title: Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation.
abstract: Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11-24%) and sorghum (7-36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8-19%) and sorghum (9-27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9-21%) and sorghum (16-27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15-18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops.
authors.affiliation: Department of Genetics and Biochemistry, Clemson University Clemson, SC, USA.
authors.forename: Rajandeep S
authors.initials: RS
authors.lastname: Sekhon
authors.affiliation: Department of Agronomy, University of WisconsinMadison, WI, USA; DOE Great Lakes Bioenergy Research Center, University of WisconsinMadison, WI, USA.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Breitzman
authors.affiliation: Institute of Mathematics and Statistics, Federal University of Goiás Goiânia, Brazil.
authors.forename: Renato R
authors.initials: RR
authors.lastname: Silva
authors.affiliation: Center for Chemical Genomics, University of Michigan Ann Arbor, MI, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Santoro
authors.affiliation: Department of Soil and Crop Sciences, Texas A&M University College Station, TX, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Rooney
authors.affiliation: Department of Agronomy, University of WisconsinMadison, WI, USA; DOE Great Lakes Bioenergy Research Center, University of WisconsinMadison, WI, USA.
authors.forename: Natalia
authors.initials: N
authors.lastname: de Leon
authors.affiliation: Department of Agronomy, University of WisconsinMadison, WI, USA; DOE Great Lakes Bioenergy Research Center, University of WisconsinMadison, WI, USA.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: Kaeppler
keywords: biofeedstocks; biofuels; maize; non-structural carbohydrates; sorghum; structural carbohydrates