Scatter plots for a subset of the regression models listed in Additional file 3. Ethanol yield predicted by the explanatory variables labeling the y-axis are plotted over observed ethanol yield from maize stover samples treated with the pretreatment-Rapid SSF assay. Regressions were performed on variety means (n = 12). Units for both axes are g ethanol per g dry maize stover. Varieties carrying the brown-midrib-3 mutation are symbolized by triangles.