Genetic Diversity Study of Sweet Sorghum Relating to Cold Tolerance.

Sweet sorghum (Sorghum bicolor (L.) Moench), a C4 plant, shows great tolerance to warm, dry weather, and most varieties are susceptible to cold temperatures during the early growth stages.   Cold temperatures affect the germination of the sorghum seed as well and compromise stand establishment of the crop.  Because sorghum tolerates warmer temperatures than corn, the areas useful for biofuel production might be expanded.  Identification of cold tolerant varieties of sweet sorghum might permit further expansion.  Since the growth habit of sorghum allows for the production of a ratoon, or regrowth after a harvest, this leads to the ability for multiple harvests a year.  Close to three times the yield (around 30 Mt ha^-1 of dry biomass) can be produced on the same area of land as compared to switch grass because of the ratoon nature of sorghum.  The purpose of this research is to identify and map molecular markers linked to quantitative trait loci (QTLs) whose allelic variants significantly influence cold tolerance.  Plant tissues used in the DNA extraction were obtained by plants that exhibited the traits for cold tolerance in a field trial, planted in early April, collected early June.  After purification, the 50 samples were amplified through PCR with 20 different Simple Sequence Repeats (SSR) primers.  The gels were scored on a present/not-present system, and analyzed with Populations 1.2.30, and a dendrogram created.