Biology Reference
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harvest. Sugarcane combines a high polyploidy,
a heterozygous genome, and C4 photosynthetic
metabolism, making it one of the most efficient
converters of light into chemical energy. Sug-
arcane is an important cash crop in tropical and
subtropical areas and is grown in about 100
countries (FAOSTAT 2012). It is mainly grown
for the production of sucrose, which accumulates
at high concentrations in the stem, and the very
high productivity of this crop makes it one of the
most economically attractive crops for the pro-
duction of energy from biomass (Waclawovsky
et al. 2010). Apart from sucrose, many by- or co-
products (bagasse, molasses, bioethanol, mud)
used for a wide range of industrial applications
(livestock feed, energy or paper production,
bio-fertilization, bio-refinery, particleboard,
etc.) can also be obtained from sugarcane. In
2010, more than 23 million hectares of sugar-
cane were harvested worldwide, ranking only
12
th
in crop harvested area, far behind wheat
(217 million hectares), maize (161 million
hectares), and rice (153 million hectares).
However sugarcane was by far the most har-
vested and processed product in the world,
with 1.7 billion tons of cane harvested and
more than 133.6 million tons of sucrose and
54 million tons of molasses produced (FAO-
STAT 2012). Sugarcane is the main source
of sucrose worldwide, representing more than
75% of world production. After maize, it is the
second largest source of sugar-based bioethanol
(first generation bioethanol), with more than
26 billion liters produced. Bioethanol is mainly
produced in Brazil where more than half the
area under cane is dedicated to it (Dal-Bianco
et al. 2011). In Brazil, sugar-based ethanol
and bagasse-based electricity produced from
sugarcane together represent 17% of national
energy consumption, which makes sugarcane
one of the main sources of renewable energy
and one of the main alternatives to fossil
fuel (Brazilian Ministerio de Minas e Energia
2011; Matsuoka et al. 2009). Leaving aside the
controversy about the social and environmental
costs of converting land to grow biofuel crops
(De Araujo and Moura 2011; Duailibe 2010;
Walker 2009), sugarcane is arguably one of the
best crops for biofuel production in terms of
net energy value (NEV), when considering all
resource inputs (Garoma et al. 2011). Moreover,
NEV is expected to increase with the develop-
ment of cellulosic ethanol (second-generation
bioethanol) (Dias et al. 2011a; Dias et al.
2011b), since the lignocellulosic fraction of
sugarcane is estimated to represent 50% of its
energy potential (Botha 2009; Manners 2011).
In favorable agro-climatic zones, sugarcane
fresh biomass frequently exceeds 100 tons of
cane/ha/year using ordinary fertilization input
levels. This outstanding biomass production,
combined with the development of cellulosic
ethanol and genetic transformation technolo-
gies, means sugarcane will play a major role
among industrial plants in meeting the demand
for sugar, renewable energy, and bio-products
(Figure 13.1) (Arruda 2011).
Currently increased yield is the main objec-
tive of sugarcane genetic improvement. Until
now, sucrose yield per unit area was the main
goal of sugarcane breeders since this parameter
is the most closely correlated with both farmers'
and industrial incomes (Jackson 2005). However
breeding either for both sucrose and biomass
or for only biomass, as already suggested by
Alexander (1985), is clearly one of the new rea-
sons for cultivating sugarcane, given the urgent
need to reduce the consumption of fossil fuels.
Depending on industrial applications, breeding
objectives can be summarized in three sugar-
cane ideotypes: the traditional “sugar” ideotype
bred for sugar (
12% fiber); the
“energy cane type I,” bred for both sugar (
∼
13% sugar,
∼
∼
13%)
and fiber (
17%); and the “energy cane type II,”
bred only for fiber (
∼
30% fiber) pro-
duction (Tew and Cobill 2008). Sugarcane yield
depends on two key components: the quantity of
biomass and the quality of the dry matter (DM).
The quantity of cane biomass depends on agro-
morphological traits related to plant architec-
ture (tillering, stalk height, and diameter), which
are usually significantly genetically correlated
∼
5% sugar,
∼
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