Researchers turn up the heat to prepare for global warming

Vicky Boyd

Vicky Boyd,
Editor

When you start looking at historical weather data, Arkansas and the rest of the Southeast haven’t seen a significant overall temperature increase since the early 20th century.

What has changed in Arkansas and parts of the Southeast is how those temperatures are distributed, according to information from the National Oceanic and Atmospheric Association National Centers for Environmental Information.

Although the number of extremely hot days has not been unusual, mean summer temperatures and very warm nights (minimum temperature above 75 degrees Fahrenheit) from 2010–2016 were significantly greater than the long-term average.

Prolonged nighttime temperatures in the high 70s or above can take a toll on rice. Milling yields in 2010, for example, were the lowest on record due to high night temperatures throughout the Delta during the critical grain-fill period. Stressed plants produced fewer kernels with higher chalk. In 2016, growers saw lower yields because high night temperatures during pollination reduced flower fertilization.

These issues have not gone unnoticed as a number of studies are underway with long-term goals of developing climate change-ready rice varieties.

Paul Counce, a University of Arkansas rice physiologist, is leading a team to identify genes associated with resistance to high night temperatures. The work will be conducted in greenhouse growth chambers at the Rice Research and Extension Station in Stuttgart where they can carefully control environmental conditions. The researchers also will identify lines with genetic tolerance to high night temperatures for breeders to cross with high-yielding lines to develop improved varieties.

Meanwhile, an Arkansas State University-led research group is screening more than 320 rice lines from worldwide collections for tolerance to high night temperatures. Argelia Lorence, director of ASU’s phenomics, is heading the study with Wency Larazo, an ASU rice agronomist.

The researchers erected six specially designed movable greenhouses near Harrisburg this summer. Computers will open the greenhouses to allow in sun during the day for plant growth but will close three greenhouses at night to create temperatures 4 F warmer than ambient external air temperatures.

In addition, Christian De Guzman, a rice breeder at Southeast Missouri State University, is conducting trials to characterize the heat tolerance of N22, an upland variety from India known for its hardiness, along with several U.S. varieties. Among those are M-202, Titan, Presidio, MM17, Mermentau, CL111, Diamond, Thad, CL151, Lakast, CL172 and Wells.

All of these projects are turning up the heat to develop more resilient rice varieties.