鲢鳙杂种亲本连锁图标记加密和共线性比较

Densification and syntenic comparison of parental linkage maps in interspecific hybrids of silver carp and bighead carp

鲢(Hypophthalmichthys molitrix)与鳙(Aristichthys nobilis)杂种的养殖性能优于亲本,在水产养殖中利用广泛。为促进鲢、鳙遗传资源管理、经济性状定位等研究,已构建了鲢鳙种间杂种亲本的遗传连锁图,但图谱以AFLP标记为主,利用范围有限。为提高图谱质量和可用性,本研究采用新开发的微卫星标记加密了鲢鳙杂种亲本连锁图。雌性亲本鳙的连锁图标记总数从153增加到288(包括新开发微卫星标记93个),雄性亲本鲢的连锁图标记总数从271增加到511(包括新开发微卫星标记136)。鳙图谱总长度从852.0cM增加到965.8cM,鲢图谱总长度从952.2cM增加到1049.6cM。鲢、鳙图谱共线性比较甄别出22个同缘连锁群,标记排列只存在轻微重排现象。亲本间共享的76个微卫星标记界定的标记间隔总长度在亲本间无差异(雌:雄=1:1),与鲢鲢种内杂种亲本共享微卫星标记界定间隔的总长度雌雄比(1:0.45)显著不同。与模拟自然受精(种内杂种)相比,混精受精(种间杂种)可增加雄性亲本基因组范围的重组率。鲢鳙形态相似,染色体组型相同,杂种可育,鲢鳙杂交对重组率没有影响或影响很小。根据研究结果,认为混精授精回避了精子竞争,强化了全基因组重排,不利于新形成的和已有的优良单倍型的保留,是鲢鳙养殖性能退化的原因之一。

Hybrids of silver carp （Hypophthalmichthys molitrix） and bighead carp （Aristichthys nobilis） are widely accepted in aquaculture due to their better culturing performance than their parents.In order to facilitate diverse studies of the two species,such as genetic resource management and mapping of economic traits,we have constructed the parental linkage maps of the interspecific hybrids previously;however,the maps contained mainly AFLPs.In order to increase the quality of the parental maps and their applicability,they were densified with newly developed microsatellite markers in this study.For the bighead carp （female parent） and the silver carp （male parent） map,the number of assigned markers increased from 153 to 288 （including 93 new microsatellites） and from 271 to 511 （including 136 new microsatellites）,respectively.The total length of the female map increased from 852.0 to 965.8 cM,while the total length of the male map increased from 952.2 to 1 049.6 cM.Syntenic comparison between bighead carp map and silver carp maps identified 22 homologous linkage groups,among them slight rearrangement of markers was found.The total length of the common intervals bounded by 76 parentshared microsatellites was almost the same （female：male=1：1）,which was significantly different from that of the intraspecific hybrids of silver carp （female：male=1：0.45 [17]）.In comparison with the mimic natural fertilization （intraspecific hybrids [17]）,the mixed milt fertilization （interspecific hybrids,this study） caused the obvious increase of genome wide recombination rate.The hybridization of silver carp and bighead carp should not influence the recombination rate of either parent;they are morphologically similar to each other and interfertile and have identical karyoptypes.We believe that mixed milt fertilization avoide the competition among sperms of an ejaculation,enhancing genome wide recombination accordingly.This fry raising method is not favorable to the reservation of the elite haplotypes either newly formed or previouly selected,being one of the main reasons causing the depletion of culturing performance of these two species.