Climate change poses a major challenge to humanity's ability to feed its growing population. But a new study of sorghum, led by Stephen Kresovich and Geoff Morris of the University of South Carolina, promises to make this crop an invaluable asset in facing that challenge. Just published in the Proceedings of the National Academy of Sciences (PNAS), the paper puts genetic tools into the hands of scientists and plant breeders to help accelerate their ability to adapt sorghum to new conditions.
A hardy cereal crop that was first domesticated in the Horn of Africa some 10,000 years ago, sorghum is now cultivated worldwide, from Texas to China. Sorghum is a particularly drought-tolerant grain and an essential part of the diet for 500 million people, chiefly in sub-Saharan Africa and India. In the U.S., where it is primarily grown for livestock feed, sorghum's climate resilience was highlighted during the devastating summer drought of 2012. A large international effort decoded the genome of the species cultivated for food, Sorghum bicolor, which was published in the journal Nature in 2009. That genome represents the genetic accounting of a single individual of sorghum. But as individual humans have genetic differences that underlie physical differences such as eye color, so do individual plants of sorghum. The focus of the current effort was to establish the connections between gene differences and physical differences – a detailed understanding of those connections will constitute a tremendous tool for plant breeders. The team behind the current PNAS publication – which also included researchers at Cornell University, the International Crops Research Institute for the Semi-Arid Tropics in India and Niger, the University of Illinois and the U.S. Department of Agriculture – used genotyping-by-sequencing (GBS) to determine the individual genetic makeup of 971 sorghum varieties taken from world-wide seed collections. The scientists identified more than a quarter million single-nucleotide polymorphisms (SNPs); that is, single letters in the genetic code where individual variants of sorghum can differ.