Preferential nodulation of Glycine max, Glycine soja and Macroptilium atropurpureum by two Bradyrhizobium species japonicum and elkanii

Abstract

Soybean bradyrhizobia, Bradyrhizobium japonicum and Bradyrhizobium elkanii differ in various traits such as DNA fingerprint, rhizobitoxine production, indole-3-acetic acid production and uptake of hydrogenase. In this communication, we investigated whether the differences between both species extend to host preference in multistrain environments. Nodule occupancy of B. japonicum and B. elkanii significantly depended on host plants. B. japonicum and B. elkanii preferentially nodulated Glycine max and M. atropurpureum, respectively. Both bacterial species were shown to nodulate G. soja with similar efficiency. There was a significant divergence of DNA sequences in and around nodulation genes between the B. japonicum and B. elkanii field isolates. However, flavonoid and lipo-chitin nodulation signals were not involved in the difference in host preference of B. japonicum and B. elkanii. The ecological implications of host preference are discussed.