Night warming increases wheat yield by improving pre-anthesis plant growth and post-anthesis grain starch biosynthesis

Global climate change is characterized by asymmetric warming (i.e., greater temperature increases in winter, spring, and nighttime than in summer, autumn, and daytime). Field experiments were conducted using four wheat cultivars, namely ‘Yangmai 18’ (YM18), ‘Sumai 188’ (SM188), ‘Yannong 19’ (YN19), and ‘Annong 0711’ (AN0711), in the two growing seasons of 2019–2020 and 2020–2021, with passive night warming during different periods in the early growth stage. The treatments were night warming during the tillering–jointing (NWT-J), jointing–booting (NWJ-B), and booting–anthesis (NWB-A) stages, with ambient temperature (NN) as the control. The effects of night warming during different stages on wheat yield formation were investigated by determining the characteristics of dry matter accumulation and translocation, as well as sucrose and starch accumulation in wheat grains. The wheat yield of all four cultivars were significantly higher in NWT-J than in NN in the 2-year experiment. The yield increases of semi-winter cultivars YN19 and AN0711 were greater than those of spring cultivars YM18 and SM188. NWT-J increased wheat yield mainly by increasing the 1000-grain weight and the number of fertile spikelets. NWT-J increased dry matter accumulation in various organs of wheat at the anthesis and maturity stages by increasing the growth rate at the vegetative growth stage. The flag leaf and spike showed the largest increases in dry matter accumulation. NWT-J also increased grain sucrose and starch content in the early and middle grain-filling stages, promoting yield formation. Overall, night warming between the tillering and jointing stages increased the pre-anthesis growth rate, and thus, wheat dry matter production, which contributed to the increase in wheat yield.