The Key Sericultural Laboratory of Agricultural Ministry, Southwest University, Chongqing 400715, China.
J Insect Sci. 2011;11:155. doi: 10.1673/031.011.15501.
To investigate the patterns of nucleotide diversity in domesticated silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) and its wild relative, Chinese wild silkworm, Bombyx mandarina Moore, we sequenced nine nuclear genes. Neutrality test and coalescent simulation for these genes were performed to look at bottleneck intensity and selection signature; linkage disequilibrium (LD) within and between loci was employed to investigate allele association. As a result, B. mori lost 33-49% of nucleotide diversity relative to wild silkworm, which is similar to the loss levels found in major cultivated crops. Diversity of B. mori is significantly lower than that of B. mandarina measured as π(total) (0.01166 vs. 0.1741) or θ(W)(0.01124 vs. 0.02206). Bottleneck intensity of domesticated silkworm is 1.5 (in terms of k = N(b) /d, N(b) -bottleneck population size; d-bottleneck duration) with different durations. Gene DefA showed signature of artificial selection by all analysis methods and might experience strong artificial selection in B. mori during domestication. For nine loci, both curves of LD decay rapidly within 200 bp and drop slowly when distance is > 200 bp, although that of B. mori decays slower than B. mandarina at loci investigated. However, LD could not be estimated at DefA in B. mori and at ER in both silkworms. Elevated LD observed in B. mori may be indicator of selection and demographic events.
为了研究家养蚕（鳞翅目：蚕科）及其野生亲缘种，中国野桑蚕（Bombyx mandarina Moore）的核苷酸多样性模式，我们对 9 个核基因进行了测序。针对这些基因，我们进行了中性检验和合并模拟，以观察瓶颈强度和选择特征；在基因内部和基因之间，我们还进行了连锁不平衡（LD）分析，以研究等位基因的关联性。结果表明，相对于野桑蚕，家蚕丧失了 33-49%的核苷酸多样性，这与主要栽培作物的丧失水平相似。家蚕的多样性明显低于野桑蚕，具体表现为π（总）（0.01166 对 0.1741）或θ（W）（0.01124 对 0.02206）。家养蚕的瓶颈强度为 1.5（以 k = N(b) / d 表示，N(b) -瓶颈种群规模；d -瓶颈持续时间），具有不同的持续时间。DefA 基因通过所有分析方法都显示出人工选择的特征，在驯化过程中，它可能在家蚕中经历了强烈的人工选择。对于 9 个基因座，LD 衰减曲线在 200 bp 以内迅速衰减，而当距离大于 200 bp 时缓慢衰减，尽管在所研究的基因座中，家蚕的衰减速度比野桑蚕慢。然而，在 DefA 基因座中无法在家蚕中估计 LD，而在两个蚕种的 ER 基因座中也无法估计 LD。在家蚕中观察到的升高的 LD 可能是选择和种群事件的指标。
