Thousands of years ago, farmers in West Africa took a wild ancestor of rice and turned it into a crop of their own. But it was difficult to harvest and, over time, globally dominant Asian rice pushed it aside. Yet African rice survived in some of the region's harshest growing conditions, coping with drought, deep water, poor soil, pests and punishing heat. Now, researchers in China may have found a way to make its hard-won traits easier for breeders to harness.
Put the two plants side by side and the untrained eye would struggle to tell them apart.
“They're going to look very similar to each other, but they evolved differently,” Michael Purugganan, a New York University evolutionary biologist who has spent years studying the domestication of rice, told RFI.
Asian rice, Oryza sativa, was domesticated along China's Yangtze River around 9,000 years ago – thousands of years before West African farmers domesticated Oryza glaberrima, Purugganan said.
Yet far less is known about how that second domestication happened.
“We don't know as much as we do about Asian rice, largely because the archaeology in that part of the world is not as well developed as in Asia,” Purugganan explained.
Genetic research into the crop's history has also gathered pace only in recent years. African rice largely remained in West Africa, although some crossed the Atlantic with enslaved Africans and was grown for a time in the Americas.
Asian rice followed a very different path. It spread around the world and eventually came to dominate even in Africa, where it increasingly replaced the indigenous crop farmers had developed.
There were practical reasons for the shift. African rice can be frustrating to harvest, shedding ripe grain before it can be collected and collapsing in the field as its stems weaken late in the growing season.
But the plant held on in some of West Africa's most difficult growing environments, including dry uplands and areas of deep water, said Koichi Futakuchi, a veteran rice scientist at the Africa Rice Centre, a pan-African research body based in Cote d’Ivoire.
Scientists have recognised its potential for decades. One African rice line, CG14, “possesses resistance to multiple stresses in Africa such as iron toxicity, drought, deep water, striga [a parasitic weed] and nematodes [microscopic worms that attack roots]”, Futakuchi said.
The challenge has been getting more of those qualities into Asian rice.
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