Sorghum - Bioenergy Crop Plants - page 497

the divergence of the major cereal crops from a common ancestor. Completion of the whole genome
sequencing project in 2009 will exponentially increase the sequence data available for Sorghum spp.
and will provide valuable information on cereal domestication in the African continent, an event that
appears to have occurred independently of other continents although by similar reinforced selective
pressures. In a way, sorghum genome sequencing will close a biographic triangle into the knowledge
of the polymorphism shared before the divergence of these important grasses and ultimately in the
understanding of the evolution in cereals crops among Africa, the Americas, and Asia. The tenets
of colinearity and microlinearity of grass genomes mean that our knowledge of other cereals and
their evolutionary ties will also greatly improve. Because of their economic and scientific value,
cereal genomes have been studied over the last 15 years using highly advanced technologies. The
similarity at the DNA level makes it possible to use comparative genetics to look for particular
genes of unknown sequence among the genomes with the aim of using that information to develop
new varieties or discovering new genes that could have a potential impact on traits that are of global
importance (e.g., food quality and drought resistance).
Sweet sorghum has long been known to be an excellent source of sugar which can easily be
fermented and distilled into fuel-grade ethanol. The main factor keeping sweet sorghum from
competing with corn as a fuel crop is the lack of an established production method. Mechanically
harvesting sweet sorghum requires either a specialized harvester capable of extracting the sugary
juice from the stalks in the field or a modified sugarcane harvester and a large nearby pressing
facility. The juice must be quickly fermented to prevent degradation of the sugars in the juice. Also,
the costs associated with transportation of the crop to the mill will be the major limiting factor for
where sweet sorghum can be profitably grown. Varieties that have higher sugar contents per ton of
biomass will be more efficient to process and haul to the mill.
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