Brown midrib sorghum for second-generation ethanol production. Abstract

Abstract

Sorghum[Sorghum bicolor (L.) Moench] stover can provide an abundant alternative source of fermentable sugars through enzymatic hydrolysis (Vermerris et al., 2007). While production of cellulosic ethanol from stover is feasible from an energy-balance perspective, its production is currently not economically viable. Improvements in bio-processing, technologies coupled with development of high biomass yielding genotypes with low lignin content make ethanol production cost effective. The brown midrib (bmr) mutant sorghum lines have significantly lower levels of lignin content (51% less in stems and 25% less in leaves (Porter et al., 1978). Therefore, the use of bmr cultivars would reduce the cost of biomass-based ethanol production by reducing pre-processing costs. ICRISAT has developed 11 female parents (A-/B- lines) and 22 pollen parents (R-lines) using bmr 1, bmr 3 and bmr 7 sources for development of high biomass bmr sorghum hybrids (Reddy et al., 2008). Preliminary evaluation of bmr hybrid parents (4 R-lines) derived from bmr 1 source (IS 21887) indicated 20% lower lignin content on whole plant basis compared to source (4.24%). Further, two brown midrib sources bmr 6 (reduced activity of cinnamyl alcohol dehydrogenase) and bmr 12 (reduced activity of caffeic acid O-methyl transferase) are under use in breeding program for bmr introgression. With several bmr mutant sources available in gene bank, ICRISAT has a comparative advantage to develop high biomassyielding bmr sorghum hybrids for enhancing ethanol production from stover.