Genotypic Differences In High Nitrogen Utilization In Wheat And Their Morphological And Physiological Characteristics

Wheat is one of the most important food crops in the world.Improving the yield and nitrogen recovery and utilization efficiency of wheat is of great significance for ensuring food safety,saving production cost and reducing environmental pollution.There are significant differences between genotypes in wheat yield and nitrogen uptake and utilization,which is influenced by the environment and nitrogen levels.So screening wheat varieties with high nitrogen efficiency and clarifying their morphological and physiological characteristics under the specific environment will provide the theoretical foundation for breeding as well as cultivation regulation of high nitrogen efficient varieties of wheat.Nineteen varieties in the middle and lower reaches of the Yangtze River wheat region and Huanghuai wheat region were selected and used in this study conducting by field experiment in two test points(Xuzhou and Rugao,Jiangsu Province)in three nitrogen levels(0 kg·hm-2,180 kg·hm-2,270 kg·hm-2).The differences of wheat yield and nitrogen efficiency,dry matter and nitrogen accumulation of variation of transportation,morphological and physiological characteristics were studied.The main results are as follows:1.The effects of genotype and environment interaction on yield and nitrogen recovery and utilization of wheat were studied.Wheat yield and nitrogen efficiency were different among different cultivars.Under two nitrogen levels Huaimai 30 and Yangmai 16 showed high yield and nitrogen efficiency varieties,and have strong adaptability to the environment.The genotype effect was the main factor that affected the yield and nitrogen efficiency of wheat,followed by nitrogen fertilizer effect and genotype environment interaction effect.and the environmental effect was the least.Increasing nitrogen application significantly increased the yield of wheat,but decreased the nitrogen efficiency,and different varieties had different response to nitrogen fertilizer.Cluster analysis showed that in Xuzhou.Aikang 58,Huaimai 30 and Yangmai 16 are high nitrogen efficiency;in Rugao,Huaimai 30,Yangmai 16 and Huaimai 33 are nitrogen efficient varieties.2.The differences of accumulation and translocation of dry matter and nitrogen in wheat with different nitrogen efficiency were studied.With the increasing amount of nitrogen fertilizer,accumulation of dry matter and nitrogen,pre-anthesis translocation amount(PTA),eontribution of pre-anthesis accumulation to grains(CPA),nitrogen translocation amount(NTA),contribution of pre-anthesis nitrogen translocation to grains(CTG)significantly increased while pre-anthesis anthesis ratio(PTR),contribution of pre-anthesis translocation to grains(CPT),nitrogen translocation rate(NTR)decreased significantly,but the change ranges were different among varieties.Comparing with medium and low nitrogen efficiency cultivars,high nitrogen efficient genotypes showed higher CPA,NTA,NTG,NTR,and higher dry matter accumulation from anthesis to mature stage and nitrogen accumulation from jointing stage to anthesis.Correlation analysis showed that the yield was significantly positively correlated with the amount of dry matter accumulation from emergency to jointing stage and anthesis to maturity as well as CPA,while negatively correlated with the amount of dry matter accumulation from jointing to flowering stage as well as PTA.Nitrogen efficiency of wheat correlated positively to nitrogen accumulation amount from emergence to jointing stage and jointing to anthesis stage,NTA,NTR and CTG3.The differences of agronomic characters and carbon and nitrogen metabolism of wheat with different nitrogen efficiency were studied.Spike number and harvest index(HI)were higher in Xuzhou while grain number,plant height,spike length,leaf area index(LAI)and leaf area were higher in Rugao.In N180,compared to medium and low nitrogen efficiency cultivars,high nitrogen efficiency varieties have higher 1000 grain weight,HI,LAI,flag leaf area,nitrogen concent in flag leaf at anthesis,SPAD and net photosynthetic rate,soluble sugar and sucrose content,free amino acid content,NR and GS activity,lower plant height and nitrogen content in flag leaf at maturity.varieties with high nitrogen efficiency showed higher 1000-grain mass,flag leaf area,nitrogen content and SPAD and lower plant height and flag leaf nitrogen content in comparison to the other two nitrogen efficiency varieties.There was no significant difference in HI,NHI and LAI.Correlation analysis showed that in N180,1000-grain mass,HI and NHI,LAI,flag leaf area,net photosynthetic rate,NR and GS in leaves of flowering stage,chlorophyll content(SPAD),soluble sugar and sucrose content,free amino acid content,leaf nitrogen content of flowering stage and nitrogen efficiency showed significantly positive correlation,while the strains height,leaf nitrogen content and nitrogen efficiency showed negative correlation;In N270,1000-grain mass,flag leaf area and main physiological index showed significantly positive correlation with nitrogen efficiency while plant height,flag leaf nitrogen content and nitrogen efficiency showed opposite correlation.In summary,there were significant differences in the yield and nitrogen efficiency of wheat with different genotype,and variety of high efficient use of nitrogen did exist.Huaimai 30 and Yangmai 16 are high yield and nitrogen efficiency varieties with extensive adaptability.The varieties with high nitrogen efficiency have higher yield,grain weight,HI,leaf area,SPAD,LAI,nitrogen content in leaf at anthesis,and lower plant height and leaf nitrogen content.These morphological and physiological indices can be regulated and controlled through genetic improvement and cultivation measures,and should be paid more attention to in the breeding and cultivation of varieties with high nitrogen efficiency.