| Nitrogen is an essential element for plant growth and development.In the last century,higher input of the artificial nitrogen fertilizer means higher crop yield;however,it also brought a big challenge—decreased nitrogen use efficiency(NUE).Therefore,one of the hottest areas of research currently is enhancing NUE in wheat based on high and stable yield.Since 2000,many cultivars have been released in the middle and lower reaches of the Yangtze River and the Huang-Huai-Hai plain,from which it was important to identify the synergistic and key agronomic characteristics of high-yield and-efficiency,and good quality cultivars,and to establish appropriate nitrogen saving conditions that allow them to reach their full potential in high-yield and-NUE,so as to achieve high yield,high efficiency and sustainable development of wheat in these two regions.The field experiments were conducted on the farm of Jiangsu Key Laboratory of Crop Cultivation and Physiology of Yangzhou University which was located in the middle and lower reaches of the Yangtze River,and the Modern Agricultural Center of Suining which was located in the Huang-Huai-Hai plain from 2016 to 2021.21 spring and 22 semi-winter wheat cultivars that were widely cultivated in the two regions were selected,respectively.The characteristics of population quality,nitrogen accumulation,distribution and transportation,and grain quality among wheat cultivars with different grain yield and NAE(nitrogen agronomic efficiency)were analyzed in accordance with the cooperation of grain yield and NAE among cultivars,to identify the synergistic mechanism and key agronomic traits of high-yield and-efficiency of wheat.To investigate the effect of different ecology on grain yield,NUE,and grain quality of spring and semi-winter wheat cultivars,seven spring and six semi-winter wheat cultivars were planted Yangzhou and Suining,respectively.Different grain yield and NAE cultivars were selected from experiments and built different N saving methods to explore the response mechanism of cultivars with high grain yield and NAE under nitrogen saving.The main results are as follows:1.The grain yield and NAE of spring and semi-winter wheat cultivars released in recent years were synergistic.Spring wheat cultivars with high-yield and-NAE(grain yield and NAE were 7.3 t ha-1and 19 kg kg-1,respectively)had high spike number,single spike yield,and AEN,which were 390×104 ha-1,2 g,and 53%,respectively.High total grains(high spike number and grains per spike),AEN and nitrogen utilization efficiency(NUtE),which were 2.1×108 ha-1、47%and 41 kg kg-1,respectively,were characteristics of semi-winter wheat cultivars with high-yield and-NAE.2.Spring and semi-winter wheat cultivars with high-yield and-NAE had significantly higher tiller fertility(by 24%and 36%,respectively)than that of other types,resulting in an increased spike number and nitrogen accumulation before anthesis,possibly due to developed root growth.Nitrogen distribution in leaves per stem of spring wheat and population leaves of semi-winter wheat were increased because plants accumulated more nitrogen at anthesis,which were 14 mg and 59 kg ha-1,respectively.The nitrogen accumulation per unit leaf area of cultivars with high-yield and-NAE(by 160 μg and 130 μg,respectively)were increased,which was helpful to promote photosynthetic production after anthesis.Increasing of single spike yield of spring wheat and grains per spike of semi-winter wheat were achieved.3.High-yield and-NAE of spring and semi-winter wheat cultivar types have significantly higher nitrogen accumulation per grain than other cultivar types.Compared with low-yield and-NAE type,the nitrogen accumulation per grain of spring cultivar type with high-yield and-efficiency was higher by 9.7%(2017)、8.0%(2018)and 6.3%(2019),and 1000-grain weight was higher by 10.0%(2017),7.5%(2018)and 6.0%(2019),their increase magnitude was similar.Therefore,there was no significant difference in grain quality of spring cultivar types.Protein content,wet gluten content,sedimentation value,and flour quality of high-yield and-efficiency of semi-winter cultivars were significantly higher than those of other types.The nitrogen accumulation per grain was decreased,when the grain yield exceeded 9.5 t ha-1 or total grains exceeded 2.2×108 ha-1.4.The grain yield and NAE of wheat cultivars planted in Suining were significantly higher than those in Yangzhou.Although the grain yield and NAE of spring wheat cultivars planted in Suining were improved,the differences were not significant compared to local cultivars,and their stability was poor for two years.Grain yield and NAE of semi-winter wheat planted in Yangzhou were decreased.The factors contributed to the high yield of wheat planted in Suining were that the average temperature of Suining was lower than Yangzhou during the early growth period,which prolonged the vegetative growth period and helped to improve tiller fertility,this resulted in an increase the population and delayed the decline of leaf area after anthesis,which enhanced photo synthetic production,ultimately,improved grain yield.High NUtE was attributed to improving NAE.5.The dough development time,stability time of flour curve and farinograph quality number of wheat grown in Suining were higher than in Yangzhou,while the degree of softening was significantly lower in Suining than in Yangzhou.The protein content and flour quality of spring wheat grown in Suining were better than in Yangzhou,the grain quality of semi-winter wheat planted in Yangzhou decreased.These results indicated the differences in ecological conditions increased the instability of wheat cultivar grain quality.The correlation of coefficient of variation(CV)of grain yield,NUE and grain quality indicated that flexible efficiency ears,biomass after anthesis,NUtE,and stable single spike yield were beneficial to release the potential of grain yield and NAE,while variable NUtE was not good for grain quality stability.6.Compared with traditional nitrogen application(225 kg ha-1),the nitrogen application was reduced by 20%,and nitrogen fertilizer was applied to 90 kg ha-1 at the base and elongation stage(M4),although the tiller number decreased,the stable spike number was maintained by high tiller fertility of high-yield and-NAE cultivar,and LAI,SPAD value,and Pn at anthesis and SPAD value and Pn at milk-ripe stage were stable,larger LAI at the milk-ripe stage increased dry matter accumulation after anthesis by 10%,and ensure stable grains per spike and 1000-grain weight.Reduced nitrogen application reduced tiller number and did not significantly increase tiller fertility of other types,resulting in fewer spike number,and decreased photosynthetic capacity of leaf after anthesis,ultimately decreasing grain yield.7.Compared with CK(225 kg ha-1 N),a 20%reduction in nitrogen application significantly increased the expression of nitrate transporter genes in the secondary root,root length density,and root weight density in 0-40 cm soil layer,and kept stable enzyme activity of root nitrogen metabolism in root of high-yield and-NAE cultivar after the elongation stage,which improved nitrogen uptake capacity in root,and maintained nitrogen accumulation stable in plant,which was conducive to maintaining grain yield and improving AEN.Reduced nitrogen rate decreased nitrogen accumulation of other types due to weak root growth,nitrogen absorption and assimilation capacity in roots.Grain yield was decreased,and AEN was not improved or even decreased.8.Significant differences in protein content,wet gluten content,and sedimentation value were observed among cultivars,with Ningmai 21 being the highest and Yangmai 25 being the lowest.Dough development time,stability time of flour curve and farinograph quality number of high-yield and-NAE cultivar(Yangmai 25 and Ningmai 21)were higher than those of other types(Yangmai 20 and Yangmai 22).Reduced nitrogen rate decreased the protein content,wet gluten content,sedimentation value,and flour quality of cultivars of all cultivars.Under M4 method(90 kg ha-1 N applicated at basal and elongation stage),protein content,wet gluten content,and sedimentation value of all cultivars were promoted to a certain extent,however,only the four flour qualities of high-yield and-NAE cultivar were improved. |
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