Abstract

FLOREZ-MARQUEZ, Jessica D.; LEAL-MEDINA, Gloria I.; ARDILA-LEAL, Leidy D.  and  CARDENAS-CARO, Diana M.. Isolation and characterization of rhizobacteria associated with rice crops (Oryza sativa L.) in Norte de Santander (Colombia). Agrociencia [online]. 2017, vol.51, n.4, pp.373-391. ISSN 2521-9766.

The plant-growth promoting rhizobacteria are recognized and studied for their beneficial effects on several crops. Strains of the Azotobacter and Pseudomonas genera were isolated from rhizospheric soil where rice crops (Oryza sativa L.) are grown, from 10 farms located in the Zulia River’s irrigation district, Norte de Santander, Colombia. The bacterial isolation was obtained from granular soil and serial soil dilutions, which were planted on Ashby and King B agar, for Azotobacter and fluorescent Pseudomonas, respectively. Forty-two isolates were stored in vials with a sterile saline solution (0.85 % NaCl) in a refrigerator at 4 °C and were deposited in the Bank of Strains of the Applied Biology Research Laboratory of the Universidad Francisco de Paula Santander, Cúcuta, Colombia. The capacity to solubilize inorganic phosphate, to fix biological nitrogen, and to synthesize indoleacetic acid and siderophores were determined in all strains, in order to select isolates with potential to develop microbial inoculum. With a hierarchical clustering of the medians of the four activities, four isolations were selected because they presented the closest values to the controls designed as promising strains in the four activities, according to the similarity dendrogram. These four strains were identified as Pseudomonas putida (RzA027 and RzA035), Azotobacter chrococcum (RzA040), and Azotobacter tropicalis (RzA042), by amplification of the 16S rDNA gene.

Keywords : Azotobacter; Pseudomonas putida; phosphates solubilization; biological nitrogen fixation; indoleacetic acid; siderophores.

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