Phylogenetic and population structure of the nod-free but nodulating Bradyrhizobium phylogroup
we sequenced 208 new PB members predominantly associated with rice. The extended PB phylogroup comprises three main clades: a basal clade with significant expansion of its diversity, followed by the diversification of a singleton clade from a new clade exclusively represented by our strains. Our strain collection expands the phylogenetic and ecological diversity of the nod-free but nodulating Bradyrhizobium and shows that the NF-independent nodulation of Aeschynomene is a common trait of this phylogroup, in contrast to the photosynthetic trait originally thought as its unifying feature.