Genome sequencing to aid sorghum research

By Susanne Retka Schill | March 05, 2009
Plant breeders looking toward sorghum as a next-generation ethanol feedstock have new insight into the genetics of the drought-tolerant plant following the publication of the sorghum genome by the U.S. DOE Joint Genome Institute and several partner institutions.

"This is an important step on the road to the development of cost-effective biofuels made from nonfood plant fiber," said Anna Palmisano, DOE associate director of science for biological and environmental research. "Sorghum is an excellent candidate for biofuels production with its ability to withstand drought and prosper on more marginal land. The fully sequenced genome will be an indispensable tool for researchers seeking to develop plant variants that maximize these benefits."

The comparative analysis of the sorghum genome appeared in the Jan. 29 edition of the journal Nature. "Sorghum will serve as a template genome to which the code of other important biofuel feedstock grass genomes—switchgrass, miscanthus and sugarcane—will be compared," said Andrew Paterson, the article's lead author and director of the Plant Genome Mapping Laboratory at the University of Georgia.

Prized for its drought resistance and high productivity, sorghum is currently the second most prevalent biofuels crop in the United States behind corn. Grain sorghum produces the same amount of ethanol per bushel as corn with one-third less water needed for crop production. In addition to working to improve grain sorghum (also known as milo), researchers are developing sweet sorghum and high-biomass sorghum as feedstocks for advanced biofuels. Biomass sorghum varieties based on forage sorghums grow up to 18 feet tall with yields up to 20 tons per acre. Sweet sorghum varieties have long been grown for the sugary syrup extracted from the stems. Historically, sweet sorghum production has been limited by narrow markets for the syrup and the variety's low seed production rates. Researchers are focusing on improving sweet sorghum's seed production while enhancing sugar yields. Annual sweet sorghum crops could potentially extend the processing season in areas where sugarcane is grown.

Scientists and industry officials said completion of the sorghum genome mapping will aid with the sequencing of numerous other potential bioenergy crops. Sorghum is only the second grass genome to be completely sequenced to date, following rice. The data being generated from plant genome sequencing helps crop breeders hone in on agronomic traits such as rapid growth, drought resistance and pest tolerance. Biofuels researchers are developing strategies to optimize the plants themselves as biofuels feedstocks, altering characteristics such as branching habit, stem thickness and cell wall chemistry. Genome sequencing has also aided work in microbial biomass breakdown, including the manipulation of fungi, bacteria and yeast organisms targeted for cellulosic ethanol and biobased chemical production.