Sunday, April 29, 2007 - 1:55 PM

Cell wall composition and accessibility to hydrolytic enzymes is differentially altered in divergently bred switchgrass (Panicum virgatum L.) genotypes

G. Sarath1, Danny E. Akin2, K.P. Vogel1, and R.B. Mitchell1. (1) Grain, Forage, and Bioenergy Research Unit, USDA-ARS, 344 Keim Hall, UN-L East Campus, Lincoln, NE 68583-0937, (2) Russell Research Center, Quality Assessment Research Unit, ARS-USDA, 950 College Station Road, Athens, GA 30605

Switchgrass plants from two populations, C+3 developed by three breeding generations for high digestibility and C-1 developed by one generation of breeding for low digestibility, were used in this study  Above ground biomass from 12 selected genotypes, 3 each with high or low digestibility within each population were analyzed for their cell wall aromatics and polysaccharides.  The ratio of p-coumaric acid:ferulic acid  was greater (P≤ 0.05) for the high-lignin C-1 population over the low-lignin C+3 population, although the amounts of these two phenolics did not differ between populations.  Combined values of guaiacyl + syringyl-lignin were consistently higher in genotypes from the C-1 population as compared to the genotypes from the C+3 population. Overall, p-coumaric acid was released by enzymes in greater amounts than ferulic acid in all these genotypes. Genotypes in the C-1 population exhibited lower dry weight loss as compared to the genotypes in the C+3 population after enzymatic digestion, suggesting changes in cell wall architecture.  Overall our data highlight the phenotypic plasticity coded by the switchgrass genome and suggest that combining DMD with other more specific cell-wall traits could result in genotypes with greater utility as bioenergy feedstocks.