Felderhoff, Terry (2011-08). QTLs for Energy Related Traits in a Sweet x Grain RIL Sorghum [Sorghum bicolor (L.) Moench] Population. Master's Thesis.
Recent initiatives for biofuel production have increased research and development of sweet sorghum. Currently, the initial major limitation to integrating sweet sorghum into existing production systems is the lack of sweet sorghum hybrids adapted to industrial production systems. Hybrid development is now underway, and the application of genetic markers can be used to define the genetic basis of sugar yield and its components, as well as reduce the time required to deliver new sweet sorghum hybrids to market. The purpose of this research was to further characterize the genetic components that influence sweet sorghum productivity, agronomics, and composition. Specifically, a grain x sweet sorghum recombinant inbred line (RIL) population developed for quantitative trait locus (QTL) analysis related to sugar production was evaluated for 24 phenotypic traits including brix, percent moisture, and biomass yield across four environments. The 185 F4 RILs were derived from the parents 'BTx3197' and 'Rio', which are pithy stalk grain and juicy stalk sweet sorghums respectively. Following screening, two genetic maps were constructed with 372 and 381 single nucleotide polymorphisms (SNPs) evaluated using an Illumina GoldenGate assay. Analysis of the data in QTL Cartographer revealed a major and previously reported QTL for soluble solids on chromosome 3, but in contrast to previous studies, this QTL co-localized with other QTLs that have a negative influence on biomass and seed production. Therefore, selection for this QTL may not be advantageous. Because only a few QTLs for percent moisture were found, the results indicated that the pithy stalk phenotype does not have a major effect on percent moisture as measured in this study. Thus, breeding for high or low moisture content will be more challenging than previously expected. The absence of dominance effects indicated that brix must be high in both parents to produce high brix in the hybrid.