Rising day and night temperatures are threatening rice, wheat, and maize production by disrupting plant growth, grain filling, and grain quality, putting global food security at risk. Precision breeding and genome editing offer ways to reprogram plant clocks, optimize flowering and panicle architecture, and protect grain quality under heat stress.
The world’s “cereal bowl,” or the production of rice, wheat, and maize, is under the dual challenges of a surging human population and a rapidly warming climate. As global temperatures rise, agricultural yields are failing to keep pace with demand, with scientists estimating that the rate of yield increase for these three staple crops must rise by a staggering 37% to ensure food security by 2050.
A particularly insidious and overlooked threat is the rise in high night temperatures, which are increasing nearly twice as fast as daytime temperatures. This nocturnal heat disrupts the delicate internal rhythms of plants, causing “source-sink” imbalances where the energy produced during the day is wasted through excessive respiration at night, ultimately leading to stunted grains and lower grain quality.
In a recently published review in Trends in Plant Science, scientists from the International Rice Research Institute and the Max Planck Institute of Molecular Plant Physiology analyzed how understanding the genetic regulation of flowering, plant architecture, and grain filling can provide a roadmap for developing climate-resilient varieties with sustained yield and grain quality. The authors argue that while the Green Revolution of the 20th century relied on stable, cooler climates, the current era requires precision breeding strategies to overcome the stagnation of crop production observed in low-income, food-deficit regions.
Reprogramming the plant’s biological clock
One of the most innovative solutions discussed in the review involves manipulating the plant’s circadian rhythm to help crops escape the worst of the heat. By identifying and tweaking “thermometer genes,” scientists can develop varieties that bloom earlier in the morning before temperatures peak.
In rice, for example, the gene OsMADS51 has been identified as a key factor in conferring thermotolerance during the critical heading and grain-filling stages. Similarly, in maize, researchers are targeting the “evening complex,” a group of genes including ZmELF3 and ZmLUX, which coordinates flowering and adaptation across different latitudes. By modifying these clock genes, breeders can ensure that the delicate process of flowering is promoted under heat stress.
Building a more efficient panicle architecture
Beyond timing, the inflorescence architecture of the plant can be re-engineered to maximize efficiency of grain number per panicle. The review highlights the potential of genes like DEP1 in rice, which produces dense, erect panicles that create a more favorable microclimate for the plant. These erect structures allow for better light distribution and photosynthetic rates, even under heat stress.
Furthermore, scientists are investigating the vascular highways of the plant, the bundles that transport sucrose to the developing grains. By identifying genes like SPIKE, GIF1, SPL14, and APO1-HI1, which increase the number of primary branches and vascular bundles, researchers can improve the “sink strength” of the grain, ensuring that nutrients are delivered effectively even when high temperatures threaten to disrupt the flow.