An Analysis Of SSR Locus Genetic Segregation Of A Double-cross F₁ Population And Molecular Marker-assisted Selection Of Quality Gene Pyramiding In Maize

A large proportion of endosperm protein in maize consist of storage proteins and are deficient of some essential amino acids, particularlly lysine and tryptophan. Thus, maize, a staple crop for food and feed in the world., is inferior of nutrient quality for monogastric animals and man. Protein supplementation to correct such deficiencies is costly and wasteful of energy in animal nutrition ,and is not feasible for most developing countries, which rely on cereal for human consumption. Therefore, the effective way for the improvement of nutritional quality in maize is genetically increasing the amounts of essential amino acids of endosperm protein.Using molecular marker-assisted selection technology, this paper carries out gene pyramiding which deal with two and three genes combined with seclection of lysine content analysis on the base of constructing backcross populations BC₁F₁, BC₂F₁ and double-cross F₁, F₂ populations respectively.23 plants with o2o2O16o16 genotype from double-cross F₁ population are analysed of SSR locus Genetic Segregation. Simple analysis of correlation for the genetic background obtained from different markers number and partial linear analysis of correlation for the recovery rate between Chromosomes and genome are completed in the course of backcross selection to BC₁F₁ population.All of above analysis, the results are as follows:1. From analysis of SSR Genetic Segregation of a Double-cross F₁ Population, we discover that SSR locus and genotypes segregation mainly lean to two high lysine content parents. There are four normal genotypes and three abnormal genotypes during genotypes segregation. Four genotypes have a extremely significant segregation distortion at 13 SSR locus.2. We get 28 plants with o2o2O16o16 genotype and harvest BC₂F₂ seeds by the selection to BC₁F₁ and BC₂F₁ generations. Combined with the recovery rates of genetic background and lysine content analysis, The qualified plants whose recovery rates reach to 95.06% are obtained and further detected, the results indicate that lysine content of BC₂F₂ generation seeds averaged at 0.496%.3. In the background selection to BC₁F₁ population, we find that it is not more accurate to screening the whole genome than ensuring a certain marker number for the recovery rates. At the same time, the results from partial linear analysis of correlation between chromosomes and genome show that the recovery rate from chromosome 4 and 9 manifests negative correlation at the 0.05 significance level and other chromosome such as chromosome 1, 2,7 and so on show positive correlation at the 0.05 or 0.01 significance level4. By the selection to two generationas of double-cross F₁, F₂ population, we finished the pyramiding of o2, o16, wx genes and gain F₃ generation seeds. The lysine content from the final qualified seeds, increased by 29.27% and 30.72% than Taixi 19 and QCL3021 parents respectively, reach 0.583%...