| Brassica napus is one of the most important oil crops in China.Lodging is a serious problem which can lead to significant yield loss and difficulty in harvesting.Reducing plant height can improve lodging resistance with favorable dwarf genes.Therefore,mapping and studying on molecule mechanism of dwarf gene have been paid much attention by scientists with targets such as enhancing the lodging resistance and improving crop yield.To study the darf mutant derived from a EMS-mutationized lines M176 in our lab,present works based on previous SNP experiments,have constructed two BC1F2 and a BC1F2:3 family population with large sample size,derived from the dwarf mutant and parent Zhongshuang 11 with normal plant heights.Further,SSR markers were developed on basis of Brassica genome sequences for marker-assisted selection,then fine mapping of the major gene controlling plant height were conducted.Finally,the agronomic traits between the plants with normal and dwarf plant heights within the family populations were investigated for agronomic traits comparisons between the plant height types.The main results are as follows:1.Development of SSR markers:With the help of SSR hunter,101 SSR sites were found,among which 92 new primers were developed according to the Ninth chromosome of BAC.Only six polymorphic markers were found,and they are BrA09K18,BrA09K20,BrA09K22,BrA09K23,BrA09K25 and BrA09K36.2.Fine mapping of the gene controlling plant height:The six specific markers were applied to identifying the genotype.Totally 6120 individuals were analyzed.①In BC1F2-1 with 1866 individuals,25 recombinants were found,and the frequency of recombination between the specific markers and the target gene was estimated to be 0.00%-0.487%;②In BC1F2-2 with 1712 individuals,the recombination frequency between the specific markers and the target gene was 0.00%-0.829%;③In BC1F2:3 with 2542 individuals,the recombination frequency between the specific markers and the target gene was 0.00%-0.536%;④These results demonstrated that the dwarf gene is located on a short interval between BrA09K23 and BrA09K36 on chromosome A9.BrA09K25 was the marker cosegregated with the dwarf trait gene.3.Comparisons of the agronomic traits between the dwarf and normal plants:In BC1F2-1 family population,the plant height of dwarf and normal plant were 101.9±11.2 cm and 150.1±8.1 cm,the branching height of dwarf and normal plant were 10.0±3.1 cm and 52.3±7.9 cm,the number of primary branch of dwarf and normal plant were 10.8±2.2 per plant and 9.4±2.3 per plant,and the 1000-seed weight of dwarf and normal plant were 3.5±0.3 g and 3.7±0.5 g,respectively.Statistical test showed extremely significant difference between dwarf and normal plant in plant height,branching height and number of primary branch,significant difference in 1000-seed weight,and no difference in the length of main inflorescence,siliques per plant and yield per plant.In BC1F2-2 and BC1F2:3-1 family population,the agronomic traits between the dwarf and normal plants were investigated and compared,the results were found identical to those concluded from BC1F2-1 family population.The existence of dwarf locus,not only lead to the decrease of plant height,branching height and 1000-seed weight,but also lead to the increase of number of primary branch and stem diameter.And it has no significant influence on siliques per plant and yield per plant.Therefore,the inheritance and utilization of the dwarf material can enhance the lodging resistance and improve crop yield. |
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