Phenotypic And SSR Classification Of Elite Waxy Maize Inbred Lines

Waxy maize is a special type of maize resources. As the original center, China has plenty of waxy maize germplasm resources. Though waxy maize breeding in China starts comparatively late, it develops at a very fast pace, and has achieved a lot during the past years. However, we still face a series of problems in this field, like unclear division between inbred families, the narrow genetic foundation of the materials used in waxy maize breeding, deficiency of the germplasm utilization and creation. These issues have been the bottleneck problems which limit the further development of the waxy maize breeding in China. Therefore, the diversity study of Chinese waxy maize germplasm, the clarification of their genetic composition, and exploration of the heterotic patterns of the waxy maize germplasm would be of great significance for the effective utilization of the Chinese waxy maize germplasm and the acceleration of the Chinese waxy maize breeding program.15 common inbred lines which represent the heterotic groups in the common maize germplasm in our country and 13 elite waxy maize inbred lines used the waxy maize breeding in Beijing Academy of Agricultural and Forestry Sceience were chosen in the present study to reveal the phenotypic and genetic diversity of the common and waxy maize inbred germplasm in China. The phenotypic diversity of the 28 maize inbred lines was investigated through 47 phenotypic characters in DUS testing; meanwhile, genetic diversity was explored by using 20 SSR loci covering the entire maize genome. And based on genetic diversity, different groups were constructed. The main research achievements were as follows:1. Phenotypic diversity of the 28 maize inbred lines was analyzed via 47 phenotypic characters. For the 15 common maize inbred, there were as many as 142 alleles, which means average alleles per character were 3.0213, ranging from 1 to 5; average effective alleles were 2.2842 per trait, ranging from 1 to 4.0909. The average Shannon-Weaver diversity index was 0.8738, ranging from 0 to 1.5247. For the 13 portions elite waxy maize inbred lines, however, there were 128 alleles, which indicated 2.7234 alleles per trait, ranging from 1 to 5, average effective alleles 2.0295, ranging from 1 to 3.3137. The average Shannon-Weaver diversity index was 0.7432, ranging from 0 to 1.5247. These parameters showed that the common maize inbred lines were somewhat more polymorphic than the waxy on the phenotypic level.2. The 28 maize inbred lines can be assigned into two groups based on the 47 phenotypic traits. Group One included four common maize inbred lines: Huangzaosi, X178, Chang7-2, Jing89, while the other common inbred lines belonged to the second group which had two subgroups. One subgroup consisted of all waxy inbred lines and the other was composed of the rest 11 common inbred lines. Based on the analysis of the 47 phenotypic characters analyzed, it can be concluded that common maize inbred lines and waxy maize inbred lines had a distinct difference on the phenotypic level, especially showed by color related phenotypic traits which were also the main factors determining the clustering analysis. 3. 13 waxy maize inbreds were crossed with each other and the yield performances of all these F1 were evaluated. The results showed that the yield performances of the 4 combinations with the Xiangnuo8 as the female parent and Zinuo3, Bainuo6, Huangnuo6 and Jingnuo5 as the male parents had no significant difference, while the other 5 combinations were on the opposite. So it showed that the potential yield of combinations with the same female parent but different male parents would have a great difference. This also indicated the utilization value varied between different inbred lines.4. 20 SSR loci covered the entire maize genome were used to analyze the genetic diversity of the 28 maize inbred lines. A total of 119 alleles were detected, and the alleles per locus ranged from 2 to 11, averaged 5.95 per locus. The average gene diversity was 0.6679, ranging from 0.2041 to 0.8512; the average PIC was 0.6324, ranging from 0.1833-0.8334. A total of 100 alleles were detected in 15 common maize inbred lines by using 20 SSR primers, the alleles per locus ranged from 2 to 8, averaged 5 per locus. On the other hand, a total of 68 alleles were detected in 13 waxy maize inbred lines by these 20 SSRs, the alleles per locus ranged from 1 to 6, averaged 3.25 per locus. The average allele, gene diversity and PIC detected in common maize inbred lines were much higher than those in waxy maize inbred lines.5. 28 inbred lines were clustered into 6 subgroups as revealed by the distance-based clustering method carried out by PowerMarker, as well as by the model-based procedure of Structure. Among these 6 subgroups, two were constructed by waxy inbreds, and the other four were consisted of Ludahonggu, Tangsipingtou, Lancaster, and P respectively. The result of phelogenetic analysis carried out by both PowerMarker and Structure agreed well with the pedigrees of these germplasm.