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

The replacement of winter wheat varieties has contributed significantly to yield improvement worldwide, with remarkable progress in China. Drawing on two sets of data, production yield from the National Bureau of Statistics of China and experimental yield from literature, this study aims to(1) illustrate the increasing patterns of production yield among different provinces from 1978 to 2018 in China,(2) explore the genetic gain in yield and yield relevant traits through the variety replacement based on experimental yield from 1937 to 2016 in China, and(3) compare the yield gap between experimental yield and production yield. The results show that both the production and experimental yields significantly increased along with the variety replacement. The national annual yield increase ratio for the production yield was 1.67% from 1978 to 2018, varying from 0.96% in Sichuan Province to 2.78% in Hebei Province; such ratio for the experimental yield was 1.13% from 1937 to 2016. The yield gap between experimental and production yields decreased from the 1970s to the 2010s. This study reveals significant increases in some yield components consequent to variety replacement, including thousand-grain weight, kernel number per spike, and grain number per square meter; however, no change is shown in spike number per square meter. The biomass and harvest index consistently and significantly increased, whereas the plant height decreased significantly.