【作者】 魏昕；

【导师】 潘光堂；

【作者基本信息】 四川农业大学 ， 生物化学与分子生物学， 2004， 硕士

【摘要】 本文采用性状表型分析和分子标记研究了控制双亲的混合选择法对MW964群体在四川生态条件下适应性改良效果。结果如下： 1．表型改良结果。经过5轮混合选择后，群体的播种至抽丝日数、播种至散粉日数和雌雄间隔（ASI）有显著的选择增益。群体平均每轮提早抽丝0.71天，提早散粉0.30天，ASI平均每轮缩短0.41天；而播种至成熟、秃尖长、穗粗、穗重、行粒数、轴粗、轴重、子粒深度和群体产量也有显著的相关响应，且多数性状的表型变异系数随着选择世代的增加有所下降。 2．遗传多样性指数。从85对SSR引物中筛选出40对对各轮群体扩增效果好，且有差异的引物。由40对引物计算各群体的遗传多样性指数及变幅范围是，C₀分布在0.5527～2.756，平均为1.891；C₁分布在0～2.643，平均为1.730；C₂分布在0～2.536，平均为1.658；C₃分布在0～2.583，平均为1.608；C₄分布在0～2.438，平均为1.579；C₅分布在0～2.421，平均为1.482；有88.5％遗传多样性分布于群体内，有11.5％分布于群体间。群体内的遗传差异随着选择的增加呈下降趋势。群体内的遗传多样性大于群体间的遗传多样性，说明经混合选择后群体内仍然保持较丰富的遗传变异。 3．群体内遗传距离。根据40对引物计算各轮群体内的平均遗传距离，结果C₂遗传距离最大为0.502，其次C₀遗传距离为0.488，C₁的为0.480，C₃的为0.475，C₄的为0.436，C₅的遗传距离最小为0.423。表明总体而论群体内遗传差异有减小的趋势。 4．基因杂合度比较。40对引物计算的基因杂合度（H），C₀为0.793，C₁为0.781，C₂为0.775，C₃为0.763，C₁为0.752，C₅为0.727，实际选择增益为-0.013，与线性回归响应（-0.012）相一致。从另一侧面表明随着选择轮次的增加群体的遗传变异有减小的趋势。 5．多态位点与多态位点百分率比较。本实验的40对SSR引物共以418个扩增位点计，C₀群体多态位点数为386个，多态位点百分率为88.0％；C₁群体多态位点数为316个，多态位点百分率为75.6％；C₂群体多态位点数为304个，多态位点百分率为72.7％；C₃群体多态位点数为293个，多态位点百分率为70.1％；C₄群体多态位点数为283个，多态位点百分率为67.7％；C₅群体多态位点数为267个，多态位点百分率为63.9％。多态位点数与多态位点百分率都呈依次递减趋势，也说明选择群体的遗传变异逐渐减小。 6．基因型种类及频率比较。统计40对引物扩增各轮群体的基因型种类及频率，并计算其总和，发现原始群体C₀的基因型种类多，为418且频率分布较散，C₁为412，C₂为382，C₃为357，C₁为317，C₅为318，呈依次减小趋势，选择后高代群体C₁、C₅的基因型种类少频率分布集中。这可能是由于连续对开花期性状定向选择的结果，也可能还与群体有效含量和选择强度引起的遗传漂变有关。更多还原

【Abstract】 A -tropical population MW964 was under biparental mass selection for 5 cycles. The object of this selection method was improvement of its adaptability to the local environmental conditions in Sichuan. The research results of phenotype and molecular markers were obtained as follows:1. From phenotype analysis, we can draw a conclusion, after 5 cycle biparental mass selection; the mean days to silking and shed pollen in MW964 were significantly reduced. Per cycle for silking was shortened by 0.71 days, and per cycle for shedding pollen was shortened by 0.30 days. The ASI (anthesis-silking interval) per cycle was shortened by 0.41 days conrespontedly. Significantly correlated responses are found in other traits such as mature period, barrent, ear diameter, ear weight, kernel numbers per row, axis diameter, axis weight, kernel deepness, and yield per population. The phenotype variation coefficients of many traits decreased with the selection.2. The genetic diversity index, this experiment screened 40 pairs’ primers with good extending effect and good diversity from 85 pairs primers. The genetic diversity index was calculated by polymorphism alleles of 40 pairs’ primers. The genetic diversity index of population Co changes from 0.5527 to 2.756, the average is 1.891, and that of Pop.C1 changes from 0 to 2.643, the average is 1.730. That of Pop.C2 changes from 0 to 2.536, the average is 1.658. That of Pop.C3 changes from 0 to 2.583, the average is 1.608. That of PopC4 changes from 0 to 2.438, the average is 1.579. That of Pop.C5 changes from 0 to 2.421, the average is 1.482. 88.5% genetic diversity distributes in intra-population and 11.5% in inter-population. The inter-population’s genetic diversity is more than the intra-population’s and the genetic diversity within populations declined along with the selection process.3. The average genetic distance(GD), the GD of Co, C1, C2, C3, C4, C5 were 0.488, 0.480, 0.502, 0.475, 0.436, 0.423 respectively. Of them, the GD of Pop.C2 was the biggest and that of Pop.C5 was the smallest.4. The genie heterosity of per populations was 0.793(C0), 0.781(Ci), 0.755(C2), 0.763(C3), 0.752(C4), 0.727(C5) respectively. The factual select imprument .(-0.013) was consisted with the line correlate response (-0.012), (R2=0.957). These demonstrate the genetic diversity declined with the selection increasing cycles.375. The number of polymorphic loci and ratio of polymorphic loci. This experiment amplified 418 alleles by 40 pairs SSR primers. The number of polymorphic loci of per populations was 386(C0), 316(Ci), 304(C2), 293(C3), 283(C4), 267(C5) respectively and the ratio of polymorphic loci was 88.0%(C0), 75.6%(Ci), 72.7%(C2), 70.1%(C3), 67.7%(C4), 63.9%(Cs) respectively. They declined along with the selection process.6. The comparation of the genotypes and that of the frequency of genotype. The genotypical numbers of Pop.Co was 418, which was the most but its frequency was dispersed. And that of the Pop d, C2, C3, C4, C5 was 412, 382, 357, 317, 318 respectively. Due to the continuous, oriented selection for the flowering traits and the genetic drift induced by selection intensity or effective population size the genotype of Pop.C4 and Pop.CS were small and the frequencies were concentrated.更多还原