PS 20-1 - CANCELLED - Selection effects on mycorrhizal responsiveness in intermediate wheatgrass

Abstract: Incorporation of innovative management practices is needed to further improve soil health and increase sustainability in agroecosystems. Use of novel perennial food crops and a better understanding how these crops interact with the soil microbiome could lead to sustained productivity as well as increased water infiltration, nutrient retention, organic matter formation, and carbon sequestration. The aim of this project was to investigate the how selection for desirable agronomic traits in a novel perennial grain and forage crop (Thinopyrum intermedium; intermediate wheatgrass (IWG)) has altered responsiveness to arbuscular mycorrhizal (AM) fungi. AM fungi are important because they are plant mutualists that can ameliorate detrimental environment stressors through increased resource (water and nutrient) acquisition and plant defense, as well as contribute to soil health metrics like aggregate stability. In the greenhouse, IWG seedlings from five populations with varying degrees of selection pressure were grown in sterile soil or in soil inoculated with a mix of AM fungi isolated and cultured from a Kansas Remnant prairie. Above and belowground biomass was harvested, dried, and weighed after 9 weeks of growth. Mycorrhizal responsiveness (ratio of biomass produced in sterile soil to biomass in the presence of AM fungi) was calculated for aboveground, belowground, and total biomass.

Inoculation with AM fungi did not interact with IWG generation to alter aboveground or total biomass production. Root biomass was marginally affected by inoculation, and there was a trend for more recent generations (greater selection pressure) to have more root biomass in the presence of AM fungi. Regression analysis did not reveal a significant relationship between selection pressure and shoot mycorrhizal responsiveness. However, mycorrhizal responsiveness of the roots did significantly increase with selection pressure, and this led to a marginal positive impact of selection pressure on mycorrhizal responsiveness of total biomass. These results suggest that IWG mycorrhizal responsiveness is increasing with increased selection pressure. This has important implications for soil health and agroecosystem sustainability. Further studies will provide insight into the possibility of biotic soil amendments that improve IWG performance and increase soil health, as well as inform breeding programs of the impacts of the selection process beyond typical agronomic trait responses. Results will also be used as the foundation for future studies on how different IWG genotypes respond to AM fungi, identification of traits linked to AM fungi responsiveness, and the potential to select for varying degrees of AM responsiveness in IWG.