Corn, Rebecca J. (2009-12). Heterosis and Composition of Sweet Sorghum. Doctoral Dissertation. Thesis uri icon


  • Sweet sorghum (Sorghum bicolor) has potential as a bioenergy feedstock due to
    its high yield potential and the production of simple sugars for fermentation. Sweet
    sorghum cultivars are typically tall, high biomass types with juicy stalks and high sugar
    concentration. These sorghums can be harvested, milled, and fermented to ethanol using
    technology similar to that used to process sugarcane. Sweet sorghum has advantages in
    that it can be planted by seed with traditional planters, is an annual plant that quickly
    produces a crop and fits well in crop rotations, and it is a very water-use efficient crop.
    Processing sweet sorghum is capital intensive, but it could fit into areas where sugarcane
    is already produced. Sweet sorghum could be timed to harvest and supply the sugar mill
    during the off season when sugarcane is not being processed, be fit into crop rotations, or
    used in water limiting environments. In these ways, sweet sorghum could be used to
    produce ethanol in the Southern U.S and other tropical and subtropical environments.
    Traditionally, sweet sorghum has been grown as a pureline cultivar. However,
    these cultivars produce low quantities of seed and are often too tall for efficient
    mechanical harvest. Sweet sorghum hybrids that use grain-type seed parents with high sugar concentrations are one way to overcome limitation to seed supply and to capture
    the benefits of heterosis.
    There are four objectives of this research. First to evaluate the importance of
    genotype, environment, and genotype-by-environment interaction effects on the sweet
    sorghum yield and composition. The second objective is to determine the presence and
    magnitude of heterosis effects for traits related to sugar production in sweet sorghum.
    Next: to study the ability of sweet sorghum hybrids and cultivars to produce a ratoon
    crop and determine the contribution of ratoon crops to total sugar yield. The final
    objective is to evaluate variation in composition of sweet sorghum juice and biomass.
    Sweet sorghum hybrids, grain-type sweet seed parents, and traditional cultivars
    that served as male parents were evaluated in multi-environment trials in Weslaco,
    College Station, and Halfway, Texas in 2007 and 2008. Both genotype and environment
    influenced performance, but environment had a greater effect than genotype on the
    composition of sweet sorghum juice and biomass yield. In comparing performance, elite
    hybrids produced fresh biomass and sugar yields similar to the traditional cultivars while
    overcoming the seed production limitations. High parent heterosis was expressed among
    the experimental hybrids for biomass yield, sugar yield and sugar concentration.
    Additional selection for combining ability would further enhance yields and heterosis in
    the same hybrid. Little variation was observed among hybrids for juice and biomass
    composition suggesting that breeding efforts should focus on yield before altering plant

publication date

  • December 2009