Rice plants exhibit resilience to daytime heat but require cooler temperatures at night. With rising nighttime temperatures in major rice-growing areas, breeders focus on developing rice varieties that can withstand these conditions.
Arkansas produces half of the rice in the United States, with approximately 1.4 million acres dedicated to this staple food, according to the USDA Economic Research Service. Professor Vibha Srivastava from the University of Arkansas highlights the challenges of incorporating tolerance genes into Arkansas rice, stating, "They have just started to scratch the surface in that area, but they're making good headway. Some promising updates are there."
Gene editing presents a potential solution, as it differs from traditional genetic modification by not inserting DNA from other organisms. Srivastava's article, co-authored with Christian De Guzman and Samual B. Fernandes, discusses gene editing's role in enhancing nighttime heat tolerance in rice, marking the first comprehensive review on this topic.
During flowering and grain-filling stages, rice is particularly sensitive to high nighttime temperatures, with most varieties showing vulnerability above 28°C (82.4°F). Such conditions can lead to yield losses of up to 90% and deterioration in grain quality, characterized by "chalkiness," which negatively affects milling and cooking.
While no modern cultivars in the U.S. can endure high nighttime temperatures, the Indian variety Nagina 22 shows promise. However, it presents undesirable traits like smaller grain size and increased chalkiness when cultivated in Arkansas. Efforts to cross Nagina 22 with modern cultivars have yet to clone the necessary genes for tolerance.
Additionally, recent studies indicate a warming trend in nighttime temperatures across the U.S., with a report stating a 1°F (0.53°C) increase in Arkansas's seasonal night air temperature from 1940 to 2018.