The root-nodule symbiosis between Sarothamnus scoparius L. and its microsymbionts

When nitrogen fixing root nodules are formed, Sarothamnus scoparius (broom) is inoculated with its microsymbionts. Nodules studied under light and ele ctron microscopy exhibited typical indeterminate nodule histology with apic al, persistent meristem, age gradient of nodule tissues, and open vascular bundles, and also with some particular features such as: the presence of mi totic activity in the infected meristematic cells, lack of infection thread s, distribution of bacteria by process of host cell division, and occurrenc e of a large bacteroid zone only with infected cells. The results of cross- inoculation tests have shown a broad host range for S. scoparius microsymbi onts including not only the native host but also species such as: Lupinus l uteus, Ornithopus sativa, Lotus corniculatus, Genista tinctoria, Chamaeciti sus ratisbonensis, Macroptilium atropurpureum, and Phaseolus vulgaris. In a ddition, our data established a close symbiotic relationship of S. scopariu s nodulators to Bradyrhizobium sp. (Lupinus) by comparison of the partial s equence of nodC gene of the strain CYT7, specific for the broom, to those f rom Bradyrhizobium sp. (Lupinus) strain D1 and others available in the publ ic databases.