Packer, Daniel (2011-05). High-biomass sorghums for biomass biofuel production. Doctoral Dissertation.
High-biomass sorghums are being developed as a dedicated energy crop for biofuels. Their high biomass yields provide large quantities of structural carbohydrates (cellulose, lignin, etc.) for energy production. Sorghum improvement for applications such as grain or fodder production is well established, but development of high-biomass sorghums for biofuels is not. Thus the objectives of this research were to develop information on sorghum improvement methods and criteria for high-biomass sorghums including marker-assisted selection, use of exotic germplasm, heterosis, and GxE variability of biomass composition.
Marker-assisted selection was compared to testcross selection for identifying photoperiod-insensitive (PI) experimental lines that yield photoperiod-sensitive (PS) hybrids within the Ma1/Ma5/Ma6 hybrid production system. High-biomass sorghums are PS and the Ma1/Ma5/Ma6 hybrid production system produces PS hybrids with PI parents by manipulating alleles at the Ma1, Ma5 and Ma6 sorghum maturity loci. Four hundred eighty three sorghum lines were genotyped at the Ma1 and Ma5 loci to predict their hybrid photoperiod reactions and testcrossed to establish their actual hybrid photoperiod reactions. Ma1/Ma5 marker selections for lines producing PI hybrids were reliable and could be used to discard such lines. Ma1/Ma5 marker selections for lines producing PS hybrids were not reliable and identification of such lines will require testcrossing or potentially, genotyping at Ma6 or other additional loci.
An attempt was made to determine whether meaningful relationships exist between the passport data (geographic origin) of exotic sorghum accessions and high-biomass desirability. Such a relationship could be used to prioritize exotic sorghum accessions for breeding evaluations. Seventeen hundred ninety two exotic sorghum accessions from 7 different geographic origins were evaluated for high-biomass desirability in 3 environments. Significant relationships between passport data and high-biomass desirability were identified within environments but were not applicable across environments because of large GxE interactions. A larger sampling of environments will be needed to understand and establish reliable passport data and high-biomass desirability GxE patterns.
High-parent heterosis can improve yields in high-biomass sorghums and hybrid entries derived from high-biomass sorghum pollinators and grain sorghum females were evaluated for biomass heterosis. Grain sorghum females enable commercial seed production of high-biomass sorghums. Moderate levels of biomass high-parent heterosis were widely available in the hybrids. Heterosis and biomass yields were maximized in specific hybrid combinations and were subject to GxE interactions.
Biomass composition (percent cellulose, hemicellulose, etc.) affects the conversion efficiency of biomass to liquid fuels and may be altered via breeding selections. Breeding methods and genotype recommendations for biomass composition will require consideration of GxE variability. The biomass composition of 12 sorghums grown across 5 environments was estimated using Near-Infrared Spectroscopy to identify GxE patterns. Significant GxE interactions for biomass composition were identified, but most compositional variability was attributable to environmental differences. Differences between genotypes for compositional traits were small (1-3 percent), but may prove important with large-scale biomass processing.