The elite strain INPA03-11B approved as a cowpea inoculant in Brazil represents a new Bradyrhizobium species and it has high adaptability to stressful soil conditions

The strain INPA03-11BT, isolated in the 1980s from nodules of Centrosema sp. collected in Manaus, Amazonas, Brazil, was approved by the Brazilian Ministry of Agriculture as a cowpea inoculant in 2004. Since then, several studies have been conducted regarding its phenotypic, genetic, and symbiotic characteristics under axenic and field conditions. Phenotypic features demonstrate its high adaptability to stressful soil conditions, such as tolerance to acidity, high temperatures, and 13 antibiotics, and, especially, its high symbiotic efficiency with cowpea and soybean, proven in the field. The nodC and nifH phylogenies placed the INPA strain in the same clade as the species B. macuxiense BR 10303T which was also isolated from the Amazon region. The sequencing of the 16S rRNA ribosomal gene and housekeeping genes, as well as BOX-PCR profiles, showed its potential as a new species, which was confirmed by a similarity percentage of 94.7