Rising emissions may double sweet potato size

[LIMA] Rising levels of carbon dioxide (CO2) in the atmosphere caused
by human-driven emissions might lead to larger sweet potatoes, a
staple food for many African and Asian countries, research reveals.
Sweet potatoes could double in size with the increase in CO2 levels
currently forecasted for the end of this century, according to
research by a team from the University of Hawaii, United States. The
team  presented their finding at a meeting of the American Geophysical
Union, in San Francisco this month (3-7 December).
The researchers grew a white-fleshed sweet potato variety from Hawaii
in two types of fertiliser at current CO2 levels of 352 parts per
million (ppm), as well as in three raised CO2 environments: 763, 1,108
and 1,515 ppm.
According to the Intergovernmental Panel on Climate Change,
atmospheric CO2 levels will be between 500 and 1,000 ppm by the year
Even at 763 ppm of CO2, the tubers grew up to 96 per cent larger.
“It is more than likely that we will be reaching much higher CO2
levels than previously expected and it is therefore important to
understand how plants will respond to elevated CO2 at much higher
concentrations,” Ben Czeck, one of the researchers, tells SciDev.Net.
n addition, he says that climate change is expected to do the most
harm to developing countries that rely heavily on root crops such as
sweet potato.
The researchers now want to find out if growing larger sweet potatoes
will have any negative impact on their nutritional content, Czeck
Previous studies revealed that the protein content in wheat, rice,
barley and potatoes dropped by 15 per cent when grown under CO2 levels
double those of today. The drop is caused by a series of impacts on
plant physiology stemming from the higher levels of the gas.
“The nutritional contents we are looking at are calories, dietary
fibre, protein, sugars and micro- and macro-minerals,” Czeck says.
Orange- and purple-fleshed varieties of sweet potato are rich in
beta-carotene, which the body converts to vitamin A. They are being
grown to try to reduce child malnutrition in African countries.
Gabriela Burgos, who leads the Quality and Nutrition Lab at the
International Potato Center (CIP), in Peru, says it is vital to study
how raised CO2 levels will affect root and tuber crops, because much
of the world’s population depends on them for food.
“At CIP, we are trying to add more nutritional content to potato and
sweet potato varieties, but if in a few years those varieties are
going to be oversize, their nutritional content could be diluted,” she
tells SciDev.Net. So it is good to have some way of dealing with the
anticipated changes, she adds.
But Wolfang Gruneberg, CIP geneticist and sweet potato breeder, thinks
the real problem will not be higher atmospheric CO2 levels but the
effect of raised temperatures on plants.
“Plants use water to cool down. There are many places in the tropical
world with drought. So the problem is not going to be the carbon
dioxide but the [extra] heat that it would generate,” he says.
CIP is evaluating the temperature range that sweet potatoes can
withstand. As part of this, Gruneberg is planting a number of sweet
potato varieties from CIP’s genebank — the most complete of the world
— in the hottest areas in north Peru.
(Source: SciDev via ENN)

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