Potential impact of increased heat tolerance of grain formation on maize yield under future warming

Variety has been a dominant factor in crop production to achieve high yield. Efforts to identify suitable crop varieties to increase yield under future climate conditions remains essential for sustainable agriculture development and food security. Previous studies have evaluated the impact of varietal changes on crop productivity under global warming, mostly in terms of varietal improvement that changed growing duration, growth characteristics and disease resistance. Potential impact of varietal improvement to increase the tolerance of grain formation to extreme temperatures has been rarely studied, particularly in the North China Plain (NCP). The objective of this study is to assess the likely impacts of future climate change scenarios on maize productivity in North China Plain (NCP), and evaluate the potential impact of using 'new' varieties with increased tolerance of grain number formation to high temperatures in response to climate warming. The 'new' maize variety, derived from existing variety Xundan29 in the APSIM model package, has a higher tolerance of pollen viability to high temperature. That is its grain number development has a higher maximum temperature threshold of 40 degrees C as compared to Xundan29 (38 degrees C). The process-based crop model APSIM, coupled with outputs of a regional climate model RegCM4, was used to simulate the impact of climate warming on maize yield in the periods of 2020-2045 based on RCP4.5 and RCP8.5 at Yuanyang, Yongnian and Shijiazhuang in the NCP. Results show that the reduction in maize yield caused by climate warming (without considering the contribution of variety adaptation) increased from northern to southern sites, by 12% on average, taking 1980-2005 as the baseline period. Introduction of a variety with increased tolerance of grain number formation to high temperature could be one of the effective adaptation strategies to offset the negative impact of climate change. It could lead to an average yield increase of 1-9% as compared to no adaptation, depending on sites and climate scenarios.