偏凸-柱穗山羊草双二倍体与普通小麦不同杂种世代的染色体及性状分离特点

为探讨偏凸山羊草－柱穗山羊草双二倍体SDAU18在小麦遗传改良中的利用价值，以SDAU18和普通小麦品种烟农15及其9个杂种世代为材料，分析不同自交和回交世代染色体和性状分离的特点。结果表明，随自交和以烟农15为轮回亲本回交世代的增加，染色体数目逐渐减少，回交比自交能使后代的染色体数目更快趋近普通小麦的42条，至F₅和BC₃F₁代，染色体数目为42的植株已分别达93.9%和92.0%。与自交世代相比，回交后代减数第一分裂中期的花粉母细胞的染色体构型较为简单，回交次数过多不利于外源染色体与普通小麦染色体发生重组，一般应以回交2~3次为宜；随自交和回交世代的增进，杂种的育性提高，至F₃和BC₂F₁代育性基本稳定。在不同杂种世代可分离出具有矮秆、大穗、大粒、对白粉病、条锈病免疫或高抗及外观品质优良的变异类型，以F₃和BC₁F₁代的变异类型最丰富。

Segregations of Chromosome and Trait in Hybrid Generations Derived from Cross between Triticum aestivum and Amphidiploid of Aegilops ventricosa×Aegilops cylindrica

SDAU18 is an amphidiploid derived from the cross between Aegilops ventricosa and Ae. cylindrical, which carries excellent traits from the both parents. Because of the good crossability with common wheat (Triticum aestivum L.), it also acts as a bridge material to transfer objective genes from Ae. ventricosa and Ae. cylindrical to improved wheat cultivarsthrough hybridization. To disclose the chromosome segregation of hybrid progenies derived from common wheat ´ SDAU18 cross, we used a common wheat cultivar Yannong 15 as female parent and recurrent parent to develop hybrid generations F₁, F₂, F₃, F₄, F₅, BC₁F₁, BC₂F₁, BC₃F₁, and BC₁F₂. The mitosis in root tip cells and meiosis in pollen mother cells were observed. Agronomic traits, such as plant height, spike length, spikelet number per spike, grain number per spike, and seed-setting rate were also investigated in BC₁F₁, BC₂F₁, and BC₃F₁ generations. In higher generations of selfing and backcross, the chromosome number gradually decreased and eventually tended to 42, which was the same as common wheat. Backcrossing was able to fasten the process than selfing. In the F₅ and BC₃F₁ generations, plants with 42 chromosomes were accounted for 93.9% and 92.0%, respectively. Chromosome configuration in PMCs MI was simpler in backcross generations than in selfing ones. Compared with the BC₁F₁ and BC₂F₁ generations, BC₃F₁ showed less diversity in chromosome configuration, indicating that excessive backcross resulted in less chromosomes recombination between SDAU18 and common wheat. Two or three rounds of backcross were feasible. With the increasing generation of selfing and backcross, fertility of the hybrid was improved till the stable status in F₃ and BC₂F₁ generations. In various generations, variant plants with excellent traits were found, such as dwarf plant, huge spike, large grain, high resistance or immunity to powdery mildew and stripe rust, and good appearance of grain. In particular, the F₃ and BC₁F₁ generations had the most variation types.