CAPACITY OF ENDOPHYTIC DIAZOTROPHIC BACTERIA ISOLATED FROM MAGUEY TO SOLUBILIZE P AND Fe

Abstract

Plant growth promoting bacteria are natural inhabitants of the soil and the interior of plant tissues and are capable of promoting the growth and productivity of crops. When these bacteria can be isolated and multiplied in the laboratory, they have a high potential to be commercialized and used to improve the yield and health of crops. In this study, the isolation from maguey of endophytic diazotrophic bacteria with the capacity to solubilize phosphate and iron was carried out. Maguey leaves of the Púa Larga, Ayoteco, Manso, Carricillo and Chalqueño varieties were collected at the San Isidro maguey producer ranch, in the southwest of Nanacamilpa de Mariano Arista, Tlaxcala, Mexico. Isolation of endophytic bacteria was carried out using the ELMARC selective medium, and subsequent molecular identification was carried out by amplifying a fragment of the 16S ribosomal subunit. Once the identification of the bacteria was carried out by comparing the amplified sequences against the NCBI database, an evaluation of the capabilities of the bacteria to fix nitrogen and solubilize phosphate (P) and iron (Fe) was carried out based on the ARA (Acetylene Reduction Assay), Vanadate-Molybdate and Chromium Azurol Sulfonate (CAS) techniques, respectively. The ARA tests verified the diazotrophic nature of the selected bacteria in the ELMARC medium. The qualitative CAS tests showed that, of 18 isolated strains, 12 showed high capacity to produce siderophores. Afterwards, the identification of the chemical nature of these molecules and the quantitative biochemical tests carried out, made it possible to verify that the strains of Bacillus mojavensis (Bamo) and Leclercia sp. (Lesp2), with values of 0.669 and 0.637 mg mL-1, respectively, were the highest producers of catecholate-type siderophores at 24 h, while Erwinia tasmaniensis (Erta) and Enterobacter sp. (Ensp1), stood out for being the best phosphate solubilizers, achieving respective activities of 56.48 and 49.51 mg L-1 at 96 h.