf area index of S. tuberosum vitroplants. Based on the above results, four bacterial strains were identified from the rhizosphere of S. tuberosum, one of which was the most promising for favoring vegetative growth due to its high capacity to fix atmospheric nitrogen.