Souza AA de, Burity HA, Figueiredo M do VB, Silva MLRB da, Melotto M, Tsai SM. Symbiotic efficiency of Hup+, Huphr and Hup- Bradyrhizobium japonicum and Bradyrhizobium elkanii strains in cowpea cultivars. PAB. 1999;34(10):1925-1931. doi:10.1590/S1678-3921.pab1999.v34.5518