基于M-C作图鉴定牙鲆不同二倍体的遗传特征

为了分析连锁群上不同位置的微卫星标记对鉴定牙鲆二倍体遗传特征的作用,实验以牙鲆选育基础群体为亲本,选择性腺发育良好的个体制备普通二倍体(ND),减数分裂雌核发育二倍体(MGD-1)、连续两代减数分裂雌核发育二倍体(MGD-2),并利用MGD-1发育达性成熟的雌鱼与同时诱导的性反转伪雄鱼交配制备近交二倍体(MGD1H)。从牙鲆遗传连锁图谱选择均匀分布于24个连锁群的72个微卫星标记,用4个MGD-1家系估计微卫星标记与着丝粒之间的相对距离。在假设无交叉干涉的情况下,17个标记位于着丝粒区域,19个标记位于连锁群中部,36个标记位于远着丝粒区域。分别选择上述区域的微卫星标记鉴定牙鲆4种二倍体的遗传特征。结果显示,4种二倍体的等位基因数(A)和多态信息含量(PIC)在不同区域变化范围较小,ND的A和PIC均为最高,MGD1H则表现为最低。随着标记与着丝粒之间距离的增加,4种二倍体的观测杂合度逐渐升高,纯合度逐渐降低。纯合个体比例在着丝粒区域最高,为8.8%～29.1%;在远着丝粒区域最低,为2.4%～23.2%。其中,MGD-1和MGD-2的变化幅度显著高于其余二倍体。结果表明,选择连锁群上不同位置的微卫星标记对鉴定牙鲆不同二倍体的遗传特征具有显著影响。

Identifying genetic characteristic of different diploids in Japanese flounder based on M-C mapping

The mature spawners selected from Japanese flounder selection and breeding founder were used to produce the normal diploids (ND), meiotic gynogenetic diploids (MGD-1), successive two generation meiotic gynogenetic diploids (MGD-2) and inbred diploid (MGD1H) by crossing mature female from MGD-1 with induced sex reversed male. A set of 72 microsatellite markers distributed evenly on 24 linkage groups were selected from the published genetic linkage maps of Japanese flounder. To estimate microsatellite-centromere map distances, four MGD-1 lines were produced. Under the assumption of complete interference, 17 markers were located in the centromeric region, 36 in the distant region from the centromere and 19 in the intermediate region of linkage groups. The genetic characteristics of four types of diploid in Japanese flounder were identified by these markers. Analysis showed that the number of allele (A) and polymorphism information content (PIC) have limited variation range, in which, the A and PIC of ND were the highest while those of MGD1H were the lowest. In four types of diploid, the observed heterozygosity decreased and homozygosity increased as microsatellite-centromere map distance increased. The highest and lowest percentages of homozygous individuals were found in centromeric region from 8.8% to 29.1% and in telomeric region from 2.4% to 23.2%, respectively. In which, the variation range of MGD-1and MGD-2 were significant higher than that of the rest diploids. Thus, choice of microsatellite markers located on different positions in linkage group have greatly impact on identifying genetic characteristic of different diploids in Japanese flounder.