An exploration of the genomes of 13 rice species has revealed an evolutionary path that could inspire more resilient versions of the crop that feeds half the world. Possibly the richest finds come from crocodile-infested wetlands in northern Australia, which have preserved a very ancient species of rice with features rice breeders have been seeking.
The rice on our plates is either Oryza sativa or Oryza glaberrima; the first was domesticated in Asia 10,000 years ago, while the latter underwent the same process independently in Africa 7,000 years later. Yet other species genetically similar enough that they can easily interbreed with these two possess genes that could be a goldmine for the future of global food security.
A paper in Nature Genetics describes the differences between these strains, and provides a timeline of their divergence. Of particular interest is O. meridionalis, found in wet tropical regions of Australia and the most similar to the ancestor of all rice. Although long harvested by Indigenous Australians, it has never been domesticated, and until recently was ignored by white Australians.
The University of Queensland's Professor Robert Henry, one of the paper's 65 authors, thinks that is a mistake. “It tastes good and we believe it may have more beneficial health qualities than other rice species,” Henry said in a statement.
“The higher the amylose content, the longer the rice takes to digest. This potentially offers more nutrition to our gut microbes, in the same way high-fiber foods do.” These theoretical benefits have yet to be tested in nutritional trials, a reflection on how we're only just starting to investigate meridionalis' potential.
However, it is unlikely there will be a sudden rush for wild rice to displace sativa or glaberrima at the dinner table. Thousands of years of artificial selection have made the two existing crops well suited to mass production. Instead, hybrids with the most useful genes are likely to be produced, offering resistance against disease and drought.
The paper reveals meridionalis diverged from other rice species some 2.4 million years ago, which Henry noted is about the time human ancestor Lucy lived. Two other Australian species have been separated for from the rest of the rice family for so long they struggle to interbreed easily, making them of less interest.
“[This study] Helps us to identify which species we can cross rice crops with, and to look for particular traits in the gene pool. This sort of knowledge is fundamental to breeding new varieties.” Henry told IFLScience.
The paper also includes the first complete assembly of the genome of IR 8, the breed of rice that helped spark the “Green Revolution” and enable Asia to feed its growing population.