Identification Of Maize Germplasm Resources Heterosis Groups

The narrower genetic background is the main constraint restricting the maize(Zea mays L.) breeding efforts in China. The complete approach to solve this problem is to enhance and improve the germplasm resource with concrete objectives based on heterotic group and pattern studies. Classifying inbred lines into heterotic groups is an important issue in hybrid maize development. It is not only the basis for utilization of heterosis, but also the foundation for establishing corresponding heterotic patterns to enhance the efficiency of hybrid maize breeding. In this research, simple sequence repeats(SSRs) were assigned to investigate the Heterotic Grouping among 223 germplasm resource, which were representative of various types of inbred lines with and without clear pedigree. The results were as follows:1. Thirty-four SSR primers gave stable amplified band pattern detected one hundred and ten alleles among the 223 inbred lines tested. The average number of alleles per SSR locus was 3.17 with a range from 2 to 5. The variation of umc1035、bnlg2097、umc1593a、umc1137and bnlg2190 were the most abundant;The value of polymorphism information content(PIC)for each SSR locus ranged from 0.35 to 0.75 with an average of 0.59. The variation of umc1137 and umc1015 were the most abundant, then umc1765 was the least. The average Marker Index for each SSR locus was 1.98 with a range from 0.71 to 3.76. The variation of umc1137 was the most abundant, and umc1765 was the least. In general, the three indicators on the analysis of marker polymorphism is not completely consistent.2. The genetic distance was calculated by the Jaccard method, and the overall average was 0.7771 with a range from 0 to 0.9982. Then, the genetic distance matrix from SSR fingerprinting data was import into MEGA software. The clustering analysis was inferred using the Neighbor-Joining method and was conducted in MEGA5. Clustering analysis showed that the 223 inbred lines were classified into six groups, i.e. Tangsipingtou, Lancaster,Luda red cob, PB, Reid and the others. The main results were summarized as follows. The first group is Tangsipingtou, the L1, L33, L65, L69, L75, L95, L96, L98, L102, L103. The second group is Lancaster which includes the L2, L3, L8, L12, L13, L14, L31, L71, L72, L81.The third group is Luda red cob which L5, L44, L47, L76, L77, L78, L82, L87, L88 and L89 were included. The group four which contains the L15, L16, L19, L21, L22, L23, L24, L25,L26, L27. And the group five is PB, the L6, L10, L30, L62, L63, L70, L73, L86, L97 and L99 were included. The last group is Reid which includes the L4, L7, L9, L11, L17, L18, L20,L34, L39, L42 and so on.The result of compartmentalizing was as the same as the fact. And the genetic relationship of inbred lines with complex genetic were determined by SSR marker. Heterotic grouping of inbred lines provided preparation top-quality combination a consultation. Also provided the basis for improving the efficiency of hybrid breeding.