Are Current Maize ( Zea mays L.) Cultivars Suitable Under Increasing Heat Stress Under Climate Change in China?

ABSTRACT Maize is a staple crop worldwide due to its extensive food, feed and industrial applications. With climate change, heat waves are becoming more frequent and intense, leading to a significant decrease in maize production. To meet the growing demand for maize products, it is critical to understand the mechanisms by which maize crops respond to heat stress. During anthesis, maize is particularly sensitive to heat, especially in the development of kernels, where kernel number is a major yield component. This sensitivity can vary considerably among different cultivars. However, studies on this topic have been infrequently reported thus far. We comprehensively reviewed controlled experiments from 13 independent, observation‐based publications and summarised the negative impacts of heat stress on maize yield and yield components. Our findings indicate that maize is more sensitive to heat stress after silking, particularly during the first 4 days following silking, compared to the period before silking. Moreover, maize yield is further reduced by increased maximum air temperature ( T max ) and accumulated heat degree days (HDD) for T max values exceeding 30°C. Among all the studied maize cultivars, the heating degree days threshold for mild heat stress ranged from 35°C·day in the heat‐sensitive cultivar to 59°C·day in the heat‐tolerant cultivar. Failing to select the appropriate heat‐tolerant cultivars for planting may lead to a significant reduction in maize production. Therefore, we strongly recommend that maize growers select heat‐tolerant cultivars or other varieties from the same series before planting to effectively combat climate change.