Figure Legends
Fig. 1 Parental genotypes grown under natural conditions host distinct microbiota. Panels: (a), principal coordinate graph based on Bray-Curtis dissimilarities; (b), Shannon diversity of samples from native parental habitats; (d), number of ASVs with differential abundance between parental habitats broken down by phylum where bars to the left indicate number of ASVs enriched in the Austin habitat, while bars to the right indicate number of ASVs enriched in the Corpus habitat. Color legends in b and d are consistent with panel a. Microbial treatments differ significantly in community composition for plants growing in the greenhouse. Panels: (d), principal coordinate graph based on Bray-Curtis dissimilarities; (e), Shannon diversity of greenhouse samples; (f), number of differentially abundant ASVs when comparing AI vs. CI soil inoculum for both native and mock treatments where bars to the left indicate the comparison for the mock treatments while bars to the right indicate native treatments. The color scheme in panels e and f are consistent with panel d.
Fig. 2 Effect of plant ecotype (E) and microbial treatment (TRT) and their interaction (E*TRT) on plant functional traits. Traits: (a), shoot biomass; (b), specific leaf area; (c), lateral root length; (d), specific root length; (e), root tissue density; (f), first order root length (data are means +S.E.).
Fig. 3 Genetic map of the Panicum hallii  RIL population with locations of significant trait QTL by microbial treatment.
Fig. 4 Tests of effect slices for significant Treatment x Marker interactions for traits in the full model analysis of QTL x treatment interactions using PROC mixed in SAS with QTL modeled on the marker nearest the QTL peak. Panels: (a), root number at 8@33.1; (b), root mass ratio at 3@74.9; (c), specific root length at 4@19.1; (d), first order root length at 9@25.6; (e), lateral root length at 7@3.4; (f), tiller number at 7@17.0; (g), root diameter at 7@2.7; (h), root number at 7@0.3; (i), shoot biomass at 9@3.9; (j), root biomass at 9@3.9; (k), root length at 9@3.9.
Fig. 5 Pairwise epistatic QTL in the P. hallii RIL population detected only under Austin Inoculated and Corpus Inoculated treatments, with plotted points indicating two-locus genotype means ± 1SE for the two loci impacting root diameter. Root diameter QTL interactions for treatments: (a) Mock Inoculated (MI); (b), Austin Inoculated (AI); (c), Corpus Inoculated (CI).