| China is a large country consuming nitrogen fertilizers,but simultaneously,its using efficiency of nitrogen fertilizers is always lower than that of average level of the world.In the precondition that the total application of nitrogen for wheat is constantly added,the nitrogen use efficiency of wheat must be increased to maintain high yield of wheat.Screening genotype of high-efficiency of nitrogen is the main approach to improve using efficiency of nitrogen fertilizers and lessen environmental pollution.In this study,sixteen wheat cultivars were used as tested materials,the principal component analysis and correlation were conducted to find indexers which can be used to accurately evaluate using efficiency of nitrogen,then cluster was conducted with combination of the indexes and yield traits to screen cultivars with different using efficiency of nitrogen,and physiological and biochemistrical characteristics of the cultivars screened were analyzed for revealing genetic mechanism of accumulation and transportation of nitrogen;QTL was applied by accumulation and transportation of nitrogen of DH population for searching QTL distribution hot spots that can stable expression,which will present references for breeding for wheat cultivars with high using efficiency of nitrogen in the future.The main results of the study are as following: In this study,16 wheat cultivars were used as tested materials and total 14 nitrogen accumulation and translocation related traits,including quantity of pre-flowering nitrogen accumulation,quantity of post-flowering nitrogen transportation accumulation,quantity of leaf nitrogen content in mature period/ quantity of total nitrogen accumulation,quantity of rachilla nitrogen content in mature period/ quantity of total nitrogen accumulation,quantity of kernel nitrogen content in mature period/ quantity of total nitrogen accumulation and so on,were measured.After the indicators with larger coefficient of variation were selected,8 indexes related to using efficiency of nitrogen were identified by the principal component analysis and correlation,they were quantity of post-flowering nitrogen accumulation,quantity of pre-flowering nitrogen transportation,contribution rate of pre-flowering nitrogen transportation,quantity of post-flowering nitrogen transportation,rate of post-flowering nitrogen transportation,contribution rate of post-flowering nitrogen transportation,production efficiency of nitrogen in seeds,production efficiency of dry matters of nitrogen.The 16 wheat cultivars were divided into 3 categories according to cluster analysis by using the 8 indexes and the indexes relevant to yield.The first category has high nitrogen use efficiency,including Jinmai 54 and Jinmai 66,and the third category has loe nitrogen use efficiency,including Jinmai 73 and Taimai 269,while the second category is the intermediate type,including Jinmai 61,Tainong 18.Two varieties were chosen from each category,a total of six varieties,to mensurate activity of nitrogen accumulation and translocation related enzyme.The results showed that the activities of the following substences such as soluble protein,glutamine synthetase,glutamate synthetase,transglutaminase,and aspartate kinase had descending tendency after 7 days of flowering,while proteolytic enzyme showed ascending tendency after 7 days of flowering.The enzyme activities of Jinmai 54 and Tainong 66 were higher than those of Jinmai 73,Taimai 269,Jinmai 61,and Tainong 18 in grain filling stage.Correlation between enzyme activities and using efficiency of nitrogen indexes indicated that the activities of most of the crucial metabolic enzymes in flag leaves of the cultivars tested in the different stages of grain filling stage after flowering had significant or extremely significant genetic positive correlation with the 6 main indexes of using efficiency of nitrogen including production efficiency of nitrogen in seeds,production efficiency of dry matters of nitrogen,quantity of post-flowering nitrogen transportation,efficiency of post-flowering nitrogen transportation,contribution rate of post-flowering nitrogen accumulation in seeds,and had significant or extremely significant phenotype and genetic positive correlation with them but had significant or extremely significant phenotype and genetic negative correlation with the 2 main indexes of absorption and utilization of nitrogen including contribution rate of pre-flowering nitrogen accumulation in seeds,quantity of pre-flowering nitrogen transportation.Additionally,genetic correlational coefficiencies between the activities of most of the crucial metabolic enzymes and the main indexes of using efficiency of nitrogen were higher than phenotypic correlational coefficiencies,which suggested that the traits had excellent genetic correlation.which suggested that the expression of these 6 genes do involved in the accumulation and translocation of nitrogen in wheat.Under two water supply treatments,in different developmental stages after flowering,nitrogen content QTL of different developmental stages of leave,stem,rachilla,kernel and plant were detected by detection of unconditional and conditional QTL,additive QTLs controlling nitrogen content in leaves were respectively 10 and 7 with 5.18%~23.8% contribution rates to phenotypic variation,epistatic QTLs were 18 and 11 with 0.50%~43.76% contribution rates to phenotypic variation.Additive QTLs controlling nitrogen content in stems were respectively 12 and 14 with 6.72%~19.67% contribution rates to phenotypic variation,epistatic QTLs were 19 and 7 with 0.88%~33.63% contribution rates to phenotypic variation.Additive QTLs controlling nitrogen content in rachillae were respectively 5 and 4 with 8.65%~17.56% contribution rates to phenotypic variation,epistatic QTLs were 9 and 9 with 0.81%~38.72% contribution rates to phenotypic variation.Additive QTLs controlling nitrogen content in kernels were respectively 14 and 5 with 6.08%~27.44% contribution rates to phenotypic variation,epistatic QTLs were 9 and 5 with 0.40%~30.34% contribution rates to phenotypic variation.Additive QTLs controlling nitrogen content in plants were respectively 15 and 11 with 6.07% ~ 23.06% contribution rates to phenotypic variation,epistatic QTLs were 11 and 14 with 0.04% ~ 36.46% contribution rates to phenotypic variation.The expression of the QTLs showed specialty on space and time,that is to say,most of the QTLs merely expressed in a specific developmental stage and QTLs constantly expressing the whole grain filling stage were not detected.Many main QTLs controlling nitrogen accumulation quantity were detected in the marking regions of WMC74-Xgwm291-Xgwm410 in the chromosome 5A including Qlnit-3D-2,Qlnit-3D-3,Qlnit-3D-4.Deep probe of these hot spots is meaningful for accurate location and mapping clone in the late stage.Under two water supply treatments,in the different developmental stages after flowering,32 additive QTLs and 23 epistatic QTLs controlling nitrogen transportation with 5.39%~18.47% contribution rates to phenotypic variation were detected.Among them,5 additive QTLs and 2 epistatic QTLs controlling quantity of post-flowering nitrogen accumulation with 5.47%~10.96% and 0.01%~6.31% contribution rates,respectively,to phenotypic variation were detected;3 additive QTLs and 1 epistatic QTL controlling quantity of pre-flowering nitrogen transportation with 12.26% ~ 17.81% and 4.29% contribution rates,respectively,to phenotypic variation were detected;3 additive QTLs and 3 epistatic QTLs controlling rate of pre-flowering contribution of nitrogen accumulation in seed with 9.64%~15.55% and 0.47%~16.13% contribution rates,respectively,to phenotypic variation were detected;2 additive QTLs and 3 epistatic QTLs controlling quantity of post-flowering nitrogen transportation with 5.62%~10.35% and 9.47%~18.79% contribution rates,respectively,to phenotypic variation were detected;1 additive QTL and 2 epistatic QTLs controlling rate of post-flowering nitrogen transportation with 9.66% and 14.75%~24.38% contribution rates,respectively,to phenotypic variation were detected;4 additive QTLs and 1 epistatic QTL controlling rate of post-flowering contribution of nitrogen accumulation in seed with 5.39%~15.55% and 19.96% contribution rates,respectively,to phenotypic variation were detected;3 additive QTLs and 1 epistatic QTL controlling production efficiency of nitrogen in seeds with 7.43%~16.15% and 16.36% contribution rates,respectively,to phenotypic variation were detected;11 additive QTLs and 10 epistatic QTLs controlling production efficiency of dry matters of nitrogen with 5.75%~34.91% and 0.82%~35.22% contribution rates,respectively,to phenotypic variation were detected.Main effect QTLs controlling multi-traits were detected in the marking regions such as Xgwm456-Xgdm8 in the chromosome 3D and P3470.4-P4133 in the chromosome 1B.These QTLs had high contribution rates to phenotypic variation,which should have prospect in MAS breeding. |
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