| The significant differences in grain yield and nitrogen use efficiency among different wheat varieties were investigated to clarify the characteristics of high-yield and high-nitrogen use efficiency wheat varieties with low-nitrogen tolerance,which can provide a basis for the selection of high-yield and high-efficiency varieties and new variety selection and breeding in wheat production.On the basis of this,30 winter wheat varieties,which are the main varieties promoted in the Huanghuaihai Plain,were selected as test materials for two consecutive wheat growing seasons in 2019-2020 and 2020-2021,and the field trials were conducted in Dongwu Village,Dawenkou Town,Tai’an,Shandong,P.R.China.According to the grain yield and nitrogen utilization efficiency of each variety,the varieties were divided into four types:high yield and high efficiency type（HH）,high yield and low efficiency type（HL）,low yield and high efficiency type（LH）and low yield and low efficiency type（LL）.Low nitrogen treatment（NO）will be added on the basis of normal nitrogen application treatment（N240）from 2020 to 2021,and each variety was classified into two types,low N-sensitive and low N-tolerant,based on the low N tolerance index and the integrated N efficiency index,and a systematic comparison was made between the varieties.The differences in yield composition,population and nitrogen accumulation and transport among the varieties were systematically investigated in order to clarify the high-yield N-efficient and low-N-tolerant characteristics of different wheat varieties.The main findings were as follows.1.Nitrogen efficiency types of wheat varietiesUnder the normal nitrogen supply level,based on the classification results of varieties in the two growth seasons,five varieties with high yield and high efficiency were determined,which were Luyuan 502,Liangxing 99,Shannong 29,Qingnong 2 and Tainong 19 respectively;Five varieties with high yield and low efficiency were Jinan 17,Yannong 19,Jimai 229,Taimai 198 and Tainong 33 respectively;Four varieties with low yield and high efficiency were Hemai 19,Linmai 4 and Shannong 32 respectively;Three varieties with low yield and low efficiency were Qimai 2,Taishan 28 and Taishan 27 respectively.Under different nitrogen supply levels,according to the comprehensive value of nitrogen efficiency and low nitrogen tolerance index of different varieties,nine low nitrogen tolerant varieties were determined,namely Luyuan 502,Shannong 29,Liangxing 99,Yannong 19,Jinan 17,Jimai 229,Denghai 202,Yannong 999 and Jimai 23;Nine low nitrogen sensitive varieties were Qimai 2,Shannong 30,Linmai 4,Taishan 27,Xinmai 296,Zhouyuan 9369,Hemai 19,Taishan 28 and Shannong 32.According to the comprehensive analysis,there are three wheat varieties with high yield,high efficiency and low nitrogen tolerance,namely Luyuan 502,Liangxing 99 and Shannong 29.2.Yield composition characteristics of different types of wheat varietiesThe yield of high yield and high efficiency wheat mainly benefits from the higher number of panicles per unit area and grains per unit area.The yield of high-yield nitrogen efficient and high-yield nitrogen inefficient varieties was 12.15%and 10.78%higher than that of low-yield and high efficient varieties,the number of panicles per unit area was 11.91%and 17.22%higher,and the number of grains per unit area was 16.74%and 14.68%higher,respectively;The yield of low nitrogen and low efficiency varieties was 17.59%and 16.15%higher,the number of panicles per unit area was 13.21%and 16.84%higher,and the number of grains per unit area was 18.22%and 19.36%higher,respectively.There was no significant difference in grain number per panicle and grain weight among wheat varieties with different nitrogen efficiency types.The yield of low nitrogen tolerant wheat varieties also mainly benefited from the higher number of panicles per unit area and grains per unit area.Under the normal nitrogen application level,the yield,panicles per unit area and grains per unit area of low nitrogen tolerant varieties were 22.60%,18.44%and 17.00%higher than those of low nitrogen sensitive varieties,respectively;Under low nitrogen level,it was 30.17%,20.27%and 17.41%higher respectively,but there was no significant difference in grain number and grain weight per panicle between the two types of varieties.3.Population characteristics of different types of wheat varietiesThe yield of high-yield and high-efficiency varieties mainly comes from the higher dry matter production before and after anthesis and the contribution rate of dry matter production after anthesis to grain.The dry matter accumulation at flowering stage of high-yield nitrogen efficient and high-yield nitrogen inefficient varieties was 9.32%and 9.44%higher than that of low-yield nitrogen efficient varieties,13.73%and 12.86%higher at maturity,23.23%and 20.24%higher after anthesis,9.73%and 8.73%higher than that of high-yield and high efficient varieties,9.32%and 8.44%lower than that of low-yield nitrogen efficient varieties,and 22.60%and 20.37%lower than that of pre anthesis,The contribution rate of pre anthesis dry matter to grain was 22.85%and 19.95%lower,respectively;Compared with the low nitrogen yield and low efficiency varieties,the dry matter accumulation at flowering stage was 14.54%and 14.66%higher,the dry matter accumulation at maturity stage was 19.60%and 18.69%higher,the dry matter accumulation after anthesis was 30.71%and 27.50%higher,the contribution rate of dry matter accumulation after anthesis to grain yield was 10.43%and 9.41%higher,the dry matter transport before anthesis was 4.83%and 3.97%lower,and the dry matter transport rate before anthesis was 20.07%and 19.17%lower,respectively,The contribution rates of pre anthesis dry matter transport to grain yield were 24.41%and 21.42%lower,respectively.The dry matter accumulation and dry weight of vegetative organs in anthesis and mature stage of low nitrogen tolerant varieties were significantly higher than those of low nitrogen sensitive varieties.Under the normal nitrogen application level,the dry matter accumulation and dry weight of aboveground vegetative organs in anthesis and mature stage of low nitrogen tolerant varieties were 24.42%,18.33%and 25.78%higher than those of low nitrogen sensitive varieties respectively,and 32.28%,27.63%and 34.36%higher under the low nitrogen level.High-yield and high-efficiency wheat varieties have the characteristics of more tillers and more degradation,but the dry matter loss and nitrogen loss caused by ineffective tiller degradation did not affect the acquisition of high yield and high nitrogen efficiency.The number of ineffective tillers,dry matter loss and nitrogen loss of high-yield and high-efficient type were 17.13%,22.07%and 21.83%higher than those of low-yield and high-efficient type,17.12%,26.64%and 28.76%higher than those of low-yield and low-efficient type,17.63%,21.05%and 19.38%higher than those of high-yield and high-efficient type,17.35%,25.57%and 26.32%higher than those of low-yield and low-efficient type.Low nitrogen tolerant wheat varieties also had similar population characteristics.4.Nitrogen accumulation and transport characteristics of different types of wheat varietiesThe high nitrogen efficiency of high-yield and high-efficiency varieties is mainly due to the high pre anthesis nitrogen transport rate and the contribution of pre anthesis nitrogen to grain nitrogen.The nitrogen accumulation of high-yield nitrogen efficient and high-yield nitrogen inefficient varieties at flowering stage was 23.23%and 20.24%higher than that of low-yield and high-efficient varieties,and 13.27%and 23.65%higher at maturity,respectively;Compared with the low-yield and low-efficiency varieties,the nitrogen accumulation at flowering stage was 30.71%and 27.50%higher,and the nitrogen accumulation at maturity stage was 7.44%and 17.24%higher,respectively.The pre anthesis nitrogen transport rate of high-yield nitrogen efficient and low-yield nitrogen efficient varieties was higher than that of low-yield and high-efficient varieties,which was 9.63%and 11.30%higher respectively.The contribution rate of pre anthesis nitrogen to grain nitrogen was 5.86%and 7.36%higher respectively,and the contribution rate of post anthesis nitrogen to grain nitrogen was 14.21%and 18.88%lower respectively;Compared with the low-yield and low-efficiency type,the pre anthesis nitrogen transport rate was 8.13%and 9.79%higher,the contribution rate of pre anthesis nitrogen to grain nitrogen was 4.90%and 6.39%higher,and the contribution rate of post anthesis nitrogen to grain nitrogen was 12.04%and 16.64%lower,respectively;The nitrogen accumulation after anthesis of high-yield and highefficiency varieties was higher,17.96%lower than that of Low-yield and low-efficiency varieties,and 16.97%lower than that of low-yield and low-efficiency varieties.The nitrogen use efficiency,nitrogen absorption efficiency,aboveground nitrogen accumulation,pre flowering nitrogen transport and post flowering nitrogen accumulation of low nitrogen tolerant varieties were higher than those of low nitrogen sensitive varieties.Under the normal nitrogen level,the nitrogen use efficiency,nitrogen absorption efficiency,nitrogen accumulation at flowering stage,nitrogen accumulation at maturity,nitrogen transport before anthesis and nitrogen accumulation after anthesis of low nitrogen tolerant varieties were 22.96%,24.23%,23.34%,24.23%,24.23%and 23.78%higher than those of low nitrogen sensitive varieties,and 30.15%,28.33%,28.32%,28.34%,29.56%and 28.39%higher than those of low nitrogen level. |
