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文章辩证地分析了猪轮回杂交的利与弊。作者指出：畜禽经济杂交在实践中应用的各类方法都有其适用范围和局限性。只要掌握了杂种优势的基本原理以及获得杂种优势的方法,就能在生产实践中扬长避短,将轮回杂交的缺点降到最低,并将其优点发挥到极致。 相似文献
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对淮南麻黄鸡8只公鸡与62只母鸡交配所得子一代进行外貌鉴定。结果表明,羽色基因纯合程度很低,杂色羽率高达33.63%。白耳率为8.33%。喙、脚色基因纯合程度较高,杂色喙率和杂色脚率分别只有3.57和2.38%。来自边远农村与来自近郊农村的亲本后代外貌性状分离比率差异不显著(P>0.05)。提纯选择的子一代自群繁育所得子二代,其杂色羽率、白耳率、杂色喙率和杂色脚率分别降低到25.25、0.00、2.97和1.98%。子一代和子二代的鸡冠形状均未出现分离现象,显示出这个性状基因纯合程度很高。 相似文献
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I. lvarez L.J. Royo J.P. Gutirrez I. Fernndez J.J. Arranz F. Goyache 《Livestock Science》2008,115(1):80-88
Preservation of rare genetic stocks requires continual monitoring of populations to avoid losses of genetic variability. Genetic variability can be described using genealogical and molecular parameters characterizing variation in allelic frequencies over time and providing interesting information on differentiation that occurred after the foundation of a conservation program. Here we analyze the pedigree of the rare Xalda sheep breed (1851 individuals) and the polymorphism of 14 microsatellites in 239 Xalda individuals. Individuals were assigned to a base population (BP) or 4 different cohorts (from C1 to C4) according to their pedigree information. Genetic parameters were computed at a genealogical and molecular level, namely inbreeding (F), observed (Ho) and expected (He) heterozygosity, individual coancestry coefficients (f and fm), average relatedness (AR), mean molecular kinship (Mk), average number of allele per locus (A), effective number of ancestors (fa), effective population size (Ne and Ne(m)) and founder genome equivalents (Ng and Ng(m)). In general, the computed parameters increased with pedigree depth from BP to C4, especially for the genealogical information and molecular coancestry-based parameters (fm, Mk and Ng(m)). However, Ho and He showed the highest values for C1 and the molecular heterozygote deficiency within population (FIS(m)) showed the lowest value for C1, thus indicating that loss of genetic variability occurs very soon after the implementation of conservation strategies. Although no genealogical or molecular parameters are sufficient by themselves for monitoring populations at the beginning of a conservation program, our data suggests that coancestry-based parameters may be better criteria than those of inbreeding or homozygosity because of the rapid and strong correlation established between f and f(m). However, the obtaining of molecular information in well-established conservation programs could not be justified, at least in economic terms. 相似文献
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国家大豆区域试验品种(系) SSR位点纯合度分析 总被引：5，自引：0，他引：5
利用30对SSR引物,检测2005—2009年参加国家区域试验的1 068份大豆品种(系)的位点纯合度。每年区试品种(系)的平均纯合度为94.9%~97.6%,纯合度高于85%和90%的品种(系)所占比例分别为95%和91.4%,纯合度低于85%的品种(系)有42份(占3.93%),主要为北方春大豆和黄淮夏大豆。位点纯合度低于85%的参试品种(系)的产量比较表明,只有11份品种(系)比对照增产5%以上,20份比对照减产0.04%~13.08%;与纯合度为100%的材料比较发现,位点纯合度较低的材料在区试中产量也较低。建议国家区试品种(系)纯合度标准不低于90%,以保证审定品种的特征特性,为大豆新品种的持续推广利用提供科技支撑。 相似文献
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Genetic diversity loss due to selection for scrapie resistance in the rare Spanish Xalda sheep breed
I. lvarez L.J. Royo J.P. Gutirrez I. Fernndez J.J. Arranz F. Goyache 《Livestock Science》2007,111(3):204-212
The effect of selection for scrapie resistance on genetic variability in the rare Xalda sheep breed was studied. Pedigree information comprised 1851 animals (1444 alive) at the moment of sampling. A total of 304 reproductive (or selected for reproduction) Xalda individuals were sampled and genotyped for 14 microsatellites. Genetic variability was assessed using: gene diversity (1 − average kinship, GD), mean average relatedness (AR) and self-coancestry (ci) at the genealogical level; and expected heterozygosity (He), molecular mean kinship (Mk), molecular self-coancestry (si) and rarefacted average number of alleles per locus (A) at the molecular level. Two breeding strategies were evaluated: a) use of only young rams with genotype ARR/ARR and young ewes with low to moderate risk (risk groups R1 to R3); b) breeding without selection for PrP genotypes. The major cause of losses of genetic variability in the Xalda breed is the drift that occurs when a new group of reproductive individuals is selected. The loss of genetic variability is small in females compared to the males, where it is considerable. However, losses at the molecular level for young females with respect to adult females were above 5%. Young male individuals also retained most of the genetic variability assessed in adult rams. Selection against susceptibility to scrapie produced additional losses of more than 2% for He and A when rYF individuals are considered. As regards males, the situation becomes critical because of the scant number of available ARR/ARR young rams. The consequences for the management of the Xalda breed are discussed. 相似文献
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