Effects of plant density on grain yield, protein size distribution, and breadmaking quality of winter wheat grown under two nitrogen fertilisation rates

• The effect of plant density on grain yield and quality differed between two N levels.
• The GPC was closely correlated with the amount and composition of protein fractions.
• Plant density affected quality primarily by changing glutenins polymerisation degree.

Nitrogen (N) and plant density are two crucial factors that affect winter wheat (Triticum aestivum L.) yield and quality, but little is known regarding the effects of interactions between these two factors on the amount and size distribution of protein fractions and quality traits. We grew the bread wheat cultivar Jinan17 in two successive seasons (2012–2013 and 2013–2014) at three densities of 120 plants m−2 (low), 180 plants m−2 [the usual rate for a multiple-spike cultivar with high tillering ability in the North China Plain (NCP)], and 240 plants m−2 (high) and two levels of N fertilisation of 0 (low N availability treatment without N fertilisation) and 240 kg ha−1 (the usual N rate for winter wheat production in the NCP) to evaluate the effect of N level × plant density interaction on grain yield, grain protein concentration, the amount and composition of protein fractions, dough development time, dough stability time, and loaf volume. The effect of plant density on Jinan 17 grain yield and quality differed between the two N levels. As plant density increased, all the parameters listed above decreased under 0 kg ha−1 N fertilisation, but increased under 240 kg ha−1 N fertilisation. Stepwise regression analysis showed that the dough rheological properties and breadmaking quality of Jinan 17 were affected by plant density under both N levels, primarily through changes in the polymerisation degree of glutenins in the flour.