| Maize is one of the three major food crops in china,taking an overview of the tremedous achievements of maize breeding and production in China,the use of the key inbred lines play a vital role,not only to cultivate many large-scale promotion of species by using the key inbred lines directly, but also derivatives many widely applicational inbred line breeding material,but the establishment of an Inbred Lines requires a lot of years.In order to speed up the breeding process,it's most important to analysis the process of the formation of maize inbred lines in the molecular level and research the laws of genetic transmission of it.Nitrate reductase gene plays an important role in nitrogen metabolism in plant.Studing on the law of mutation of nitrate reductase gene(NR) in key inbred lines would provide theoretical basis to studying on the gene transfer law of the key corn inbred lines in China, establishment of early prediction of the system and finding that inbred lines which with good potential.In this study,50 key inbred lines were used as research materials,including the four key inbred lines:Huangzaosi,Mo17,Dan 340,478;28 materials of Huangzaosi derivative lines,15 materrials of Mo17 derivative lines,since the key inbred lines of three potential inbred:21-ES,18-599,08-641, through the determination of NR gene coding region sequence,analyze the NR gene sequence, structural characteristics and genetic mechanism of the 50 varieties,combined with the agronomic traits, inferred the genetic relationship between them.The results were summarized as follows:1.In this study,the sequence analysis on the four founder parent inbred lines,18-599,08-641 and 21-ES shows that the sequence of 18-599,08-641,21-ES are highly similar to each other,and the Similarity of sequence between four founder parents and 18-599,08-641,21-ES is MO 17＞Huangzaosi＞478&Dan340. The analysis also found that the mutation of the seven materials occurred inintron 1,2,3 and exon 3,4. The NR gene in Dan 340,478 and the NR gene in Maize are highly gene homologous.less mutations, and Huangzaosi followed,1 in the first intron of multiplethe NR gene mutations occured in the first intron only.But 18-599,08-641,21-ES and Mo17,the mutations in the NR gene occurred in many sites. it showed the same mutation in the law.2.NR gene mutations occurred mainly in Mo17,He344,Qi 302,K14,Guan 17 and 477 in the Mo17 lines and its derived inbred lines.There shows various mutations of the same law in six materials.Most mutations are in intron area,and the types of mutations are insertied mutations,deletion and mutations of single base.The same mutations is occurred of the NR gene in six materials,18-599,08-641 and 21-ES.3.The NR gene mutations mainly occurred except the first intron in Huangzaosi and itsn derived inbred lines.Huangzaosi,H21,⑦61,Wenhuang31413,qi401,Yuanfuhuang,Baiyesi,Huangyesi, ingqihuang,Tianyasi,Ji444,Ji853,Kanghuang4,Jing404,Jing7,Huangzaosi -15,Jing24 are the major mutation of the material,which showed the same mutation in the law and consistented with the performance of 18-599,08-641,21-ES in the first intron.4.From the agronomic level,the cluster analysis found that18-599,08-641,21-ES and Mo17 gathered for a class,Huangzaosi,Dan 340 and 478 gathered for a class,The results are the same as the study on the molecular level dose;in the cluster analysis on 18-599,21-ES,08-641,Mo17 and its derived inbred lines,all materials are classed into two groups,18-599,21-ES,08-641,Nan 23232, Nongda 178 and Mo17 were classified in the same group,Mo17 and its derived inbred lines were classified into another group.Nongda178,18-599,21-ES and 08-641 in one group,other research results are basically the same as the molecular level;in the cluster analysis on 18-599,21-ES, 08-641,Huangzaosi and its derived inbred lines,all materials were classified into two groups,18-599, 21-ES,08-641 and K12 were classified in the same group,Huangzaosi and its derived inbred lines were classified into another group.K12 cluster results are inconsistent with the molecular level,other results are basically consistent with the molecular level.
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