Light availability and rhizobium variation interactively mediate the outcomes of legume-rhizobium symbiosis
Heath, Katy et al. (2020), Light availability and rhizobium variation interactively mediate the outcomes of legume-rhizobium symbiosis, Dryad, Dataset, https://doi.org/10.5061/dryad.hx3ffbg9s
Premise of the study: Nutrients, light, water, and temperature are key factors limiting the growth of individual plants in nature. Mutualistic interactions between plants and microbes often mediate resource limitation for both partners. In the mutualism between legumes and rhizobia, plants provide rhizobia with carbon in exchange for fixed nitrogen.
Because partner quality in mutualisms is genotype-dependent, within-species genetic variation is expected to alter the responses of mutualists to changes in the resource environment. Here we ask whether partner quality variation in rhizobia mediates the response of host plants to changing light availability, and conversely, whether light alters the expression of partner quality variation.
Methods: We inoculated clover hosts with 11 rhizobium strains that differed in partner quality, grew plants under either ambient or low light conditions in the greenhouse, and measured plant growth, nodule traits, and foliar nutrient composition.
Key results: Light availability and rhizobium inocula interactively determined plant growth, and rhizobium partner quality variation was more apparent in ambient light.
Conclusions: Our results suggest that variation in the costs and benefits of rhizobium symbionts mediate host responses to light availability, and that rhizobium variation might more important in higher-light environments. Our work adds to a growing appreciation for the role of microbial intraspecific and interspecific diversity in mediating extended phenotypes in their hosts and suggests an important role for light availability in the ecology and evolution of legume-rhizobium symbiosis.