Phylogeny, plant species, and plant diversity influence carbon use phenotypes among Fusarium populations in the rhizosphere microbiome

Authors: LEBLANC, NICHOLAS - University Of Minnesota; ESSARIOUI, ADIL - University Of Minnesota; KINKEL, LINDA - University Of Minnesota; Kistler, Harold

Submitted to: Phytobiomes Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2017
Publication Date: 11/1/2017
Citation: LeBlanc, N.R., Essarioui, A., Kinkel, L.L., Kistler, H.C. 2017. Phylogeny, plant species, and plant diversity influence carbon use phenotypes among Fusarium populations in the rhizosphere microbiome. Phytobiomes Journal. 1(3):150-157. https://doi.org/10.1094/pbiomes-06-17-0028-r.
DOI: https://doi.org/10.1094/pbiomes-06-17-0028-r

Interpretive Summary: While historically, plant pathologists have focused on understanding fungi that cause disease in plants, many fungi are known to be helpful to plant health and vigor. However, little is known about the overall composition of fungi inhabiting the soil or growing within healthy plants. This study characterizes the soil fungi (Fusarium species) associated with soil at the base of two native plant species. These plant species were grown alone, simulating agricultural monoculture, or together with several other species, simulating more natural grassland environments. Both the individual plant species as well as the plant context (monoculture versus polyculture) greatly influences the types and diversity of Fusarium that exist in these plant associated soils and the types of nutrients they utilize. These observations likely will influence thinking on cropping systems arising from agricultural monoculture and inter-cropping and their impact on fungal soil communities and plant health. The primary users of the research in this publication will be other scientists engaged in research to improve disease management on small grain crops.

Technical Abstract: Carbon use by microorganisms in the rhizosphere microbiome has been linked to plant pathogen suppression and increased mineralization of soil nutrients for plant uptake, however factors that influence carbon use traits are poorly understood for most microbial groups. This work characterized the relationships of phylogeny, plant species, and plant diversity with carbon use among fungi in the genus Fusarium from rhizosphere soil. Eighty-four randomly collected Fusarium isolates were cultured from the rhizosphere of the perennial plants Lespedeza capitata and Andropogon gerardii, maintained as long-term monocultures or growing in 16-plant species polycultures. For each isolate, a portion of the RPB2 locus was sequenced for phylogenetic analyses and growth on 95 carbon substrates was measured using Biolog SF-P2 plates. Similarity in carbon use among isolates decreased with increasing genetic distance and there were differences in niche width (i.e. number of carbon substrates used) and growth on preferred substrates (i.e. mean growth on the 5 carbon substrates supporting the greatest growth) among isolates within 2 predominant phylogenetic clades. Carbon use phenotypes also varied with plant species and the diversity of the surrounding plant community. Within each of the 2 predominant clades, niche width was greater among Fusarium isolates from the rhizosphere of L. capitata than A. gerardii. The correspondence of phylogeny with carbon use suggests changes in Fusarium community composition may lead to the differential use of carbon substrates in the rhizosphere, while the effects of plant species and diversity suggest variation in plants communities may also correspond to variation in carbon use by these fungi. In addition, the consistent effect of plant species on niche width within different clades, provides evidence that the rhizosphere environment of the 2 plants selects for particular phenotypes, rather than promoting the presence of clades with those phenotypes. Overall, this research shows the dynamics of plant and fungal communities are likely to influence carbon use in the rhizosphere and consequently processes related to this trait, such as soil nutrient cycling and pathogen suppression.