Morphological And Molecular Basis Of The Characteristics Maintaining Of Maize Inbred Lines

Typicality and purity of maize inbred lines is the important fact that affects the quality and yield of maize hybrids, and it is also an important basis of increasing production. How to keep the characteristics and purity of maize inbred lines, which is less researched by predecessors. I expect that this study clears the basis of fixed-strain cycle technology establishing the nursery and provides theoretical basis for the establishment of the maize inbred propagation by analyzing homozygosis on generations of maize inbred and haploid inducer, field character consistency and inbred lines homozygous influence on production.1. The bases on establishment of conservation nursery. It can be concluded that with the increase of the generation of selfing, inbred lines of homozygosis increased and the homozygous progress decreased by using SNP molecular marker technology to detect homozygosis method of the S0 generation to the S3 generation for three different purity materials Chang 7-2, Zheng 58, and LX9801. The degree of field traits of consistency increased with generation of selfing, and the visual traits of it reached 100% in S3 generation. DH homozygosity which can be an approach to facilitate the homozygosis of inbred line and applied in the build of breed-conservation nursery is very high. Nonetheless, it's impossible to reach a homozygosity of 100% and we need to do farther study to find out the reason.2. The generation number for selfing which Inbred line needed to achieve the desired homozygosity. The actual homozygosity of the offspring of inbred lines was significantly correlated with the theoretical homozygosity. The actual value(y) and theoretical value(x) satisfies the linear equation y=0.7971x+19.44, R2=0.8997**, and any inbred line can accord with?n=-3.322×log[(1-P)/(1-X)] to calculate the generation number for selfing. ?n refers to the generation number for selfing, P refers to the theoretical value of the expected actual homozygosity, and X refers to the theoretical value of the actual homozygosity of purification material.3. Traits that the selection of homozygous individual in nursery depends on. On the basis of SSR's detecting the consistency and researching field characters of the strains whose SNP homozygosity is above 99%. The field selection of inbred line is carried out based on the feature of characteristic stability as well as combining with the generation number for selfing. Firstly, observe the characteristics according to groups which are easier to form a steady homozygosis; secondly, among the individual measurement characters, leaf width, the ear length, ear diameter, the number of lateral branches of the first-grade tassel, the number of ear row and the like can be regarded as the second type of characteristics; thirdly, characteristics which are relatively difficult to be steady, such as the ear height or plant height, the number of grains per row, leaf length, should be selected in high-generation inbred lines.4. Yield is influenced by minor genetic differences of inbred lines. Using different homozygosity strains hybridized with each other, we can find that yield of most of its hybrids(F1) yield was higher than that of the parental line, and heterosis is also increasing with the increase of genetic differences. The hybrid 0x0 yield of Chang 7-2, Zheng 58 and LX9801 were increased by 13.07% compared with population of parents on average. Analysis of variance showed that the differences of yield, kernel weight and rows per ear difference between Chang 7-2 and Zheng 58 most combinations of parents and hybrid were not significant. Lx9801 most combinations of parent and hybrid yield and the number of grains were significantly different. And it is concluded that the most important factor affecting the yield is the number of grains, and the second is the grain weight. The yield of hybrid can also be improved by the hybrid of homozygous line, and the mechanism needs further study.5. SNP correlation analysis of three factors of yield and yield of maize inbred lines. Research results, SNPs related to yield were 18, located on chromosomes 3, 7 and 9. SNPs associated with kernel weight were 3, located on chromosomes 1, 3 and 5. SNPs associated with row grains were 43, located on chromosomes 1, 3, 5, 6, 7, 8 and 9, mainly located on chromosome 3, 9 and common SNPs with yield were 9.6. Annotate the important SNP markers. SNP markers of yield, and row grains and kernel weight and related traits are 10 in all, and gene linkage mainly with plant growth and cell proliferation related enzymes. However, the function of genes that linked to SNPs found still needs further research.