In the shadow of a boisterous debate about the safety of growing crops that have been genetically modified, otherwise known as GMOs, the potential of good old-fashioned crossbreeding has been making quite a stir in the agricultural community.
A group of researchers recently took a closer look at the genome of sorghum, a drought-tolerant grass crop that feeds half a billion people in Asia and parts of sub-Saharan Africa. Unlike its super-cultivated cousins—corn, rice and soy—sorghum still grows in its original wild varieties, despite having been domesticated over 8,000 years ago. This diversity is as good as gold to the scientists, who say a cross between a domestic version of the plant and one of its wild relatives could produce a supercrop capable of feeding more people, withstanding pests and, most important, thriving in the face of climate change.
Like the schematic diagram in a user’s manual for a complex electronic device, a genome sequence lists an organism’s genetic parts—allowing scientists to then determine which chunks of its DNA are responsible for specific traits. While alleles, or alternate forms of a gene, control for specific characteristics such as plant height, a group of genes can influence how a plant responds to environmental stressors. “Some desirable traits, like drought tolerance or pest resistance, are absent in some species and present in others, but without access to the whole genome you can’t see that,” says Emma Mace of the Queensland Department of Agriculture, Fisheries and Forestry in Australia, and lead author of a study published in the August 27 issue of Nature Communications. The work lays the foundation for researchers interested in creating better crops the old-fashioned way, through cross-pollination of desirable strains.
Because sorghum’s wild and domestic varieties can be successfully interbred, future farmers of the crop could have access to a reservoir of genetic diversity, says study co-author David Jordan, associate professor with the Queensland Alliance for Agriculture and Food Innovation. The resulting strains could be stable enough for farmers to produce them generation after generation without returning to parent strains.
As with other popular food crops, sorghum’s domestic varieties succumbed to a trend known as genetic bottlenecking, which happens when farmers or breeders dramatically reduce the genetic diversity of a species by selecting for favorable traits such as sweeter fruit or bigger seeds. But cross one of these domesticated versions with a wild type of sorghum and another breed is born. “This opens up a new venue for people to pursue underexploited natural diversity,” says Clemson University professor of plant breeding and genetics Stephen Kresovich, who was not affiliated with the study but is collaborating with the Australian group in further research to exploit the sorghum genome sequence information.
In addition, the research provides insight into how genetic diversity is organized within an organism. Locating what he calls “hot pockets of useful traits” could help scientists create not just more productive crops but more efficient breeding programs as well, says Kresovich. That information would be of particular use to programs in developing nations, where it would enable scientists to target the traits they need without sacrificing the diversity critical to ensuring the crop’s success.