Winter wheat yield improvement by genetic gain across different provinces in China1

The replacement of winter wheat varieties has greatly contributed to yield improvement worldwide and the progress in enhancing yield has been enormously achieved in China. Two sets of data, production yield from the National Bureau of Statistics of China (http://www.stats.gov.cn/english/) and experimental yield from literature, were used in this study for (1) displaying the increasing patterns of production yield among different provinces from 1978 to 2018 in China (2) exploring the genetic gain in yield and yield relevant traits through the varieties replacement based on experimental yield from 1937 to 2016 in China (3) comparing the yield gap between experimental yield and production yield. The results showed that both the production and experimental yield showed significantly increase trends along with the varieties replacement. For the production yield, the annual yield increase ratio was 1.67% at national scale from 1978 to 2018, varying from 0.96% in Sichuan Province to 2.78% in Hebei Province. In term of experimental yield, there was an annual yield increase ratio at 1.13% from 1937 to 2016 in this study. The yield gap between experimental yield and production yield showed decreasing trends from 1970s to 2010s. Regarding the yield components, the significant increased trend appeared in thousand grain weight, kernel number per spike, and grain number per square meter, while no change showed in spike number per square meter along with the variety replacement. The biomass and harvest index showed consistently significant increased, whereas the plant height was significantly decreased.