Breeding of Sugarcane - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 39

interest for the production and use of biofuels, several multinational companies that
have commercial transgenic events in other crops (soy and corn for example)
started to invest in research with transgenic cane, which increases the chance of a
commercial release in the next years.

Seed Production

Sugarcane is an allogamous species following a sexual mode of reproduction; but,
when cultivated commercially, it is multiplied asexually by vegetative propagation
[ 37 ]. In cane production, the seeds are important in genetic improvement programs
and those with high genetic quality are sought [ 15 ].
For the production of seeds, sugarcane needs specific environmental conditions
so that flowering can be induced. The flowering of cane is a complex physiological
process formed by several stages of development. Each stage has its own environ-
mental and physiological needs. Factors that influence the induction of cane
flowering include photoperiod (12-012.5 h of light), temperature (18-32 C),
thermal amplitude ( 13 C), latitude (between 10 N and 10 S), and humidity

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( 60 %), among others [ 38 ]. Outside of these conditions, or under adverse condi-

tions, flowering occurs, but often synchrony between male and female lines remains
a challenge; therefore, strategies such as sowing at different dates and photoinduc-
tive treatments are needed to aid crossbreeding.
In sugarcane breeding programs, the production of seeds is done using basically
two types of crossings: biparental and multiple. In biparental crosses, hybridization
is done between two genotypes of interest, while in the multiple crosses, only the
identity of the mother plant is of interest, the pollen coming freely from diverse
individuals [ 39 ]. The production of seeds with high physiological potential repre-
sents the basis for a good genetic improvement program. However, once a crop
variety is selected and released, production of seeds is not ideal, because flowering
is suppressed to avoid reducing the productive potential of the cane [ 40 ].

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Market Challenges

In spite of the successive economic crises that the world is going through, the
demand for products of sugarcane is rising and consistent. The world demand for
energy is projected to grow by 4.5 % per year and ethanol has been identified as an
important source for meeting this demand. Attached to this, two economic phe-
nomena pose potential challenges - the insertion into the market of billions of new
consumers in developing countries and the implementation of programs that seek
substitution of fossil fuels by renewable fuels in different countries of the world. To
exemplify, the United States in the next 10 years intends to increase the use of
ethanol mixed with gasoline. Put into practice, this will result in the United States