Sugar Beet, Energy Beet, and Industrial Beet - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 82

including as a biofuel feedstock or for production of other industrial chemicals
[ 5 - 7 ]. Indeed, much of the recent historical work of beet breeding has been toward
improving crop protection traits. Varieties continue to improve incrementally for
sucrose yield and content, and projected sucrose needs may be satisfied for the
foreseeable future with the same number, or fewer, hectares of sugar beets as are
currently grown.
Sucrose is perhaps the most abundant, chemically pure, renewable resource
available, and numerous chemical transformations of sucrose have been described
[ 8 , 9 ]. Conversion of sucrose to ethanol is an ancient and simple biochemical
transformation (via fermentation with yeast), and chemical transformations of etha-
nol also lead to useful industrial compounds. Modification of sucrose itself has
non-caloric sweetener value (the artificial sweetener sucralose is an example), and
its fatty acid derivatives can be used for coatings and polymers of various types. The
breeding targets to increase the yields of these specialty products remain the same as
for increasing sucrose yield per hectare. The sugar industry continues to look into
alternative products, such as energy beet and beets for other industrial uses, for their
long-term sustainability. Sugar beet germplasm and breeding methods will have a
primary role in creating new beet crops to satisfy industry needs.
Beets solely intended for energy production were conceived during the first US
oil shortage in the 1970s when sugar beet breeders recognized the potential for
converting sucrose to ethanol for use as a liquid transportation fuel [ 10 , 11 ]. These
research activities declined when oil prices stabilized. Over the past 10 years,
interest in beets for energy production has rebounded, with increasing petroleum
prices and the restructuring of the EU sugar industry converging to improve the
economic climate for biofuels and other industrial feedstocks derived from beets
[ 12 , 13 ]. Real and potential uses for sugar beets are quite diverse, in addition to
sugar beet's primary use as a source of sweetener in human diets. Coproducts such
as pulp (the insoluble root tissue after sucrose extraction) and molasses (the liquid
remaining after sucrose refining) are used as animal feed or as feedstocks for the
manufacture of specialty chemicals.
Taxonomy and Domestication
Beets ( Beta vulgaris spp. vulgaris L.) are dicots in the family Amaranthaceae
(formerly Chenopodiaceae) in the order Caryophyllales. Beets are classified by
crop type (sugar, fodder, leaf, or table). The wild sea beet ( Beta vulgaris spp.
maritima ), often found within a few meters of mean sea level, is considered the
ancestor of the crop types [ 14 , 15 ]. All types are outcrossing, wind pollinated, and
cross compatible. Wild beets are indigenous to the Mediterranean coastal area, from
the Cape Verde Islands in the west and south along Moroccan coast, east through
the Middle East to India, and north along the Atlantic coast to the UK and
Scandinavia [ 14 ]. As a group, Caryophyllales are often found in marginal and
stressful environments.