Almost all of the soybean cultivars (Glycine max L. Merr.) form nodules on their roots by infection with Bradyrhizobium japonicum. However, it has been observed that the soybean cultivars harboring nodulation conditioning genes, for instance Rj2, Rj3, and Rj4, do not form effective nodules with some strains of B. japonicum. Ishizuka et al. (1991b) classified the rhizobia isolated from field-grown soybeans into nodulation-types A, B, and C based on the compatibility with these Rj-soybean cultivars. Nodulation-type B is incompatible with Rj2 Rj3-cultivars and type C is incompatible with Rj4-cultivars. Nodulation-type A rhizobia are compatible with both Rj2 Rj3 - and Rj4-cultivars. Furthermore, the Rj-cultivars were found to prefer appropriate nodulation-type rhizobia for nodulation, that is, non-Rj-, Rj2 Rj3 -, and Rj4-cultivars prefer nodulation-types A, C, and B rhizobia, respectively (Ishizuka et al. 1991a). In the present study, in order to examine the mechanisms of preference of Rj-cultivars for rhizobial strains for nodulation, root exudates from Rj-cultivars were examined for their effects on the growth rate and chemotaxis of various types of B. japonicum strains.
All Science Journal Classification (ASJC) codes
- Soil Science
- Plant Science