Lu Ling

The paper uses molecular clock dating with non-symbiotic Bradyrhizobium relatives to show nodulation and legumes emerged around 90-80 million years ago.

This paper identifies free-living Bradyrhizobium as the ancestral state of nitrogen fixation, showing that symbiotic nitrogen fixation evolved multiple times independently from free-living ancestors.

The paper expands the diversity of nod-free Bradyrhizobium strains and shows that NF-independent nodulation is common in this supergroup.