Characterization of Culturable Plant Growth-promoting Bacteria Isolated from Amaranthus hypochondriacus L. Roots.

Amaranths plants grow under several abiotic stress conditions and produce high-quality edible seeds. Despite their high agronomic and nutritional potential, their endophytic bacteria have not yet been characterized. This study aimed to isolate Amaranthus hypochondriacus L. root endophytes and characterize their plant growth-promoting capacity. Twenty-six amaranth root putative diazotrophs were isolated and identified by 16S rRNA gene sequencing. Most of the isolated strains exhibited multiple plant growth-promoting traits, such as iron and phosphate solubilization and the capacity to form biofilms. Total indole production by one of the isolated bacteria, identified as Pantoea vagans, was high (124.6 μg mL-1). Four endophytes that showed coculture compatibility, identified as Lelliottia, Pantoea vagans, Pseudomonas cf. fluorescens, and Pseudomonas rhodesiae, were selected for their individual or combined (consortium) inoculation in the model plant Arabidopsis thaliana. The consortium resulted in significant increases in fresh and dry biomass accumulation in Arabidopsis plantlets. These results highlight the diversity of amaranth root endophytes and their potential as biofertilizers. Further research to verify the consortium in amaranths and other commercial crops under greenhouse and field conditions is warranted.