Genetic Structure of Melampsora Epitea Populations in Swedish Salix Viminalis Plantations

Amplified fragment length polymorphism (AFLP) was used to study the genetic structure of populations of the willow leaf rust, Melampsora epitea, in Swedish willow plantations. In total, 197 isolates collected from Salix viminalis clones in three locations in Sweden were analysed. AFLP profiles based on 83 markers were used to compute genetic distances between pairs of individuals. High levels of gene and genotypic diversity were detected in all populations, with 96% of the AFLP loci being polymorphic and with normalized Shannon's diversity indices ranging from 0.977 to 1.0. Analysis of molecular variance (AMOVA) showed small significant differences among locations, although most of the molecular variability was found within locations (97.5%). Five isolates from one willow clone in one location differed markedly from the common pattern. When these five exceptional isolates were excluded, no significant differences among willow clones were found with AMOVA. Sexual reproduction and spore migration appear to be important factors for the population genetic structure of this pathogen.     

Population differentiation and genetic variation inform translocation decisions for Liatris scariosa var. novae-angliae, a rare New England grassland perennial

Augmentation of small rare species populations is sometimes suggested on genetic grounds. However, outbreeding depression via dilution of local adaptation or break-up of genomic coadaptation may occur. These effects depend on the causes of population divergence. Here, we compare genetic measures of population divergence in Liatris scariosa var. novae-angliae, a rare New England perennial. We measured G_ST, neutral marker subdivision, and Q_ST, quantitative subdivision of propagule and juvenile plant traits. G_ST was relatively high. Q_ST for leaf shape exceeded G_ST, indicating local adaptation, while Q_ST for other traits fell within or below the G_ST range. Local adaptation appears low for juvenile traits, although the high G_ST cautions against translocation because of potential coadaptation. If translocation is still required, however, donor populations should contain high quantitative genetic diversity. We assess population size and allozyme diversity as predictors of quantitative genetic variation, but find these poor proxies for direct measurement.     

兴义矮脚鸡群体内遗传变异分析

[目的]从分子水平上分析兴义矮脚鸡的选育效果,为矮小型鸡的品种资源保护和开发利用提供理论依据。[方法]采用10个微卫星座位对3个品系贵州兴义矮脚鸡（100日龄）,即黄羽（xy）、麻羽（xs）和黑羽（xb）（各50只）的遗传多样性进行研究。[结果]3品系矮脚鸡在10个微卫星座位上共检测到68个等位基因,各座位上等位基因数为5～10个,平均为6.800个,平均有效等位基因数4.3002。10个微卫星座位的期望杂合度在0.5238～0.8816,平均为0.7326。多态信息含量（PIC）的范围在0.4981～0.8656,平均为0.6973。3品系间的遗传分化系数（Fst）为0.0129～0.0664,平均值为0.0289。各座位的基因流都大于1,平均Nm值为8.4109。3品系矮脚鸡两两之间的遗传距离在0.0464～0.1474之间,xy和xs品系间的遗传距离最小,但两者与xb品系之间的遗传距离均较远。[结论]兴义矮脚鸡各品系间遗传分化较小,均有丰富的遗传多样性,仍有较大的选育空间。     

新铁炮百合自交初代遗传结构与分化的研究

采用等位酶分析技术对新铁炮百合自交初代各株系的遗传学结构与遗传分化进行了初步研究，F－统计量分析结果表明，经过自交与选择，株系遗传纯合度明显增加，FIT值F4较F3增加，达0．72，株系内的变异减少，株系间的分化增加，FST值增大，F4代株系间平均遗传距离较F3代株系有一定增加，加强了株系间的分化。     

江西地方家鹅资源遗传结构及遗传分化研究

利用25对微卫星标记研究了江西4个家鹩资源群体(莲花白鹅、兴国灰鹅、广丰白翎鹅和丰城灰鹅)的遗传结构及遗传分化,通过计算F-统计量、基因分化系数和基因流等参数,评估了各群体间遗传结构与分化.结果表明:4个鹅群体间存在较大的遗传分化,20.7%的遗传变异来自于群体间的差异.就全群而言,基因分化系数(GST)为0.1667.莲花白鹅与兴国灰鹅之间的基因流(Nm=1.1802)最大,广丰白翎鹅与丰城灰鹅的基因流(Nm=0.8577)最小.莲花白鹅与兴国灰鹅Ds遗传距离(0.2036)最近,广丰白翎鹅与兴国灰鹅的DS遗传距离(0.2935)最远.基于DS遗传距离采用NJ聚类法构建系统树,4个家鹅资源被划分为2大类.分析遗传分化与地理距离的相关关系发现,江西地方鹅种的遗传分化与地理距离不存在明显关联.     

Genetic analysis and molecular mapping of two dominant complementary genes determining resistance to sugarcane mosaic virus in maize

Recent work and publications in human population genetics involving very dense SNP datasets suggest that the use of these markers will become common in plant breeding. The experience of human geneticists futher suggests that attention will need to be paid to the very high degree of genomic heterogeneity of population genetic measures such as genetic diversity. Dense marker sets will also allow more precision of estimates of relatedness between individual plants or pure-breeding lines.     

Variation and population structure at microsatellite and isozyme loci in wild cabbage ( Brassica oleracea L.) in Dorset (UK)

We examined variation at four isozyme and seven microsatellite loci in natural populations of Brassica oleracea L. on the coast of Dorset. All loci were polymorphic, and the diversity index of isozyme loci was similar to that of the microsatellites. Both microsatellites and isozymes showed significant spatial differentiation of genetic variation, but the scale differed between the marker types. Significant non-random mating at isozyme loci was detected within small groups of about five plants, in which adjacent individuals were separated by less than 5 m. On the other hand, non-random mating at microsatellite loci was only detected within the Dorset region as a whole. F_ST was significant for all loci and there was evidence of isolation by distance at both microsatellite and isozyme loci. From these data we infer that there is low but significant amounts of gene flow among B. oleracea populations in Dorset. The differences in the genetic structure between the two types of marker may be due to higher mutation rates at the microsatellite loci; however, the data suggest that stepwise gain or loss of single repeat units is not the principal mechanism.