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

Abstract

Soybean bradyrhizobia, <it>Bradyrhizobium japonicum</it> and <it>Bradyrhizobium elkanii</it> 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 <it>B.</it><it>japonicum</it> and <it>B. elkanii</it> significantly depended on host plants. <it>B. japonicum</it> and <it>B. elkanii</it> preferentially nodulated <it>Glycine max</it> and <it>M. atropurpureum</it>, respectively. Both bacterial species were shown to nodulate <it>G. soja</it> with similar efficiency. There was a significant divergence of DNA sequences in and around nodulation genes between the <it>B. japonicum</it> and <it>B. elkanii</it> field isolates. However, flavonoid and lipo-chitin nodulation signals were not involved in the difference in host preference of <it>B. japonicum</it> and <it>B. elkanii</it>. The ecological implications of host preference are discussed.