The Diversity of Culture-Dependent Gram-Negative Rhizobacteria Associated with Manihot esculenta Crantz Plants Subjected to Water-Deficit Stress

There is a lack of studies on the root-associated bacterial microbiome of cassava plants. The identification and characterization of rhizobacteria can contribute to understanding the adaptation of the agriculturally important crop plants to abiotic stress. Rhizobacteria play a significant role in plants, as they can alleviate the drought stress by various mechanisms that enhance the plant growth under these stressor conditions. In this study, Gram-negative bacterial strains from the plant rhizosphere of cassava Manihot esculenta Crantz CIAT MCOL1734 variety subjected to water deprivation were isolated, characterized according to their morphological properties, and then identified by VITEK® 2. An increase in the diversity, abundance, and species richness of Gram-negative rhizobacterial community was found in cassava plants subjected to water-deficit stress. In total, 58 rhizobacterial strains were isolated from cassava plants. The identification process found that the bacteria belonged to 12 genera: Achromobacter, Acinetobacter, Aeromonas, Buttiauxella, Cronobacter, Klebsiella, Ochrobactrum, Pluralibacter, Pseudomonas, Rhizobium, Serratia, and Sphingomonas. Interestingly, Pseudomonas luteola and Ocrhobactrum anthropi were rhizobacteria isolated exclusively from plants submitted to drought conditions. The cassava roots constitute a great reservoir of Gram-negative bacteria with a remarkable potential for biotechnological application to improve the drought tolerance of plant crops under water-deficit conditions.