Breeding of Sugarcane - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 34

Major Breeding Achievements
Currently, the breeding of sugarcane varieties aims to obtain, through the selection
of clones that have high productivity and high sucrose per hectare, more rustic, as
drought tolerance, resistance to pests and diseases and better adaptation to mechan-
ical harvesting [ 15 ].
Within the programs for genetic improvement of sugarcane, conventional breed-
ing today is still the main route for obtaining improved varieties. Over the years of
cultivation of sugarcane, problems with diseases were solved with the introduction
of resistant varieties. Sugarcane clones are tested to establish reaction to the main
diseases such as smut, mosaic, leaf scald, rust, and ratoon stunting. Currently,
ratoon stunting can be controlled with thermal treatment and by disinfecting
instruments used in the cutting of the sugarcane.
One of the great advancements of conventional improvement was the develop-
ment of clones resistant to ratoon stunting and smut. At present, 216 diseases were
identified in sugarcane. Among these, ten can be considered to have great economic
importance. The most important diseases are controlled with the use of resistant
varieties; through crossings (hybridization), breeders incorporate genetic resistance
in the new varieties of developed canes. It is worthwhile to mention that currently
no control measure similar to other crops, like regular application of fungicides and
bactericides, is made on sugarcane.
The production of sugarcane has been increasing globally due to the develop-
ment of improved varieties adapted to their regions of cultivation. The genetic
improvement programs are fundamental, because they accumulate alleles of agro-
nomic interest within the set of genes submitted to successive selection processes.
In the last 50 years, cane improvement was highly influenced by the improvement
of machines and equipment, technological progress, precision agriculture, and new
market requirements that influence selection of new varieties showing that the
present cane is an integrated package that offers benefits to the sugar and alcohol
industries. Over the last 30 years, breakthroughs in genetics, especially in molecular
genetics, also happened.
Over the last two decades, the improvement programs have dedicated part of
their studies and investments in the area of biotechnology [ 16 ]. The utilization of a
series of biotechnological tools for genetic analysis had the main objective to
expand the existing knowledge as well as clarify the structure and the complex
behavior of the cane genome, one example of these studies was SUCEST (the
Sugarcane EST Project) [ 17 ] which identified 43,000 genes. Starting from the
project, the researchers aimed to exchange information with researchers involved
in saccharose metabolism. Seven genes were identified responsible for transporting
sugars and are more active in stem sections closer to the root where more sugar
accumulates. The advancement of biotechnology for sugarcane consists in creating
transgenic plants with the identified genes.
Future breeding objectives include the development of highly productive sug-
arcane, with high saccharose content, drought tolerance, and high production of