UGA researchers, working with the International Peanut Genome Initiative, have discovered that a wild plant from Bolivia is a “living relic” of the prehistoric origins of the cultivated peanut species.
The peanut that is grown by farmers today is the result of hybridization between two wild species. The hybrid was cultivated by ancient inhabitants of South America and, by selection, was transformed into today’s crop plant.
Comparisons of the DNA sequences of one of the wild species and the cultivated peanut showed that they are almost exactly same; in fact, they are 99.96 percent identical.
It’s an unprecedented similarity.
“It’s almost as if we had traveled back in time and sampled the same plant that gave rise to cultivated peanuts from the gardens of these ancient people,” said David Bertioli, an IPGI plant geneticist of the Universidade de Brasilia, who is working at UGA.
This discovery forms part of a study that appears in Nature Genetics journal, published by the UGA-led IPGI. Scott Jackson, director of the UGA Center for Applied Genetic Technologies in the College of Agricultural and Environmental Sciences, serves as chair of the IPGI. Bertioli is lead author on the paper.
Because its ancestors were two different species, today’s peanut carries two separate genomes, designated A and B subgenomes. Their high similarity means they are difficult to map out separately when sequencing the cultivated peanut genome. So, as a first step, researchers built their models using the two wild, ancestral peanut species collected by botanists in the wooded foothills of the Andes in Bolivia and Argentina decades ago.
The genome of one of them, Arachis duranensis, is about as similar to the A subgenome as could be expected. However, what really caught their attention was that the genome of the other species, A. ipaensis, was found to be virtually identical to the B subgenome.
Soon after botanists collected A. ipaensis in 1971, they realized that it was peculiar. The population of A. ipaensis was very small and isolated, and its closest relatives grew hundreds of miles to the north. They questioned how it arrived in the location where they found it growing.
Prompted by the extraordinary DNA identity, the scientists used information from decades-old botanical collections, knowledge of the seasonal movements of ancient hunter-gatherer-farmers and molecular DNA clock calculations to work out that the plants’ seeds had almost certainly been transported by humans about 10,000 years ago.
“Everything fit,” Bertioli said. “It’s the only place where A and B genome species have ever been found growing close together. The region is right next to the region where, even today, the most primitive types of cultivated peanut are grown, and the date is right in the time frame that plant domestication was happening in South America.”
The movement of the B genome species into the range of the A genome species meant that the hybridization could happen, probably courtesy of a native bee, and the cultivated peanut species was formed. The rest is history, Bertioli said.
The new peanut genome sequences were released in 2014 to researchers and plant breeders around the globe. The paper in Nature Genetics represents the first official publication of the IPGI.