Utilizing mycorrhizal responses to guide selective breeding for agricultural sustainability

Abstract

Agriculture touches all aspects of society and global environmental health. Dwindling phosphorous reserves are a looming crisis for civilization, and soil erosion typically far outpaces pedogenesis. Improving plant–mycorrhizal symbioses can enhance sustainable agriculture because mycorrhizas typically improve host-plant nutrition and stabilize soils. Selective breeding of plants that gain greater benefits from mycorrhizas can provide considerable economic and environmental benefits. Our assessments demonstrate switchgrass genetic improvement increased or maintained production of two populations, and low-input breeding increased mycorrhizal responsiveness, compared to parent lines. Selecting for increased mycorrhizal reliance may be an effective strategy for more sustainable and economical agricultural production. Summary: Plant–mycorrhizal interactions are not typically assessed in crop breeding programs. Our experiment addresses this by determining host-plant outcomes of newly developed synthetic (agronomic) populations compared with parent lines, following low-input selective breeding. Assessing the potential of low-input breeding to enhance crop mycorrhizal benefits is a critical step toward more sustainable agricultural production. We compared four synthetic populations of Panicum virgatum, from a low-input biofuel breeding program at Oklahoma State University, to corresponding parent lines. Plants were grown in a greenhouse in native prairie soils that were either steam-pasteurized (nonmycorrhizal) or non-steamed (mycorrhizal). We assessed shoot and root biomass, shoot P concentration and P content, mycorrhizal growth response (MGR), and mycorrhizal phosphorous response (MPR). Importantly, we provide novel evidence that low-input selective breeding increased mycorrhizal reliance of switchgrass synthetics compared to parent lines, with implications for global agricultural systems. There are substantial opportunities for plant traits associated with increased MGR and MPR to be transferred to a wide array of crops. Our findings indicate low-input selective breeding can improve MGR and MPR. We propose these traits serve as a useful proxy for host-plant mycorrhizal reliance, facilitating successful hologenome breeding to reduce fertilizer requirements.