Effect of nitrogen application rate on content of glutenin macropolymer and high molecular weight glutenin subunits in grains of two winter wheat cultivars

Two winter wheat (Triticum aestivum L.) cultivars differing in grain protein content were selected to study the effect of N application rate on changes in contents of glutenin macropolymer (GMP) and high molecular weight glutenin subunits (HMW-GS) during grain filling. Contents of GMP and HMW-GS were much higher in the high GPC cultivar, Xuzhou 26, than those in low GPC cultivar, Ningmai 9. N increased contents of GMP and HMW-GS in Xuzhou 26 with N rate between 0 and 300 kg ha−1, while at the very high N rate of 300 kg ha−1 the contents of GMP and HMW-GS in Ningmai 9 decreased. The high contents of GMP and HMW-GS at maturity were closely related to the rapid increase in contents of GMP and HMW-GS during the initial period of their synthesis. HMW-GS and GMP content were closely correlated. The total HMW-GS content was important in determining GMP content than the content of any HMW-GS pair or any individual HMW-GS present in the selected cultivars. The pattern of response of GMP content to N application rate was closely related to the regulatory effect of N on HMW-GS synthesis.