Environmental Engineering Reference
In-Depth Information
and Fuller 2009). Crop plants were also mostly domesticated by selection of the genome for food
use. The selection of plants for energy production will require isolating and selecting for previously
ignored traits in already domesticated species or selecting previously undomesticated but promising
species (Simmons et al. 2008; Henry 2010b). Domestication of plants for food has produced many
domesticated plants with nonstructural carbohydrates (e.g., sugars and starches) that are sources of
energy for animals and humans. These carbohydrates have been exploited in the first generation
of bioenergy production from domesticated plants. Second-generation bioenergy crops are widely
recognized as those that are available to be utilized for their more abundant structural (cell wall)
carbohydrate with the potential to utilize much more of the carbon in these plants for energy. The
ancient process of plant domestication was not always a deliberate one, but the opportunity now
exists to domesticate with specific objectives and using the tools of modern science to achieve in a
few generations what previously required hundreds. Genomics provides tools for a comprehensive
analysis of the plant and the potential for selection of genotypes better suited to any given human
use. Thus, genomics is a powerful tool for use in the accelerated domestication and improvement
of plants as energy crops. Genomics may also be applied to the engineering of plant and nonplant
organisms for the conversion of plant biomass to bioenergy. The application of genomics at these
two levels may be complementary or potentially even synergistic in achieving the goal of energy-
and cost-efficient bioenergy production.
2.2 aPPlIcatIons oF GenomIcs In the develoPment
oF enerGy croPs
Genomics can be applied at many different levels in the development of plant species as bioen-
ergy crops:
• In identifying higher plants for which genomes show potential as bioenergy crops,
• In identifying genes for desirable bioenergy traits,
• In screening and selecting superior bioenergy genotypes, and
• In supporting efforts to modify plant genomes, making them better bioenergy crops.
2.3 evolutIonary relatIonshIPs In hIGher
Plants and theIr Genomes
Evolutionary or phylogenetic approaches (Henry 2005) can be applied to the search for suitable
species or traits for bioenergy production. The composition of a given plant's biomass is a major
determinant of the suitability of that plant for use in specific bioenergy production processes. Cell
wall composition is a major factor, and this varies by plant group. A molecular phylogenetic approach
will ultimately allow the plants with the appropriate sets of genes for the desired composition to
be found efficiently.
2.4 Genome sequencInG
The last few years have seen the emergence of radically improved technology for DNA sequencing
(Schuste 2008), making large-scale plant genome analysis much more feasible. Genome sequencing
of potential bioenergy crop plants provides a platform for analysis of the genetic potential of these
species and targets for their genetic improvement.
The sequence of the sorghum genome (Paterson et al. 2009) provides a reference genome for not
only sorghum but also the many closely related grass species that are potential bioenergy crops (e.g.,
sugarcane and
Miscanthus
). Despite the polyploidy complexity of the sugarcane genome, significant
efforts are now being made to obtain a reference genomic sequence for this species because of
