Non-structural carbohydrate profiles and ratios between soluble sugars and starch serve as indicators of productivity for a bioenergy grass

There is a pressing need to find a sustainable alternative to fossil fuels that will not compromise food security or require heavy use of agrochemicals. Miscanthus is a perennial energy grass predominantly used for combustion but with the current advancement of ligno-cellulosic fermentation technologies there is an interest in using Miscanthus for bioethanol production. Currently, the only commercially grown genotype of Miscanthus is M. x giganteus; a high yielding, interspecific hybrid of M. sacchariflorus and M. sinensis. As M. x giganteus is a sterile triploid it cannot be used as a parent so Miscanthus breeding effort is focused on producing new interspecific varieties that out-perform M. x giganteus. The carbohydrate profiles of four genotypes of Miscanthus, including M. sacchariflorus (Sac-5), M. x giganteus (“Gig-311”). M. sinensis (Sin-11) and M. sinensis (“Goliath”) were characterised at replicated field sites in Aberystwyth, West Wales and Harpenden, South-East England. Our hypothesis was that a distinctive carbohydrate profile underlies enhanced biomass accumulation. Biomass accumulation is greatest when day-lengths and solar intensity are highest so observations were made in the middle of UK summer (July) for two years. Gig-311 had a greater abundance of fructose in its stems at both sites and both Gig-311 and Sac-5 had low abundance of starch. At both sites the highest yielding genotype was Gig-311 and Sac-5 was also high yielding at Harpenden, but performed comparatively poorly at Aberystwyth. At both sites Gig-311 had a distinctly high concentration of fructose, low starch and a high ratio of soluble sugars: starch and at Harpenden, Sac-5 was similar. We conclude that the abundance of starch and fructose and a greater partitioning of soluble sugars, relative to starch, are candidate biomarkers of productivity in Miscanthus.