Diversity of Photosynthetic Bradyrhizobium Strains from Stem Nodules of Aeschynomene Species

摘要: Tropical legumes of the genera Sesbania and Aeschynomene are known to form nitrogen-fixing nodules on their stems. Because high N2-fixing potential, these plants successfully used as green manure in paddy-fields significantly improve rice yield (Ladha et al., 1988; Ndoye, 1990). In both genera, nodule formation occurs at predetermined sites which always correspond root primordia present all along stem (Dreyfus Dommergues, 1981). rostrata is be associated with Rhizobium Azorhizobium, latter genus being very specific this species 1988). comprises about 250 tropical species, more than 20 bear stem-nodules. According nodulation, divided into three groups: first group (eg. Ae. Americana, elaphroxylon) only nodulated roots or submerged part stem. The second Afraspera, nilotica) third Indica, sensitiva) comprise stem-nodulating species. They differ by cross-inoculation patterns accessibility infection stem, profusely (Alazard, 1985; Alazard Duhoux, typical slow-growing strains Bradyrhizobium 1985). Until recently, heterogeneous includes has not been except that nodulating soybean (Glycine max) conventionally called japonicum. At least DNA homology groups have differentiated (Hollis Recently, Kuykendall al. (1992) proposed a new elkanii for members homolgy II. japonicum closely related purple non-sulfur photosynthetic bacterium Rhodopseudomonas palustris (Young 1991) Blastobacter denitrificans Afipia Nitrobacter (Willems Collins, 1992; Young, 1992). Moreover, strain BTAil isolated from indica (group III) was shown (Evans Although had physiological growth properties were considered characteristic Bradyrhizobium, it also recently belong Bradyrhizobium-Rhodopseudomonas rRNA cluster 1991).