Brown C, Orford M, Tzamaloukas O, Mavrogenis A P, Miltiadou D
Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, PO Box 50329, Limassol, Cyprus.
Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, PO Box 50329, Limassol, Cyprus Agricultural Research Institute, PO Box 22016, Nicosia, Cyprus.
Vet Rec. 2014;175(24):624. doi: 10.1136/vr.102503. Epub 2014 Oct 3.
Inbreeding in a small population of Chios sheep undergoing intense selection for the PrP gene was assessed 10 years after the beginning of a scrapie resistance selection programme. Inbreeding in this stock, already under selection for production traits, was analysed by using pedigree records containing 10,492 animals from 1968 to 2008, and also by genotyping 192 individuals with a panel of 15 microsatellites. Genetic markers indicated a loss of heterozygosity (FIS over all loci was 0.059) and allelic diversity (mean effective number of alleles was 3.075±0.275). The annual rate of inbreeding increased significantly after the start of the scrapie resistance programme, ΔF=0.005 compared with ΔF=0.001 before 1999, and was subjected to several genetic bottlenecks, mainly due to the low initial frequency of resistant animals. However, the mean individual inbreeding coefficient estimated from the pedigree - in this closed stock resembling the case of a rare breed - stood at the level of 4.5 per cent, five generations after the implementation of selection for the PrP gene. The inbreeding coefficient estimated by genetic markers was 4.37 per cent, implying that such a marker panel could be a useful and cost-effective tool for estimating inbreeding in unrecorded populations.
在一项针对瘙痒病抗性的选择计划开始10年后，对一小群正在接受PrP基因高强度选择的希俄斯岛绵羊的近亲繁殖情况进行了评估。利用1968年至2008年包含10492只动物的系谱记录，以及对192个个体进行15个微卫星面板基因分型，分析了这群已在生产性状方面进行选择的种群的近亲繁殖情况。遗传标记表明杂合性丧失（所有位点的FIS为0.059）和等位基因多样性丧失（平均有效等位基因数为3.075±0.275）。在瘙痒病抗性计划开始后，近亲繁殖的年增长率显著增加，1999年之前ΔF = 0.001，之后ΔF = 0.005，并且经历了几次遗传瓶颈，主要是由于抗性动物的初始频率较低。然而，在实施针对PrP基因的选择五代后，从系谱估计的平均个体近亲繁殖系数——在这个类似于稀有品种的封闭种群中——为4.5%。通过遗传标记估计的近亲繁殖系数为4.37%，这意味着这样的标记面板可能是估计未记录种群近亲繁殖的一种有用且具有成本效益的工具。
