Sunday, April 29, 2007

Genetic enhancement of sorghum for biofuel production

Ana Saballos1, Gebisa Ejeta1, and Wilfred Vermerris2. (1) Agronomy, Purdue University, 915 W. State Street, West Lafayette, IN 47907, (2) Agronomy, University of Florida Genetics Institute, PO Box 103610, 1376 Mowry Road, Gainesville, FL 32610-3610

Genetic improvement of biomass crops can significantly reduce the overall cost of biomass-to-ethanol conversion. Major traits affecting biomass utility are lignin content and composition, soluble carbohydrate content and biomass yield. Sorghum offers advantages that make it an attractive biomass crop. It is tolerant to drought, performs well on marginal lands, and possesses a deep root system that helps prevent the loss of soil organic matter. We are working towards improving the quality of sorghum as a feedstock by combining traits from useful germplasm sources of brown midrib (bmr) mutants, sweet sorghums, and high biomass producers. The genetic basis of these characteristics is poorly understood. Therefore, we have developed a population of recombinant-inbred lines from crosses between a sweet sorghum and a bmr mutant.  Characterization of this population will allow identification of QTL associated with biomass yield, cell wall composition and soluble sugar content.  Based on the chemical composition of the mutants’ cell wall and mapping data from this population we have successfully identified the gene underlying the bmr6 mutation. Through a combination of genetic and chemical approaches we have established the number of independent bmr loci associated with our collection of bmr mutants. We are currently studying the effect of pyramiding the non-allelic bmr genes on plant fitness and cell wall composition.  Sugar concentration in stalks from this population was evaluated to determine the inheritance of the sweet sorghum trait. Molecular markers resulting from these experiments will facilitate the combination of these traits to develop improved lines for biofuel production.