01/01/2011
Diversity Among Rice Varieties Indicates Multiple Targets for Biomass Improvement
The Science
Breeding cellulosic feedstock crops with enough biomass for sustainable liquid fuel production is a major challenge. We can exploit natural variation in bioenergy-relevant traits, but many of the most promising feedstock crops, such as perennial grasses, have large genomes and limited genetic resources, making breeding for such traits difficult. However, such tools are readily available for rice, a well-studied crop plant that shares many developmental and physiological processes as well as gene content with other grasses. These shared characteristics make rice useful as a model for modifying other newly emerging bioenergy crops. Researchers at Colorado State University, in collaboration with the International Rice Research Institute (IRRI) in the Philippines, assessed variation in traits such as biomass, height, tiller number, plant girth, cell-wall composition, and water-use efficiency among a diverse set of 20 rice varieties at different stages of development. Significant variation was found for all traits, and this variation was determined to be heritable. Additionally, high yields exhibited by different varieties were achieved through different combinations of traits, indicating the contribution of multiple genetic loci to overall biomass productivity and suggesting that multiple targets can be utilized in traditional breeding programs to develop other energy feedstocks with enhanced yield.
The Impact
Although heritability estimates were significant for all traits, heritabilities were higher in traits relating to plant size and architecture than for physiological traits. Trait variation was largely explained by variety and breeding history (advanced versus landrace) but not by varietal groupings (indica, japonica, and aus). In the context of cellulosic biofuels development, cell wall composition varied significantly among varieties. Surprisingly, photosynthetic rates among the varieties were inversely correlated with biomass accumulation. Examining these data in an evolutionary context reveals that rice varieties have achieved high biomass production via independent developmental and physiological pathways, suggesting that there are multiple targets for biomass improvement. Future efforts to identify loci and networks underlying this functional variation will facilitate the improvement of biomass traits in other grasses being developed as energy crops.
Principal Investigator
Jan E. Leach
Colorado State University
BER Program Manager
Kari Perez
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]
References
Jahn, C. E., J. Mckay, R. Mauleon, J. Stephens, K. L. McNally, D. R. Bush, H. Leung, and J. E. Leach. 2011. “Genetic Variation in Biomass Traits Among 20 Diverse Rice Varieties,” Plant Physiology 155, 157–68. DOI:10.1104/pp.110.165654.