30 Heat-Tolerant Beans Identified, Poised to Endure Warming World

Black beans, kidney beans, pinto beans, navy beans and pink beans—varieties of what is called the common bean—provide essential protein and vitamins the world over, especially in Latin America and Africa.  But according to a recent climate model, increasing temperatures could take those beans off the table for up to 50 percent of their growing areas by 2050, making temperature rise a greater threat to this staple food than even drought or disease.

In response, the International Center for Tropical Agriculture (CIAT) dug into its seed repository and struck gold.   After testing more than 1,000 bean varieties they had developed during other projects, investigators identified around 30 that revealed some ability to produce seeds in spite of toasty night temperatures.  Those beans have the potential not only to survive increasing temperatures, but to thrive.  In fact, they might even expand the area where beans can be grown.

The researchers focused on night temperatures because common beans, which are a primary source of protein for over 400 million people, can produce viable pollen only if the nights are cool.  They often do best at raised elevations, where nighttime temperatures reach no higher than 18 degrees Celsius (around 64 degrees Fahrenheit).

“The common bean originated in the hills and mountains, so it’s not especially well adapted to coastal areas and high temperatures,” says Stephen Beebe, CIAT’s bean program leader.  “Now, with climate change, the high temperatures aren’t staying down at the coast—they’re going up the hill.”

Researchers had calculated that beans able to withstand a temperature rise of about 4 degrees Celsius (7.2 degrees Fahrenheit) would be able to stay in most of today’s bean-growing locations until at least 2050 and potentially expand into other areas where beans currently cannot grow due to the heat.  Beebe and his colleagues therefore decided to test 1,000 candidates in Colombia’s Caribbean Coast, a low-altitude area where night temperatures can hit that level, heating up to 23 or 24 degrees Celsius.  Many of the selected plants had previously been bred to withstand drought, resist disease and have higher iron content.  The ones that thrived when grown in the open air during the experiment were easy to find: although most of the plants tested produced no seed pods at all or generated shriveled seeds, 30 lines managed to produce viable seeds—up to 1000 kg in one trial, Beebe says, when the others yielded nothing.  Beebe announced the discovery Tuesday at a conference in Addis Ababa, Ethiopia.

Many of the beans that beat the heat had a common ancestor in their family trees:  tepary beans, which are tiny, drought- and heat-tolerant beans that grow in the southwestern U.S. and northern Mexico.  They have fallen out of favor because of their small size, but at one time the near-desert’s inhabitants would rush out and plant them after a rain shower—often the only time the plants would have access to water for their whole lifespans.  So it makes sense that beans with tepary ancestry might have a leg up on heat tolerance as well as drought tolerance.

Read more at 30 Heat-Tolerant Beans Identified, Poised to Endure Warming World