甘蓝杂种致死基因遗传分析与精细定位

Hybrid lethality is a kind of phenomenon which the selfing progenies of two parents grow normally and their hybrid individuals are died before sexual maturity. It is highly important for the researches on species formation, genetics and breeding of animals and plants. The previous studies on hybrid lethality in plants were mainly focused on the interspecific hybrid lethality and the embryo rescue and only a few studies involved in the intraspecific hybrid lethality due to the material rarity. For the studies in species evolution, the intraspecific type is more important than the interspecific one. There are no related reports involved in the intraspecific hybrid lethality in crucifer vegetable crops until now. Recently, we found that the death occurred in the seedlings of hybrids derived from crosses inbred line 1×inbred line 2 before the rosette stage. Seedlings of selfing progenies of two inbred lines grew normally，and so did that of hybrids of above two inbred lines crossing with over 10 other inbred lines, respectively. Thus, based on the genetic evaluation among inbreed lines, we will study the hybrid lethality in cabbage by means of introducing the inbred line 3, which is selected without lethal gene. Two hybrids growing normally will be obtained from the crosses of inbred line 3 and inbred line 1, 2, respectively. The segregation populations in lethality, for example (inbred line 1×inbred line 3)×inbred line 2，will be obtained from the crosses of above hybrids and one of inbred line 1, 2, respectively. The segregation ratio of lethal genotype of seedlings within segregation populations will be analyzed. Mapping of the hybrid lethal genes in cabbage will be carried out based on the segregation populations and bulked segregation analysis (BSA). This study will be helpful for the fine mapping and cloning of the hybrid lethality genes, and also can benefit the researches on genetics and breeding in cabbage.

杂种致死是指双亲自交后代正常但杂交后代在性成熟前死亡的现象，其对物种形成与遗传研究具有重要意义。前人对植物杂种的致死研究主要集中在种间杂种致死及胚挽救等方面，而种内杂种致死虽然对物种进化研究更重要，但因材料稀有而研究较少，且在十字花科蔬菜中未见报道。本课题近年新发现甘蓝自交系1（09-211）与自交系2（09-222）杂交的后代在苗期全部死亡，但它们自交及分别与另外十余个自交系杂交的后代均生长正常。本研究拟在致死基因遗传等效性分析的基础上，利用无致死基因的自交系3与携带致死基因的自交系1、2分别杂交，获得的生长正常杂种再分别与能产生杂种致死的另一个自交系杂交，获得致死性状分离大样本群体用于遗传分析，并利用集团分离分析法（BSA）筛选标记，对杂种致死基因进行初步定位（连锁距离<5cM），为精细定位与图位克隆奠定基础，并为甘蓝遗传育种提供指导。

杂种致死是一种生殖隔离类型，其对物种形成具有重要意义。致死材料的鉴定及遗传分析与基因定位，不仅有助于理解杂种致死的遗传机制，还可以为致死基因的克隆奠定基础。试验利用已鉴定的甘蓝致死自交系09-211、09-222、10-260和其它自交系杂交配制的组合为试材，鉴定携带致死基因的新材料，并对甘蓝杂种致死性状进行了遗传分析与基因初步定位。遗传分析结果表明：11-204和11-176为新的甘蓝致死材料；携带致死基因的5份甘蓝材料可分为两组（09-211与11-204为一组，09-222、10-260与11-176为一组），同组材料间具有遗传等效性，表明甘蓝杂种致死性状是由两个显性基因互补控制的。通过集团分离分析法（BSA）筛选1104对InDel引物与1152对SSR引物，利用JoinMap 4.0软件，将来自09-211的杂种致死基因BoHL1定位在C01染色体末端1.97Mb区段，将来自09-222的杂种致死基因BoHL2定位在C04染色体末端6.65Mb区段。因此，结合遗传分析与基因初步定位结果，可以明确甘蓝杂种致死性状遗传符合双位点DM（Dobzhansky-Muller）模式。本研究的完成为甘蓝杂种致死基因BoHL1和BoHL2的精细定位与克隆奠定了基础。