Breeding of Sugarcane - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 36

paralyzation of the development of the flowered stems, causing reduction of
productivity.
8. Erect growing habit : This trait is important for mechanization as well as the
manual harvest.
9. Easy or natural straw down : This will help the harvester in the stem cleaning
operation and generate less vegetal impurities.
10. Sprouting : The yield of the stalks of sugarcane decreases each cut. In breeding
programs and also commercial areas, it is desirable that cultivars show high
ability to sprout after cutting.
Besides these characteristics, others include adaptability and stability, stem
height (directly related to productivity), and tolerance to non-biotic stresses like
cold and heat. The selection and commercialization process of a new variety is long,
on the average about 10-13 years. In this time span, new technologies can be used
to maximize the efficiency of the breeders work and reduce the time to develop a
new sugarcane variety with favorable characteristics.
Breeding Strategies and Integration of New Biotechnologies
Gene discovery and genomics are essential tools for the future of sugarcane
improvement. Sequencing of sugarcane expressed sequenced tags (ESTs) greatly
contributed to gene discovery process, e.g., Sugarcane EST Project (SUCEST)
initiative [ 23 ]. Currently, the information from the SUCEST, the Sugarcane Gene
Index (SGI), gene expression data, and records of the agronomic, physiological, and
biochemical characteristics of sugarcane cultivars are all integrated in SUCEST-
FUN database ( http://sucest-fun.org ) [ 17 ]. Many large-scale array-based studies of
gene expression have been performed in sugarcane in the past decade. Gene
expression studies have been conducted using a variety of platform array technol-
ogies including cDNA macroarrays using nylon membranes, cDNA microarrays
spotted onto glass slides, and oligonucleotide microarrays either spotted or synthe-
sized in situ. In some instances, gene expression profiling using arrays has been
used to identify genes specific to a tissue (e.g., stems, leaves, roots) related to
various traits such as sucrose content, cell wall synthesis, and cold and drought
response [ 24 , 25 ].
The transcriptome projects have contributed to advances in the understanding of
gene regulation system of sugarcane. However, there are still gaps in key informa-
tion as variation among different copies of the same gene in the same individual and
discovery of promoter sequences. The genome of commercial sugarcane is esti-
mated to be approximately 10Gb [ 26 ], but the polyploidy nature of sugarcane
complicates genome sequence assembly into contiguous hom(oe)ologous chromo-
somal sequences [ 27 ]. Thus, obtaining the reference assembled monoploidy
genome for sugarcane is a critical step to solve such issues. Importantly, an
international consortium, SUGESI ( http://sugarcanegenome.org ) , has been formed