Case Western Reserve biologist explores wider uses for Namibian “orphan legume;” Marama bean grows in drought conditions and shows resistance to pests
and researcher Christopher Cullis said he pondered two big questions when he first
caught sight of the wild marama bean plant, its definitive patches of green
leaves standing out in contrast from among an otherwise parched and brown
“Why isn’t this
plant affected by the lack of water like everything else—and why isn’t it being
eaten by any wildlife?” Cullis said, turning one of the walnut-sized beans over
in his fingers and recalling his first trip to the coastal southwest African
country about a decade ago. “The answers to those questions make this a very
interesting and important legume.”
In fact, Cullis, the Francis Hobart Herrick
Professor of Biology at
Case Western Reserve University, and partners at universities from three
different African countries assert that the hardy-but-humble Tylosema esculentum could someday rise
up as a new alternative crop in the often-arid climates of developing countries.
They believe that, once cultivated, the marama bean could supplement food sources in Namibia and nearby countries and someday provide additional income for farmers through the sale of its oils and oversized tuber root, possibly as a starch alternative for baked goods.
Not only that, but
if its drought- and pest-resistant properties can be transferred to other plant
species, the marama bean could have an even wider impact, Cullis said.
“Other legumes shut
down under the stress of drought and then can’t be rejuvenated, even when
watered—but the marama bean never shuts down under the same drought condition,”
he said. “This helps inform us on how to make other legumes more drought-resistant,
and legumes are an important food source for much of the climate-challenged
Cullis has collaborated on marama research with scientists from Namibia University of Science and Technology, the Mulungushi University School of Agriculture and Natural Resources in Zambia and the Forestry and Agricultural Biotechnology Institute at the University of Pretoria, South Africa. Their most recent work was published in March in the journal Food and Energy Security.
The bean, endemic mostly to the Kalahari Desert region, is known to scientists as one of among numerous “orphan legumes” on the African continent, a description that references the dearth of genomic—or plant family—information known about it. Researchers like Cullis and his team are changing that as they dig deeper into understanding its molecular structure and learn more about how it thrives in water-scarce regions.
“Few others are
studying this, so we have now become the primary publishers on marama and have
the largest database in the world,” said Cullis, who returned in early April
from his most recent trip to Namibia, this time with a handful of biology
students to help with the research. “We have now sequenced the genome on a good
number of individual plants, and we are getting closer to fully understanding
The marama plant,
thanks in part to that massive tuber (weighing up to 500 pounds) retains moisture
better than other plants, possibly by recruiting fungi to help with the work.
And it is the seeds of the bean plant which seem to function as a pest
It has likely been a minor food source for the indigenous population for 1,000 years, however. They pick the bean from the wild patches, roast them (canceling out the toxicity that make them distasteful to other animals) and then eat them in a fashion similar to a peanut—“although it tastes a lot more like a cashew,” Cullis said.
There were failed
attempts to cultivate marama beans in the United States (Texas) and Australia several
decades ago, but Cullis said new research and understanding how to transplant
the bean might soon allow it to be farmed. Then it could serve as a subsistence,
or “rescue crop,” among locals—a possible buffer against food insecurity when other
crops fail in an increasing arid climate.
researchers associated with the pharmaceutical and cosmetic industries have
also shown interest in the seeds because they are abundant and rich in protein