| Wheat is one of the major food crops in the world, and it is the main important raw material for food, fodder and industrial production. With the increasing of global population, the demand of wheat is getting larger and larger. Wheat production improvement has become one of the most important tasks in agricultural production. Nitrogen is an indispensable nutrient element in wheat growth and development; it plays an irreplaceable role in yield formation process. So, a large amount of nitrogen fertilizer is putted on production to improve the yield of wheat and to meet the growing demand for food. But, with the increase of nitrogen fertilizer use, the kind of behavior has caused serious damage to the environment, reduced the nitrogen use efficiency of crop and raised the cost of production. Therefore, how to improve nitrogen use efficiency of wheat and reduce nitrogen fertilizer applies has become an urgent problem which needs to be solved at soon.A large number of studies have shown that that different varieties or lines vary in their ability of nitrogen uptake and use efficiency under nitrogen deficient conditions. The wheat which with high nitrogen use efficiency can grow and develop normally at a relative low nitrogen environment. Obviously, cultivating the wheat cultivars which with high nitrogen efficiency is an important way to improve nitrogen use efficiency; the screening of low nitrogen tolerant wheat germplasm resources is the basis of cultivating wheat varieties with high nitrogen efficiency. At the same time, the positioning of genes which controled nitrogen efficiency related traits has been proved to be another important method to improve the nitrogen use efficiency of wheat. However, N efficiency is a typical quantitative trait, it is controlled by various genes and easily affected by environment and it is difficult to identify the genes with the traditional genetics methods. QTL mapping technology can rapidly and accurately excavate the genes which controled nitrogen use efficiency. Through the study of QTL mapping, we can reveal the genetic control of nitrogen use efficiency of wheat and lay the foundation for wheat nitrogen efficient molecular marker assisted breeding.In this study,171 recombinant inbred lines (RIL) form synthetic hexaploids wheat SHW-L1 and Sichuan wheat varieties chuanmai32, and their parents were used as the research material. Through the field traits in two successive years and setting up normal and low nitrogen stress levels, screening the high nitrogen use efficiency wheat germplasm resources and QTL mapping the genes which controlled the nitrogen efficiency related traits. In order to lay the foundation for the nitrogen efficient molecular marker assisted breeding and the genetic improvement, meanwhile, to provide a reference for the excavation and utilization of high quality resources. The results as follows:(1) As the relative value of 13 nitrogen related traits such as nitrogen content an uptake of straw, grain and the whole plant, the plant nitrogen use efficiency, nitrogen harvest index, nitrogen dry matter production efficiency and plant height for the index system and so on. Through the principal component analysis and system clustering analysis method, we successfully screened 23 strains with high nitrogen use efficiency from 171 lines.12 lines among them were screened in 2013, material number 36,119,210,46,42,150,74,97,50, 132,38 and 39 respectively.13 lines were screened in 2014, material number 65,30,109,144, 171,63,59,166,38,51,223,53 and 146 respectively. And the material number 38 and 59 were detected in two years.(2) This article has detected 98 QTL locis under four kinds of environment. They were on the all wheat 21 chromosomes, including 70 QTL locis which control the 9 nitrogen indexs and 28 QTL locis which control the 4 main agronomic characters. Among them, the effects of 46 QTLs were in the same direction as the performance-enhancing alleles from the synthetic hexaploid wheat SHW-L1, accounting for 46.94% of total QTL number.5 QTL locis were detected in four kinds of environment, ontrolled the tiller number per plant and the effective panicles per plant respectively, and they distributed in the chromosomes of 2A,4 A,5 A(2) and 6 A. At the same time, we detected 26 locis which controlled the same traits and located very closely. They distributed in the chromosomes of 1B, 1D,2A,2D,4A,5A,6A,7A and 7D, and they controlled all traits except the straw nitrogen uptake, the grain nitrogen uptake, the whole plant nitrogen uptake and the dry matter production efficiency. In addition, this study detected 14 QTL locis which had the effectoin of pleiotropism. They distributed in the chromosomes of 1B,2D,3A,3B,3D,4A,4D,5A,5D,6A,7A,7B and 7D. From the numbers of pleiotropism loci, the chromosome of 2D is the most. And from the traits it controlled, the chromosomes of 4A and 5A were the most and each of them controlled 3 quantitative traits. The locis in 4A chromosomes controlled the plant nitrogen utilization efficiency, the nitrogen harvest index and the whole plant nitrogen uptake, and the locis in 5A chromosomes controlled the plant height, tiller number per plant and the effective panicles per plant. |
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