对家蚕第2隐性赤蚁基因(ch-2)的SSR标记定位及连锁分析

家蚕蚁蚕体色突变之一的第2隐性赤蚁(ch-2)有作为特殊遗传系统的实用价值。采用家蚕正常黑蚁品种P50和第2隐性赤蚁品种k04为亲本组配正反交群体,回交后获得回交群体(k04×P50)×k04和k04×(k04×P50),分别记作BC1F和BC1M,基于雌性家蚕的W与Z染色体不发生交换的特点,用已构建的家蚕SSR分子标记连锁图谱对ch-2基因进行定位和连锁分析。在第18连锁群上的20个多态性标记中共筛选出7个与ch-2基因连锁的SSR标记。根据第18连锁群上已有但不表现多态性的微卫星序列,寻找其所在Scaffold上的其他SSR位点并设计引物,结果找到2个新的多态性SSR标记。BC1F群体中的所有黑蚁个体均表现出与F1(k04×P50)相同的杂合型带型,而所有赤蚁个体带型与亲本k04一致,为纯合型,说明家蚕ch-2基因位于第18连锁群。利用另一个群体BC1M构建了ch-2基因的SSR分子标记遗传连锁图,连锁图的遗传距离为70.7cM,ch-2基因位于69.6 cM处。2个与ch-2最近的SSR标记为S1814和S1819,与ch-2的距离分别为7.9、1.1 cM。

SSR Marker Mapping and Linkage Analysis of ch-2, the Second Recessive Gene of Chocolate Larvae in the Silkworm, Bombyx mori

The second recessive gene of chocolate larvae (ch-2) is one of the body color mutations in newly hatched larvae of the silkworm,Bombyx mori.This mutation has practical values for being used as a specific genetic system.In this research,silkworm variety P50 of which newly hatched larvae have the normal black body color and silkworm variety k04 with the second recessive gene of chocolate larvae (ch-2) were used as parental strains to prepare reciprocal populations.After back-crossing,two back-crossed populations,(k04 × P50) × k04 and k04 × (k04 × P50) ,were obtained and designated as BC1F and BC1M,respectively.Owing to a lack of crossing over between chromosomes Z and W of silkworm females,an already established silkworm SSR molecular marker linkage map was used for mapping and linkage analysis to ch-2 gene.After screening 20 polymorphic markers on the 18th linkage group of Bombyx mori,ch-2 gene was found to link with 7 SSR markers.Based on the existing microsatellite sequences that do not display polymorphism on the 18th linkage group,other SSR sites on the Scaffold were searched and were used for designing primers.As a result,2 new polymorphic SSR markers were obtained.All larvae with black body color in BC1 F population showed the same heterozygous profile with F1(k04 × P50) hybrids,and all larvae with chocolate body color in BC1F showed the same homozygous profile with parental strain k04,demonstrating that silkworm ch-2 gene is located on the 18th linkage group.An SSR molecular marker genetic linkage map was constructed by utilizing the other backcrossed population,BC1M.This linkage map has a genetic distance of 70.7 cM,with ch-2 mapped at 69.6 cM.The genetic distance between ch-2 gene and two nearest SSR markers,S1814 and S1819,is 7.9 cM and 1.1 cM,respectively.