Southerners may best know sorghum as sweet, biscuit-topping syrup. But the small grain's uses range from a dependable, drought-tolerant food crop to biofuel source, says a University of Georgia researcher who led a team that recently sequenced the plant's genome.
"Sorghum's importance is enormous," said Andrew Paterson, a distinguished research professor and director of the Plant Genome Mapping Laboratory, a joint unit of the UGA College of Agricultural and Environmental Sciences and Franklin College of Arts and Sciences.
Paterson and his collaborators, from as close as South Carolina and as far away as India, Pakistan and Germany, mapped and analysed the genome of Sorghum bicolor, placing 98 per cent of its genes in their chromosomal context. At 730 million bases, or letters of DNA, sorghum has a genetic code a quarter the size of the human genome.
The results of the study appear in the January 2009 issue of international science journal Nature.
Drought tolerance makes sorghum important in dry regions like northeast Africa and the US southern plains. It needs only half the water it takes to grow corn.
"Not nearly as much has been invested in sorghum as in corn," Paterson said. "According to the United Nations Food and Agriculture Organisation, sorghum yields increased less than one per cent per year over the last 45 years, only about half the rate of corn, rice and wheat yields. Something is wrong with this picture. If new information and tools from the sequencing change that, it'll improve millions of people's lives."
The sorghum that Paterson studied is drought tolerant, but its wild cousins can survive on even less water and resist more diseases and pests. Breeders can use the sequence as a tool to blend desirable traits into more improved commercial plants.
The sequenced sorghum genome is also being used to improve biofuel crops like sugarcane and Miscanthus, a genus of 15 species of perennial grasses that is a leading biofuel crop in Europe. These plants have much larger and more complicated genomes than sorghum, a close relative that can be a guide to accelerating their improvement.
In the US now, it's not clear whether Miscanthus or switchgrass will dominate the biofuel arena, he said, but recent side-by-side studies show that Miscanthus out yields switchgrass by as much as three to one.
Sorghum is also used to make biofuel and currently is the second largest source of fuel ethanol in the US. Corn is first. There is a shift taking place away from seed-based biofuel produced today to cellulose-based production, a process for which sorghum also shows great promise. That is why the US Department of Energy's Joint Genome Institute got involved with sorghum sequencing.
