Multiple strains per plant and root-to-root (not seed-borne) transmission should favor rhizobia that invest in their own reproduction, rather than symbiotic N2 fixation, as analogous factors may favor pathogen virulence. But legumes can select for greater mutualism, controlling nodule O2 supply and reducing reproduction of rhizobia that fix less N 2.
Bibliographical noteFunding Information:
Thanks to Bob Rousseau for Fig. 1. Our research on this topic is supported by an NSF Graduate Fellowship, NSF grant 0212674, the Kearney Foundation of Soil Science, and the Land Institute.
- Nitrogen fixation