In order to find out the way to achieve further improvement in the grain yield (GY) and nitrogen use efficiency (NUE) of winter wheat, two sowing pattern (the wide range sowing and conventional drilling sowing) and seven planting densities (130×10 4 , 200×10 4 , 270×10 4 , 340×10 4 , 410×10 4 , 480×10 4 , and 550×10 4 plants hm-2) were designed during 2015-2016 and 2016-2017 growing seasons. Tainong 18, a winter wheat cultivar with larger spike and lower tillering capacity, was used to investigate the combined effects of sowing pattern and planting density on GY and NUE. Compared with the conventional drilling sowing, the wide range sowing with higher planting density effectively alleviated the negative effect of increasing spikes per unit area and nitrogen uptake efficiency (NUpE) on decreasing single spike weight and nitrogen utilization efficiency (NUtE), respectively. Concurrent improvement in GY and NUE was achieved by increasing the number of spikes per unit area and NUpE. The planting density resulting in the highest GY and NUE under wide range sowing conditions was 410×10 4 plants hm-2 , which was significantly higher than that (340×10 4 plants hm-2) under conventional drilling sowing. Moreover, the increase percentage of GY and NUE under wide ranging sowing was also significantly higher than that under drilling sowing. In summary, it is feasible to further improve GY and NUE of large spike wheat cultivar through rational combination of wide range sowing with higher planting density. Under the condition of this experiment, the optimal combination measure for high GY and NUE was sowing width of 8-10 cm with plant density of 410×10 4 plants hm-2 .

BACKGROUND: Sowing date, seeding rate, and nitrogen (N) topdressing ratio have strong effects on grain yield (GY) and breadmaking 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 optimizing the seeding rate and the N topdressing ratio.RESULTS: Delaying sowing beyond a certain period led to decreases in both GY and BQ. Optimizing the seeding rate and N topdressing ratio enhanced the N uptake during pre-and post-anthesis, as well as N remobilization during grain filling for all wheat plants sown on different dates, thereby increasing the GPC and the total N per grain (N tot ). Consequently, grain protein composition was improved, resulting in an increased glutenin/gliadin ratio, sodium dodecyl sulfate-insoluble glutenin/total glutenin (i.e., glutenin polymerization index), and high-molecular-weight glutenin subunit/ low-molecular-weight glutenin subunit (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 N tot was the greater increase in N accumulation in grains per unit area relative to increases in GY, or total grain number per unit area. The GY and BQ can be improved simultaneously regardless of sowing date by optimizing the seeding rate and N topdressing ratio via enhanced N uptake and N remobilization into grains.

Background and AimsClimate warming has become an indisputable fact, and wheat is among the most heat-sensitive cereal crops. Heat stress during grain filling threatens global wheat production and food security. Here, we analyzed the physiological and proteomic changes by delayed sowing on the photosynthetic capacity of winter wheat leaves under heat stress. Our aim is to provide a new cultivation way for the heat stress resistance in wheat.MethodsThrough 2 years field experiment and an open warming simulation system, we compared the changes in wheat grain weight, yield, photosynthetic rate, and chlorophyll fluorescence parameters under heat stress at late grain–filling stage during normal sowing and delayed sowing. At the same time, based on the iTRAQ proteomics, we compared the changes of differentially expressed proteins (DEPs) during the two sowing periods under high temperature stress.Key ResultsIn our study, compared with normal sowing, delayed sowing resulted in a significantly higher photosynthetic rate during the grain-filling stage under heat stress, as well as significantly increased grain weight and yield at maturity. The chlorophyll a fluorescence transient (OJIP) analysis showed that delayed sowing significantly reduced the J-step and I-step. Moreover, OJIP parameters, including RC/CSm, TRo/CSm, ETo/CSm, DIo/CSm and ΦPo, ψo, ΦEo, were significantly increased; DIo/CSm and ΦDo, were significantly reduced. GO biological process and KEGG pathway enrichment analyses showed that, among DEPs, proteins involved in photosynthetic electron transport were significantly increased and among photosynthetic metabolic pathways, we have observed upregulated proteins, such as PsbH, PsbR, and PetB.ConclusionPhysiological and proteomic analyses indicate delaying the sowing date of winter wheat reduced heat dissipation by enhancing the scavenging capacity of reactive oxygen species (ROS) in flag leaves, and ensuring energy transmission along the photosynthetic electron transport chain; this increased the distribution ratio of available energy in photochemical reactions and maintained a high photosynthetic system assimilation capacity, which supported a high photosynthetic rate. Hence, delayed sowing may represent a new cultivation strategy for promoting heat stress tolerance in winter wheat.