Characterization And Molecular Mapping Of A Novel Dwarf Wheat Germplasm Huaai 01 And Wheat Germplasm Development For Resistaace To Stem Rust Ug99

Wheat, as our food supplement, is closely related to our economic life. Due to world’s most widely growing regions and largest consumer population, wheat production is directly related to the world situation including world peace, stability and prosperity. According to wheat development history after World War II, wheat production mainly depends on variety improvement. The goal of wheat breeding is selecting wheat varieties with high yield, high quality and high resistance to disease and pest. Genetic theory and breeding practices show that development and utilization of specific germplasm is the main factor of breeding achievement. However, dwarf source’s unitary in wheat breeding and commercial varieties susceptible to new stem rust race Ug99, which limit further increase in yield and quality, have threatened worldwide wheat development. Therefore, development and characterization of new wheat germplasm is crucial for the improvement of wheat breeding.In our study, we analysed the genetic characterization of Huaai 01 and mapped its dwarfing gene. Meanwhile, we developed some new wheat gemplasms with stem rust resistance and improved a Canadian wheat cultivar Hoffman’s disease resistance by means of marker-assisted gene pyramiding. The results are described as follows:1 Characterization and molecular mapping of wheat mutant Huaai 011) A seedling growth test was performed to test for sensitivity to GA. Huaai 01 showed no significant response to all levels of GA3 tested for both the first leaf length and coleptile length which indicated the dwarfing gene in Huaai 01 is GA-insensitive.2) Huaai 01 was crossed with three tall varieties, all F1 plant height were intermediate between the two parents, and close to the tall parent. Plant heights in the F2 population of each cross showed a trimodal distribution, with 3 peaks. The χ2 test indicated a 1:2:1 segregation ratio, suggesting that a single gene that is partially recessive controls the dwarf phenotype. The gene was named Rht-B2.3) F1 plant of Huaai 01/Een No.1 were crossed with three varieties contains Rht-B1b. All progeny in the 3 crosses were tall, suggesting that the gene Rht-B2 controlling plant height in Huaai 01 was nonallelic with Rht-B1b in these 3 dwarf varieties.4) Using F2:3 population associated with SSR markers and BSA analysis, the dwarfing gene Rht-B2 in Huaai 01 was located on the long arm of chromosome 4B. The markers Xgwm495 and barc1096 were closely linked to the dwarfing gene at a distance of 3.3 and 2.9 cM, respectively.5) Comparing the relative length of each internode to the plant height in Huaai 01 and its original parents, relative lengths of spike and peduncle of Huaai 01 were longer, but all the other internodes were shorter. This indicated the reduction of Huaai 01 was effected by the reduction of 1st to 4th internode from top to bottom.6) Characterization of plant height components in F2 population shows the length of spike is a qualitative character affected by one gene, and that the length of various internodes are quantitative characters, each having their own independent genetic patterns and controlled by polygenes.7) Results of correlation analysis among plant height, plant height components and yield traits indicated that plant height and its components has positive correlation with grain number per plant and spike numbers; but no significant correlation with grain weight per plant, grain weight per spike and thousand grain weight.2 Wheat germplasm development by marker-assisted gene pyramiding for resistance to Ug991) Three DH populations were produced from the F1 plants of crosses (Hoffman*2/RL6099)//(Hoffman*2/Lang), (AC Cadillac/Lang)//(RWG34/RL5405) and RWG34/RL5405//RL6099 via doubled haploid technology.2) Using MAS and backcross, two stem rust resistance genes Sr35 and Sr36 from wheat line RL6099 and Lang were introduced into a Canadian wheat cultivar Hoffman to improve Hoffman’s resistance to stem rust, especially Ug99 lineage. Ug99 race TTKSK infection result shows the stem rust resistance of improved-Hoffman was significantly increased, especially Hoffman with both Sr35 and Sr36 genes.3) By mean of cross and MAS,F1 plants from two composite crosses (AC Cadillac /Lang)//(RWG34/RL5405) and RWG34/RL5405//RL6099 were obtained. After doubled haploid,18 different Sr genotypes in the DH population were obtained. And 13 of 18 genotypes contain two to four Sr genes. TTKSK infection result shows that all the DH lines with more than three Sr genes confer a high level resistance to immunity.