The impacts of domestication and breeding on nitrogen fixation symbiosis in legumes

Authors: LIU, JINGE - University Of Kentucky; YU, XIAOCHENG - University Of Kentucky; QIN, QIULIN - University Of Kentucky; Dinkins, Randy; ZHU, HONGYAN - University Of Kentucky

Submitted to: Frontiers in Genetics
Publication Type: Review Article
Publication Acceptance Date: 7/31/2020
Publication Date: 8/18/2020
Citation: Liu, J., Yu, X., Qin, Q., Dinkins, R.D., Zhu, H. 2020. The impacts of domestication and breeding on nitrogen fixation symbiosis in legumes. Frontiers in Genetics. 11. Article 00973. https://doi.org/10.3389/fgene.2020.00973.
DOI: https://doi.org/10.3389/fgene.2020.00973

Interpretive Summary: Legumes are second to cereals as the most important crop family in agriculture today. One of the main features of legumes is their ability to interact with soil bacteria, called rhizobia, in a symbiotic relationship in the roots to fix atmospheric nitrogen into a form that is usable by the plant. Different legume species interact with different rhizobial species, and strains, and it is not known whether domestication, together with modern agricultural practices, have affected this interaction and efficiency. One prediction is that through the use of high fertilization practices we have selected for strains that may be less efficient in their nitrogen fixation potential. However to test this hypothesis, it will require characterizing both modern varieties, along with their wild relatives, under both natural and cultivated environments. Very few experimental studies have been done in this area of research. This review describes how legumes regulate their interactions with soil rhizobia and how domestication, breeding and agricultural practices might have affected nodulation capacity, nitrogen fixation efficiency, and the composition and function of the soil rhizobial community. It also provides a perspective on how to improve legume-rhizobial symbiosis in sustainable agricultural systems.

Technical Abstract: Legumes represent the second most important family of crop plants. One defining feature of legumes is their unique ability to form a root-nodule symbiosis wirth nitrogen-fixing soil bacteria called rhizobia. Since domestication from their wild relatives, crop legumes have been under intensive breeding to improve yield and other agronomic traits but with little attention paid to the belowground symbiosis traits. Theoretical models predict that domestication and breeding processes, coupled with high-input agricultural practices, might have reduced the capacity of crop legumes to achieve their full potential of nitrogen fixation symbiosis. Testing this prediction requires characterizing symbiosis traits in wild and breeding populations under both natural and cultivated environments using genetic, genomic, and ecological approaches. However, very few experimental studies have been dedicated to this area of research. Here, we review how legumes regulate their interactions with soil rhizobia and how domestication, breeding and agricultural practices might have affected nodulation capacity, nitrogen fixation efficiency, and the composition and function of rhizobial community. We also provide a perspective on how to improve legume-rhizobial symbiosis in sustainable agricultural systems.