LAUSR

BACKGROUND Sowing date, seeding rate, and nitrogen (N) topdressing ratio have strong effects on grain yield (GY) and bread-making quality (BQ) in bread wheat. Simultaneous improvement in GY and BQ in bread wheat has long been a challenge due to the inverse relationship between GY and grain protein concentration (GPC). In this study, we investigated whether the GY and BQ of bread wheat sown on different dates could be improved simultaneously by optimising the seeding rate and N topdressing ratio. RESULTS Delaying sowing beyond a certain period led to decreases in both GY and BQ. Optimising seeding rate and N topdressing ratio enhanced N uptake during pre- and post-anthesis, as well as N remobilisation during grain filling for all wheat plants sown on different dates, thereby increasing GPC and the total N per grain (Ntot ). Consequently, grain protein composition was improved, resulting in increased glutenin/gliadin ratio, sodium dodecyl sulphate-insoluble glutenin/total glutenin (i.e., glutenin polymerisation index), and HMW-GS/LMW-GS ratio. Increased GPC and improved grain protein composition enhanced BQ. CONCLUSION The mechanism underlying simultaneous improvement in GY and GPC as well as Ntot was the greater increase in N accumulation in grains per unit area relative to increases in GY or total grain number per unit area. GY and BQ can be improved simultaneously regardless of sowing date by optimising seeding rate and N topdressing ratio via enhanced N uptake and N remobilisation into grains. This article is protected by copyright. All rights reserved.