Improving sugarcane for biofuel: engineering for an even better feedstock

Abstract

Sugarcane is a proven biofuel feedstock and accounts for about 40% of the biofuel production worldwide. It has a more favorable energy input/output ratio than that of corn, the other major biofuel feedstock. The rich resource of genetic diversity and the plasticity of autopolyploid genomes offer a wealth of opportunities for the application of genomics and technologies to address fundamental questions in sugarcane towards maximizing biomass production. In a workshop on sugarcane engineering held at Rutgers University, we identified research areas and emerging technologies that could have significant impact on sugarcane improvement. Traditional plant physiological studies and standardized phenotypic characterization of sugarcane are essential for dissecting the developmental processes and patterns of gene expression in this complex polyploid species. Breeder friendly DNA markers associated with target traits will enhance selection efficiency and shorten the long breeding cycles. Integration of cold tolerance from Saccharum spontaneum and Miscanthus has the potential to expand the geographical range of sugarcane production from tropical and subtropical regions to temperate zones. The Flex-stock and mix-stock concepts could be solutions for sustaining local biorefineries where no single biofuel feedstock could provide consistent year-round supplies. The ever increasing capacities of genomics and biotechnologies pave the way for fully exploring these potentials to optimize sugarcane for biofuel production. It is inevitable that fossil fuel will be replaced by renewable biofuels and other alternative energy sources. Global demand for biofuel as a clean renewable energy source is rising rapidly. By 2017, the US alone will need 135 billion liters of renewable fuels as a goal set by the 20 in 10 program (reduce gasoline usage by 20% in 10 years) in 2007. The current total global production of renewable fuels is 50 billion liters a year, about 40% of which comes from sugarcane that is mostly produced by Brazil. Recent investments from public and the private sectors worldwide in biofuel research have brought sugarcane (Saccharum spp.) to the forefront as the most productive first generation energy crop. However, there Correspondence: Eric Lam,

Analysis of genes controlling biomass traits in the genome of sugarcane (Saccharum spp. hybrids)

“…Miscanthus to a tropical climate and expands sugarcane production to temperate, dry and cold conditions (Alexander, 1985, Burner et al, 2009, Lam et al, 2009. Recently, the use of molecular markers in the sugarcane breeding program (marker-assisted selection) has allowed the direct comparison of DNA genetic diversity and provides a precise tool in assessing the genetic diversity of the germplasm (Tabasum et al, 2010, Berkman et al, 2012.…”

“…This is considered to be advantageous relative to the first generation of biofuels, as they have a higher energy production potential, lower production cost, sustainable CO 2 balance, no competition with the food production and have a wide range of plant biomass sources which are available at costs affordable to a biorefinery (Yuan et al, 2008, Henry, 2010a. As of 2009, sugarcane biomass as sucrose accounted for about 40% of the biofuels feedstock worldwide for first generation biofuel production (Lam et al, 2009). Using sugarcane bagasse as a feedstock for second generation biofuels would lead to a doubling the current output of biofuel production from sugarcane (Halling and SimmsBorre, 2008).…”

“…Unexploited genes not only from the Saccharum germplasm, but also in other related species, such as cold tolerant genes in S. spontaneum and Miscanthus, or drought tolerant genes in sorghum, once identified would allow their integration into the sugarcane genome, facilitating the production of more sugarcane biomass in temperate areas or under dry conditions (Lam et al, 2009). .…”

“…Recently, the use of molecular markers in the sugarcane breeding program (marker-assisted selection) has allowed the direct comparison of DNA genetic diversity and provides a precise tool in assessing the genetic diversity of the germplasm (Tabasum et al, 2010, Berkman et al, 2012. The use of markers associated with the desired traits in combinations with the advances in Next Generation Sequencing (NGS) technology, bioinformatics tools and high-throughput phenotyping methods, will significantly improve the sugarcane breeding programs (Lam et al, 2009). NGS will allow a large number of markers, such as SNPs, to be generated, which could be used to obtain a high density of markers with high coverage across the genome, to allow the dissection of the important traits they associate with.…”

“…High-throughput phenotyping methods will collect data from a large number of samples to overcome the small effects of genes, especially the QTL controlling the traits (Lam et al, 2009). …”