Comprehensive Approach to Improve Biofuel Feedstocks using Rice as a Model System

Developing sustainable energy production from cellulosic feedstock requires a comprehensive approach to maximize plant biomass production. Our approach includes three studies in the model system rice (Oryza sativa): (1) physiological characterization of biomass traits, (2) screening of rice mutant for enhanced biomass output and (3) cell-wall composition analysis to enhance downstream processing for bioenergy. We identified a negative correlation between total biomass and photosynthetic rates in rice. Total biomass yield was negatively correlated with chlorophyll content, night-time stomatal conductance, transpiration, and dark respiration. For the mutant study, 12,000 mutants were screened for increased biomass relative to the parent variety. One mutant was identified that showed a 2-fold increase in biomass under both field and greenhouse conditions, and had increased height, tiller number, tiller length, seed weight, girth and  photosynthetic rate relative to the parent variety. To identify rice lines that vary in cell-wall composition, we are combining traditional analytical methods (detergent and dietary fiber analyses) and near-infrared reflectance spectroscopy (NIRS) to develop a NIRS-based rapid screening method for rice. We advanced a large (>1,700 lines) recombinant inbred line (RIL) F₆ population developed from a cross of two parents with distinct biomass and cell-wall phenotypes (Aswina x IR64) to provide resources for large-scale phenotyping and rapid identification of target QTL regions. Information on the loci and biological systems underlying the functional variation in rice will be translated to switchgrass for improvement of biomass traits.