Genetic diversity decreases as population density declines: Implications of temporal variation in mitochondrial haplotype frequencies in a natural population of Tscherskia triton

Although the spatial genetic differentiation that occurs in animal populations has been extensively studied, information on temporal variations in genetic structure and diversity is still lacking, especially for animals with oscillating populations. In the present study, we used the mtDNA D‐loop sequence to assess the temporal genetic variation in samples from six successive years for the greater long‐tailed hamster, Tscherskia triton. Sampling was carried out between 1998 and 2003 in cropland on the North China Plain, China. A total of 108 individuals were analyzed. The temporal samples showed a high level of genetic diversity. Substantial genetic changes in haplotype frequencies over time were detected for the hamster population. Random genetic drift and migration are likely to be the major factors responsible for the observed temporal pattern. The genetic diversity of the hamster population was higher in years with higher population density, and lower in years with lower population density. The result supports our hypothesis that genetic diversity decreases when population density declines in animals whose population oscillates greatly between years. The combined effects of inbreeding and genetic drift caused by reproduction, dispersal and population size might play important roles in the observed changes in genetic structure and diversity between years.     

Dynamics of Protein 27 of Avian Leukosis Virus and Transforming Growth Factor β2 in Lymphoid Leukosis Susceptible and Resistant Broiler Chicken Breeding Stock

The dynamics of the serum concentration of protein 27 (P27) of avian leukosis virus and transforming growth factor ₂ (TGF-₂) were compared during the period between 29 and 59 weeks of age in two flocks of broiler chicken breeding stock undergoing outbreaks of severe lymphoid leukosis (LL) associated with persistent high mortality (susceptible) and in another two flocks of breeding stock with the presence of avian leukosis virus in association with low mortality due to LL (resistant). The average mean concentration of serum P27 in the LL-susceptible flocks was significantly higher (<0.05) than that in the LL-resistant flocks in six out of seven samplings performed at 5-week intervals, between 29 and 59 weeks of age. The peak in the average rise of serum P27 in the LL-resistant flocks (309 pg/ml) was associated with the highest level of TGF-₂ (1282 pg/ml) among all flocks and at all sampling times. The significance of TGF-₂ in inhibition of lymphoid tumour development is discussed.     

Genetic parameters estimates for ewes’ behavioural reactivity towards their litter after lambing

In livestock, improving maternal reactivity towards the litter is an important issue in breeding strategies to promote production and animal welfare. As of yet, no studies have investigated the within-breed genetic variation of maternal reactivity in sheep. The objective of this study was to estimate the genetic parameters of maternal reactivity traits. A total of 1,095 primiparous and 1,441 multiparous Romane ewes were phenotyped 24 hr postlambing using a behavioural test (arena test, AT) over a 10-year experimental period. The test consisted of three successive phases evaluating the ewe's attraction to her litter, reactivity to separation from her litter, and reactivity to a conflict between attraction to her litter and avoidance of a motionless human. The ewes were reared exclusively on rangelands (South of France) and lambed outdoors in the spring. High-pitched bleating and low-pitched bleating in the AT were mostly highly heritable (0.39‒0.46). Heritabilities were moderate for proximity to the litter in the presence of a human (0.27) and low for locomotion and vigilance in the AT (0.09‒0.15). The measurements of a given behaviour in the three phases of the AT were highly genetically correlated. Few genetic correlations were found between the different behavioural traits in the AT, the highest correlations being between high-pitched bleating and low-pitched bleating (−0.43 to −0.77). In conclusion, our findings demonstrate moderate-to-high heritability for maternal reactivity traits. These traits could be included in genetic selection schemes to enhance maternal attachment provided there is no unfavourable link with other production traits.     

Canine fertility: The consequences of selection for special traits

Pedigree dogs and cats are bred aiming to conform breed standards with very poor consideration for breeding stock fertility. At the same time, the genetic asset underlining reproductive traits could be effectively analysed like in other species under selection. The definition of selection targets is very important in breeding protocols determination. The aim of the present work is to present an overview of the different correlations between reproduction and genetics, starting from selection procedure and inbreeding coefficient moving to genomic and the application of SNPs and GWAS on population study and identification of genes involved in phenotypical variation of reproductive traits in dogs. Particular relevance has been given to the concept of inbreeding which effects on canine reproduction have been presented. The use of genomic information in inbreeding coefficient calculation can be considered an improved effective procedure in the evaluation of the genetic variability loss in canine population and its negative effects on reproductive traits.     

不同生长模型估计籽鹅早期体重发育规律及遗传参数

运用Logistic,Gompertz,VonBertalanfy和Cubic4种非线性生长模型对籽鹅1～1周龄的平均体重进行拟合,并分析生长发育规律及遗传参数。结果表明:虽然4个模型都能描述籽鹅的生长过程,拟合度均超过额0.99;但Logistic模型更符合实际饲养情况,能更好地预测体重,为最佳模型,其相应的体重极限参数A为2267.63g,调节参数B为16.27,瞬时相对生长率C为0.47,生长的拐点时间为6.48周龄,拐点体重为1136.81g。     

大白猪繁殖性状遗传参数估计及影响因素的效应分析

本研究对7 945窝大白母猪妊娠周期、总产仔数、产活仔数、健仔数、弱仔数、畸形数、死仔数、木乃伊及死胎数9个繁殖性状进行了最小二乘分析,分析了胎次、配种季节及妊娠周期分类对母猪繁殖性能的影响;并利用动物模型REML(约束最大似然)方法估计动物繁殖性状的遗传力及性状之间的遗传相关.结果表明,胎次对畸形数(P=0.2619)和木乃伊(P=0.4639)影响不显著(P >0.05),对其他7个繁殖性状影响极显著(P <0.01);配种季节对妊娠周期、产活仔数、弱仔数、木乃伊、死仔数及健仔数影响极显著(P <0.01),对畸形数(P=0.3993)影响不显著(P> 0.05),对总产仔数和死胎数影响显著(P <0.05).妊娠周期对木乃伊影响显著(P <0.05),对其他7个性状影响极显著(P <0.01).妊娠周期遗传力最高,为0.34,其他繁殖性状遗传力都低于0.2,为低遗传力性状.总产仔数与妊娠周期之间存在负遗传相关(r_g=-0.10),与产活仔数及健仔数之间存在较强的正遗传相关,遗传相关都超过0.80.妊娠周期与其他繁殖性状之间的遗传相关较小,最高的为妊娠周期与畸形数之间的遗传相关为-0.17.由此得出结论,妊娠周期属于中等遗传力性状,妊娠周期不仅受到胎次、季节等环境因素的影响,而且也受总产仔数等繁殖性状的影响,妊娠周期可作为养猪生产的间接指标.     

农杆菌介导的朝鲜碱茅PuP5CS基因转化紫花苜蓿的研究

为提高紫花苜蓿(Medicago sativa)的抗逆性,利用在朝鲜碱茅(Puccinellia chinampoensis)已克隆的Pu P5CS基因成功构建了p CAMBIA3300-Pu P5CS表达载体,以子叶为外植体,通过农杆菌介导共培养法转化紫花苜蓿"公农5号"(M.sativa cv.Gongnong No.5),并以2.0 mg·L-1的草铵膦进行筛选,抗性愈伤组织诱导率为22.4%,经草铵膦筛选的植株进行PCR检测和RT-PCR检测。结果显示,共获得11株转化植株,表明Pu P5CS基因已转入T0紫花苜蓿植株,且能够在RNA水平上正常表达。     

西北地区和尚头小麦遗传多样性及农艺性状的关联分析

为了解西北地区和尚头小麦种质资源的遗传特性及主要农艺性状特征,采用43份不同来源的和尚头小麦种质材料,在均匀分布于小麦21条染色体上的150个SSR(simple sequence repeats)位点上检测遗传多样性,同时对19个农艺性状在两个试验点进行表型鉴定,并采用GLM(general linear model)模型进行分子标记与表型性状的关联分析。结果表明,19个农艺性状中数量性状遗传多样性明显高于质量性状,除壳色外,其他性状之间均存在不同程度的相关性。利用45对具有多态性的SSR标记共检测出151个等位变异,各标记等位位点变化范围为2～6,平均为3.36个,PIC(polymorphism information content)值变异范围为0.044～0.771。群体遗传结构分析将43份材料划分为8个亚群。关联分析发现11个SSR标记与农艺性状显著关联,单个标记对表型变异的解释率为8.89%～24.74%,这些标记可为特色小麦分子标记辅助选择育种提供理论参考。     

基于遗传多样性评估燕麦品种的农艺性状

为客观评价燕麦种质资源重要农艺性状的遗传多样性,并为黑龙江地区燕麦新品种选育提供关键数据,对51份燕麦种质资源13个农艺性状进行了形态多样性指数分析,并对其中的9个数量性状进行了聚类分析和主成分分析。结果表明,各性状的遗传多样性指数均较大,遗传多样性指数最高的是主穗长(1.517),其次为株高(1.448)和主穗粒重(1.414),性状变异系数最大的是主穗小穗数(34.8%),其次为主穗粒重(33.1%)和单株分蘖数(27.4%);聚类分析将51份燕麦品种的9个数量性状分为4大类群,类群Ⅰ为有益性状不明显,为多目标性状育种的亲本材料,类群Ⅱ为选育矮秆育种目标亲本材料,类群Ⅲ为高杆、增加分蘖数育种目标亲本材料,类群Ⅳ为选育大粒型、多轮层数、多小穗数等育种目标亲本材料。主成分分析结果表明,前3个主成分对变异的累计贡献率为70.09%,第一主成分反映种子产量,第二主成反映单株分蘖数,第三主成分反映株高。     

基于SRAP分子标记构建的菊苣遗传连锁图谱

基于SRAP标记,以遗传关系和表型差异大的菊苣亲本PI 651947和PI 652007杂交获得的84个F₁单株为作图群体,进行连锁图谱的构建。采用Map Manager QTX b20软件进行连锁分析,分别构建了PI 651947和PI 652007的分子连锁框架图,共获得77个SRAP标记,其中父本遗传图谱涉及4个连锁群,包含19个标记,图谱总长为450.9 cM,标记间平均图距为23.7 cM。母本遗传图谱涉及13个连锁群,包含58个标记,图谱总长为1404.8 cM,标记间平均图距为24.2 cM。研究结果可为菊苣重要农艺性状QTL定位奠定基础,为菊苣分子育种研究提供了基础信息。