Grain filling is the physiological process for determining the obtainment of yield in cereal crops. The grain-filling characteristics of 50 maize brand hybrids released from 1964 to 2014 in China were assayed across multiple environments. We found that the grain-filling duration (54.46%) and rate (43.40%) at the effective grain-filling phase greatly contributed to the final performance parameter of 100-kernel weight (HKW). Meanwhile, along with the significant increase in HKW, the accumulated growing degree days (GDDs) for the actual grain-filling period duration (AFPD) among the selected brand hybrids released from the 1960s to the 2010s in China had a decadal increase of 23.41°C d. However, there was a decadal increase of only 19.76°C d for GDDs of the days from sowing to physiological maturity (DPM), which was also demonstrated by a continuous decrease in the ratio between the days from sowing to silking (DS) and DPM (i.e., from 53.24% in the 1960s to 49.78% in the 2010s). In contrast, there were no significant changes in grain-filling rate along with the release years of the selected hybrids. Moreover, the stability of grain-filling characteristics across environments also significantly increased along with the hybrid release years. We also found that the exotic hybrids showed a longer grain-filling duration at the effective grain-filling phase and more stability of the grain-filling characteristics than those of the Chinese local hybrids. According to the results of this study, it is expected that the relatively longer grain-filling duration, shorter DS, higher grain-filling rate, and steady grain-filling characteristics would contribute to the yield improvement of maize hybrids in the future.
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