I got to write a commentary on this great paper from Annet Westhoek et al., with Phil Poole and Euan James, whose work I’ve appreciated in the past, among the authors. They provide overwhelming evidence that peas greatly reduce support to nodules containing a rhizobia mutant with about 25% of normal nitrogen fixation, only when other nodules on the same plant contain a more-beneficial strain. My commentary discusses some of the challenges in applying those results to the development of cultivars that would impose strong enough selection for greater mutualism in rhizobia to significantly benefit future crops grown in the same soil. Although this won’t be easy and may not be possible, I think it’s a more-promising approach than (for example) genetically engineering legume crops to exclude all but a super-beneficial inoculum strain, or making cereal crops host rhizobia, and expecting those arrangements to be evolution-proof.