Domestication of cereal crops has provided a stable source of food for thousands of years. The extent to which lignocellulosic crops will contribute to the world's renewable energy depends largely on how the new crops will be domesticated. Growing miscanthus as biofuel feedstocks on marginal and degraded land in northern and northwestern China offers an example for developing theoretical framework and practical strategies for energy crop domestication. The domestication should incorporate the highest possible genetic diversity from wild species, focus on the improvement of drought and cold tolerance especially in the stage of crop establishment, increase the efficiencies of water and nutrient uses and photosynthesis, adjust vegetative growing season according to local temperature and precipitation, and reduce or prevent seed production. Positive ecological effects on soil conservation, landscape restoration, carbon sequestration, and hydrological cycles should be maximized, while negative impact on biodiversity needs to be minimized. With the development of other sources of renewable energy, the role of lignocellulosic crops may evolve from primarily energy production to increasingly ecological restoration and biomaterial development. The integration of this new cropping system into the existing agriculture may open a new avenue to the long-term sustainability of our society.

Sang T (2011) Toward the domestication of lignocellulosic energy crops: Learning from food crop domestication. J. Integr. Plant Biol. 53(2), 96–104.

Bioenergy crops currently provide the only source of alternative energy with the potential to reduce the use of fossil transportation fuels in a way that is compatible with existing engine technology, including in developing countries. Even though bioenergy research is currently receiving considerable attention, many of the concepts are not new, but rather build on intense research efforts from 30 years ago. A major difference with that era is the availability of genomics tools that have the potential to accelerate crop improvement significantly. This review is focused on maize, sorghum and sugarcane as representatives of bioenergy grasses that produce sugar and/or lignocellulosic biomass. Examples of how genetic mapping, forward and reverse genetics, high-throughput expression profiling and comparative genomics can be used to unravel and improve bioenergy traits will be presented.

Vermerris W (2011) Survey of genomics approaches to improve bioenergy traits in maize, sorghum and sugarcane. J. Integr. Plant Biol. 53(2),105–119.

The main feedstocks for bioethanol are sugarcane (Saccharum officinarum) and maize (Zea mays), both of which are C₄ grasses, highly efficient at converting solar energy into chemical energy, and both are food crops. As the systems for lignocellulosic bioethanol production become more efficient and cost effective, plant biomass from any source may be used as a feedstock for bioethanol production. Thus, a move away from using food plants to make fuel is possible, and sources of biomass such as wood from forestry and plant waste from cropping may be used. However, the bioethanol industry will need a continuous and reliable supply of biomass that can be produced at a low cost and with minimal use of water, fertilizer and arable land. As many C₄ plants have high light, water and nitrogen use efficiency, as compared with C₃ species, they are ideal as feedstock crops. We consider the productivity and resource use of a number of candidate plant species, and discuss biomass ‘quality’, that is, the composition of the plant cell wall.

Byrt CS, Grof CPL, Furbank RT (2010) C₄ plants as biofuel feedstocks: Optimising biomass production and feedstock quality from a lignocellulosic perspective. J. Integr. Plant Biol. 53(2), 120–135.

Rice is a model organism for studying the mechanism of cell wall biosynthesis and remolding in Gramineae. Mechanical strength is an important agronomy trait of rice (Oryza sativa L.) plants that affects crop lodging and grain yield. As a prominent physical property of cell walls, mechanical strength reflects upon the structure of different wall polymers and how they interact. Studies on the mechanisms that regulate the mechanical strength therefore consequently results in uncovering the genes functioning in cell wall biosynthesis and remodeling. Our group focuses on the study of isolation of brittle culm (bc) mutants and characterization of their corresponding genes. To date, several bc mutants have been reported. The identified genes have covered several pathways of cell wall biosynthesis, revealing many secrets of monocot cell wall biosynthesis. Here, we review the progress achieved in this research field and also highlight the perspectives in expectancy. All of those lend new insights into mechanisms of cell wall formation and are helpful for harnessing the waste rice straws for biofuel production.

Zhang B, Zhou Y (2011) Rice brittleness mutants: a way to open the ‘black box’ of monocot cell wall biosynthesis. J. Integr. Plant Biol. 53(2),136–142.

Biomass utilization is increasingly considered as a practical way for sustainable energy supply and long-term environment care around the world. In concerns with food security in China, starch or sugar-based bioethanol and edible-oil-derived biodiesel are harshly restricted for large scale production. However, conversion of lignocellulosic residues from food crops is a potential alternative. Because of its recalcitrance, current biomass process is unacceptably expensive, but genetic breeding of energy crops is a promising solution. To meet the need, energy crops are defined with a high yield for both food and biofuel purposes. In this review, main grasses (rice, wheat, maize, sorghum and miscanthus) are evaluated for high biomass production, the principles are discussed on modification of plant cell walls that lead to efficient biomass degradation and conversion, and the related biotechnologies are proposed in terms of energy crop selection.

Xie G, Peng L (2011) Genetic engineering of energy crops: A strategy for biofuel production in China. J. Integr. Plant Biol. 53(2), 143–150.

Willows (Salix spp.) are a very diverse group of catkin-bearing trees and shrubs that are widely distributed across temperate regions of the globe. Some species respond well to being grown in short rotation coppice (SRC) cycles, which are much shorter than conventional forestry. Coppicing reinvigorates growth and the biomass rapidly accumulated can be used as a source of renewable carbon for bioenergy and biofuels. As SRC willows re-distribute nutrients during the perennial cycle they require only minimal nitrogen fertilizer for growth. This results in fuel chains with potentially high greenhouse gas reductions. To exploit their potential for renewable energy, willows need to be kept free of pests and diseases and yields need to be improved without significantly increasing the requirements for fertilizers and water. The biomass composition needs to be optimized for different end-uses. Yields also need to be sustainable on land less productive for food crops to reduce conflicts over land use. Advances in understanding the physiology and growth of willow, and in the identification of genes underlying key traits, are now at the stage where they can start to be used in breeding programs to help achieve these goals.

Karp A, Hanley SJ, Trybush SO, Macalpine W, Pei M, Shield I (2011) Genetic improvement of willow for bioenergy and biofuels. J. Integr. Plant Biol. 53(2), 151–165.

Rapid determination of the properties of lignocellulosic material is highly desirable for biomass production and utilization. In the present study, measurements of woody biomass digestibility and chemical composition using near-infrared reflectance (NIR) spectroscopy were calibrated. Poplar and eucalyptus materials were recorded in NIR spectrum as well as determined for their chemical compositions of Klason lignin, α-cellulose, holocellulose, lignin syringyl/guaiacyl (S/G) ratio and enzymatic digestibility. Fitting of the NIR information with chemical properties and digestibility by partial least-squares (PLS) regression generated a group of trained NIR models that were able to be used for rapid biomass measurement. Applying the models for woody biomass measurements led to a reliable evaluation of the chemical composition and digestibility, suggesting the feasibility of using NIR spectroscopy in the rapid characterization of biomass properties.

Hou S, Li L (2011) Rapid characterization of woody biomass digestibility and chemical composition using near-infrared spectroscopy. J. Integr. Plant Biol. 53(2), 166–175.