毛白杨杂种三倍体的2n雌配子形成途径鉴定

由于受杨树大孢子母细胞减数分裂不同步性影响，通过施加理化处理诱导杨树大孢子染色体加倍授粉杂交获得的三倍体，可能既包括来源于第一次减数分裂核复原形成的2n雌配子(FDR)，也有来源于第二次减数分裂核复原形成的2n雌配子(SDR)，难以进行表型鉴别，而通过分子标记分析可以实现不同类型2n雌配子的区分。本研究以通过高温诱导毛白杨大孢子染色体加倍所获得的87株三倍体及其亲本为材料，从母本杂合且与父本有差异的SSR多态性引物中，筛选出5对适宜于2n配子诱导途径来源鉴定的重组率较低的SSR分子标记。在此基础上，利用这5对低重组率SSR分子标记，开展毛白杨杂种三倍体的2n雌配子诱导途径来源分析。结果表明，不同毛白杨杂种三倍体的2n雌配子相应简单重复序列区域的等位基因配置不同，利用筛选出的5对低重组率SSR标记可以实现毛白杨杂种三倍体的2n雌配子诱导途径鉴定，其中35株三倍体来源于FDR型2n配子，另52株来源于SDR型2n配子。此外，选用5个位于高重组率位点的SSR引物进行检测分析，结果验证了随机挑选的SSR引物用于鉴别结果是不完全可靠的，只有挑选低重组率的SSR位点才可能准确鉴定2n配子来源。开展毛白杨杂种三倍体的2n配子诱导途径鉴定研究，对于FDR、SDR不同形成途径的2n配子传递亲本杂合性分析，以及毛白杨三倍体育种策略制定等具有重要意义。 

Origin identification of 2n female gamete of Populus tomentosa triploid hybrids

Due to the asynchronism during the process of megaspore mother cell meiosis, triploid poplars which were induced by chromosome doubling of megaspores through physical or chemical treatment could be either derived from the first-division restitution ( FDR) or the second-division restitution ( SDR) . And it is difficult to identify the origin of the obtained triploids through their phenotypes. However, molecular marker analysis provides an efficient way to identify the origin of 2n female gametes. In this study, 87 triploid Populus tomentosa hybrids were induced by chromosome doubling of megaspores through high temperature treatment. Using these 87 triploids and their parents as material, five appropriate primers ( female parent has heterozygous alleles which are different with alleles of male parent ) with low recombination rate were selected to avoid the impact of homologous recombination on identifying the origin of 2n gametes. Based on these five SSR primers, results were shown that relative allele configurations at SSR loci of 2n female gametes in different triploids were inconsistent. Using the selected five SSR markers with low recombination rate, we identified the origin of 2n gametes of P. tomentosa triploid hybrids. It was shown that 35 triploids were originated from FDR 2n gametes, and the other 52 triploids were originated from SDR 2n gametes. Otherwise, five SSR primers with high recombination frequencies were detected and analyzed. The results confirmed that the randomly selected SSR primers used for the identification of origin were not completely reliable, only the SSR loci with low recombination frequencies can be used to identify the origin of 2n gametes accurately. The identification study of the origin of 2n gametes of triploid P. tomentosa is of great importance for the heterozygosity analysis of FDR and SDR 2n gametes, as well as the breeding strategy establishment for triploid P. tomentosa.