Identification Of Nitrogen Fertilizer Saving And Related Research Of New Wheat Cultivars/lines In Huanghuai Southern Wheat Region

The decline in the quality of cultivated land and the destruction of the ecological environment caused by excessive application of nitrogen fertilizer have seriously affected China’s food security and ecological security.Different wheat genotypes have different nitrogen absorption and utilization capabilities,and breeding new wheat cultivars with nitrogen-efficient is an important way to improve nitrogen use efficiency.In order to screen wheat cultivars/lines with nitrogen-efficient and provide screening index information to promote the breeding process of breeding wheat cultivars/lines with nitrogen-efficient,,this study evaluate Nitrogen fertilizer saving and related research of new wheat cultivars/lines in Huanghuai southern wheat region using three methods,seedling hydroponics,adult-stage hydroponics and two-year field experiments,and the methods.The correlation analysis,membership function method,cluster analysis,and principal component analysis are used to evaluate the low nitrogen tolerance,and molecular detection are carried with molecular SSR markers linked to the nitrogen-saving QTL.Results of this study will provide theoretical reference and technical support for the selection and breeding of wheat cultivars with nitrogen-efficient.Fifty-one new cultivars/lines included in the regional test of Huanghuai southern wheat region in China in the two consecutive years from 2020 to 2021.The field experiment set two nitrogen treatments of bottom fertilizer only(N-),and bottom fertilizer + topdressing fertilizer(N+).A total of 19 indicators,including growth period such as panicle extraction and flowering period,agronomic traits such as plant height,effective panicle,panicle number,1,000 grain weight,yield,physiological traits such as chlorophyll,grain nitrogen concentration,grain nitrogen accumulation,straw nitrogen concentration,and straw nitrogen accumulation,were investigated in the two consecutive years.Three SSR markers linked to nitrogen use efficiency QTL were used to carry molecular detection.The hydroponic method set up two treatments of normal nitrogen(CK)and low nitrogen(LN),and correlation analysis,membership function method,cluster analysis,and principal component analysis were used to evaluate the low nitrogen tolerance of each cultivar,explore the nitrogen-saving identification method,and establish a wheat screening system.The main research contents and results are as follows:1.Screening index for breeding nitrogen-saving cultivars:(1)Nitrogen-saving index was established according to field yield,and the number of panicle grains,chlorophyll content at the booting stage filling stage were significantly correlated with the nitrogensaving index(P <0.01),the correlation coefficients were 0.569,0.494 and 0.531,respectively,which can be used as index for the preliminary screening of nitrogen-saving cultivars.(2)Under the condition of hydroponics at the seedling stage,the low nitrogen environment changed the plant morphology,and the growth of aboveground part of the plant is inhibited more than that of the roots.A totle of 12 traits,includingthe stem and leaf dry weight,stem and leaf nitrogen concentration,root dry weight,root concentration,total weight,total nitrogen concentration,root nitrogen accumulation,total nitrogen accumulation,total root length,root surface area,total root volume and root tip number.of CK are significantly higher than that of LN,while the root-to-crown ratio and root average diameter are of LN are significantly higher than CK.According to the correlation between total nitrogen accumulation and nitrogen physiological utilization efficiency,three traitsindicators,including stem and leaf dry weight,root dry weight and total weight,were screened as nitrogen use efficiency screening indexes.(3)Nine indicators,such as stem and leaf dry weight,root dry weight,total weight,stem and leaf nitrogen accumulation,root accumulation,total root length,root surface area,root volume,and root tip number,were screened by hydroponic method at the adult stage as nitrogen use efficiency screening indicators,and the comprehensive value of nitrogen efficiency was obtained by using its low nitrogen tolerance coefficient,and 10 nitrogen efficient varieties were screened out according to the cluster analysis results.Taking the D value as the independent variable and the low nitrogen tolerance coefficient of each index as the dependent variable,the regression equation for the evaluation of wheat low nitrogen tolerance was established,and the coefficient of determination of the regression equation was R2 = 0.999(P <0.01),and the comprehensive value of nitrogen efficiency could be effectively predicted according to the key indicators.(4)The detection results of two nitrogen use efficiency QTL-linked SSR markers Xgwm495 and Xgdm88 have a certain correlation with the nitrogen saving index,which can be used for molecular labeling auxiliary selection for the breeding of nitrogenefficient wheat varieties.2.Screening of nitrogen-saving wheat cultivars: eighteen wheat cultivars/lines,including Shanhe 1028,Deyan 1658,Fanyumai 20,Womai 169,Kelin 201,Zhongyu 1686,Fumai 13,Ping’an 918,Yangao 160,Xinnong 162,Xinnong 9799,Fumai 916,Zhengmai 172,Xiansheng 368,Fanmai 26,Fenggong 38 and Fanmai 27 were screened out at seedling stage;Nine cultivars,including Fenggong 38,Fanyumai 20,Zhongyu 1686,Xinong 1125,Fumai 916,Zhengmai 172,Ping’an 918,Guanmai 10 and Fumai 13 were screened at adult stage;Ten cultivars,including Luomai 68,Fumai 701,Zhongyu 1686,Luomai 66,Fanmai 26,Fumai 916,Xuke 10,Zhengmai 172,Fumai 13 and Yikemai 17118 were screened under field test.Four nitrogen-saving cultivars Zhongyu 1686,Fumai 916,Zhengmai 172,and Fumai 13 were screened by all three methods,which provides germplasm resources for the breeding of nitrogen-efficient cultivars.3.Establishment of wheat nitrogen efficient cultivars screening process: comparative analysis of three identification methods,improve the wheat nitrogen saving identification system,that is,the seedling stage is set up normal and low nitrogen environment,combined with molecular marker detection,can quickly and efficiently initially screen out cultivars with high nitrogen accumulation at the seedling stage.The plant form of nitrogen efficient wheat be could selected.At the adult stage through hydroponic screening,and the nitrogen efficient cultivars can be verified by field nitrogen saving index(chlorophyll content can be used as an indicator of field initial screening).4.The effect of nitrogen treatment on quality: nitrogen fertilizer has a greater impact on wheat quality,and topdressing treatment can improve grain protein content,gluten index,water absorption rate,total starch content,P value,W value and IE value of blowing bubble function value,and can also improve starch amylity/ branch ratio,so topdressing treatment can improve wheat quality.Although the indicators such as hardness,sedimentation value,wet gluten content and peak viscosity under the topdressing treatment have changed as a whole,they have not reached a significant level,indicating that these indicators are strongly affected by cultivars and weakly affected by nitrogen fertilizer treatment.In this study,for two consecutive years,the nitrogen-saving properties of 51 new cultivars /lines in in Huanghuai southern wheat region were identified,and two hydroponic screenings at different periods were carried out,and a fast and efficient wheat nitrogensaving identification system was established after different identification methods were analyzed,and four cultivars with nitrogen-saving properties,Zhongyu1686,Zhengmai 172,Fumai 13,and Fumai 916,were screened.At the same time,the effects of different nitrogen fertilizer treatments on quality were analyzed.These results provide nitrogen-saving cultivars,screening indicators and identification methods for nitrogen-saving wheat breeding,which provides technical support for rapid breeding of nitrogen-saving wheat in China.