Effects of breed proportion and components of heterosis for semen traits in a composite cattle breed

The aim of this study was to estimate the non‐additive genetic effects of the dominance component of heterosis as well as epistatic loss on semen traits in admixed Swiss Fleckvieh, a composite of Simmental (SI) and Red Holstein Friesian (RHF) cattle. Heterosis is the additional gain in productivity or fitness of cross‐bred progeny over the mid‐purebred parental populations. Intralocus gene interaction usually has a positive effect, while epistatic loss generally reduces productivity or fitness due to lack of evolutionarily established interactions of genes from different breeds. Genotypic data on 38,205 SNP of 818 admixed, as well as 148 RHF and 213 SI bulls as the parental breeds were used to predict breed origin of alleles. The genomewide locus‐specific breed ancestries of individuals were used to calculate effects of breed difference as well as the dominance component of heterosis, while proxies for two definitions of epistatic loss were derived from 100,000 random pairs of loci. The average Holstein Friesian ancestry in admixed bulls was estimated 0.82. Results of fitting different linear mixed models showed including the dominance component of heterosis considerably improved the model adequacy for three of the four traits. Inclusion of epistatic loss increased the accuracy of the models only for our new definition of the epistatic effect for two traits, while the other definition was so highly correlated with the dominance component that statistical separation was impossible.     

3个鸡群体中4个微卫星DNA多态性及其与杂种优势的关系

利用4个微卫星标记（ADL101、MCW020、ADL183、ADL298）对玫瑰冠鸡、新罗曼鸡和安卡红鸡的等位基因频率、群体多态信息含量、有效等位基因数、杂合度和遗传距离进行了遗传检测,并测定了玫瑰冠鸡与安卡红鸡及新罗曼鸡的杂交效果。结果表明,4个微卫星标记在玫瑰冠鸡、安卡红鸡和新罗曼鸡3个群体中存在多态性,可以用于鸡遗传多样性的评估;从不同的群体来看,安卡红肉鸡遗传变异程度最大,而玫瑰冠鸡的遗传变异程度相对较小;玫瑰冠鸡与安卡红鸡的遗传距离大于其与新罗曼鸡的遗传距离,玫瑰冠鸡与安卡红鸡的杂种优势高于与新罗曼鸡的杂种优势,与实际杂种优势测定结果相符。     

切花小菊分枝性状杂种优势表现与遗传分析

 切花小菊的分枝是最重要的品质性状之一。用不同分枝特性的切花小菊品种‘QX-145’（作 母本）和‘南农银山’（作父本）杂交获得F1 群体,对F1 杂种的一级分枝数、分枝高度、一级分枝长度 和分枝角度等4 个分枝性状在2011 和2012 两个年度的表型数据进行记载,运用单个分离世代的主基因 + 多基因混合遗传分析方法,对其进行遗传分析。结果表明,4 个分枝性状在F1 群体中广泛分离,变异系 数为14.60% ~ 38.89%;杂种优势和超亲分离现象普遍存在,除一级分枝长度外,其他3 个性状的中亲优 势值均达极显著水平,中亲优势率分别为–21.46%、–46.96%和–8.85%。混合遗传分析表明：切花小菊 一级分枝长度、分枝角度符合A-0 模型,无主基因控制;一级分枝数和分枝高度符合A-4 模型,主基因 表现为负向完全显性,主基因遗传率分别为51.45%和53.92%。     

早熟禾的人工杂交有杂种优势预测研究

对草地早熟和品种间及基与变种秆早熟禾之间进行从工去雄杂交，对各杂交组合的后代进行了杂种优势预测，结果表明品种间杂交中莫诺波利草地早熟禾和瓦巴斯草地早熟禾的杂种在产草量方面有较强的优势，品种与变种杂交中扁秆早熟禾与思托佩草地早熟禾的杂种优势较强。     

秦川牛及其杂种牛生长性能及杂种优势研究

通过对4月龄纯种秦川牛(QQ)67头,安秦杂种牛(红安格斯牛♂×秦川牛♀,AQ)36头、德秦杂种牛(德国黄牛♂×秦川牛♀,DQ)14头和利秦杂种牛(利木赞牛♂×秦川牛♀,LQ)47头,共计164头牛生长发育性状特点及杂种优势的研究,发现LQ、DQ、AQ与QQ相比,在体重、体长、体高、胸围、十字部高等重要指标上具有明显的杂种优势。初步鉴定3个杂交组合后代在生长性能方面优于秦川牛纯种,表现杂种优势,达到改良目的。其中LQ与其他两个杂交群体相比,在生长发育过程中表现出更好的发育趋势,即LQ>DQ>AQ>QQ,是较为理想的杂交组合,而AQ和DQ群体在后期发育和被毛颜色上有不可替代的优越性。     

超级杂交稻杂种优势基因组水平的转录因子分析

本研究利用超级杂交稻组合两优培九及亲本(93-11、培矮64S)和已完成基因组测序的籼稻93-11和粳稻日本晴所配的籼粳杂交稻及亲本为材料,采用包含36926个单一基因的的寡聚核苷酸基因芯片进行亲本和杂交组合基因表达差异分析.结果表明在两优培九杂交组合中发现3488个差异表达基因,在Nipponbare/93-11组合中只发现有2416个差异表达基因.差异表达基因表现为多基因修饰模式,主要有加性效应,高或低亲本的显性效应,超显性和低显性.两优培九杂交组合中表现为加性效应有2317个主要差异基因,而Nipponbare/93-11组合中只有1055个主要差异基因表现为加性效应.两个杂交组合的差异表达基因的保守功能包括多个生物化学代谢途径的有关基因.比较亲本同源性基因调控区域发现大量的序列变化,这些变化在差异表达基因中更为丰富.上述发现证明了杂种优势产生的存在较复杂的分子机理.     

Genetic effects and heterosis of flowering and fruit characteristics of tropical pumpkin

Tropical pumpkin is an important vegetable in many lowland tropics. Estimation of genetic effects for a fixed set of genotypes may yield information on the presence of different types of gene action for important traits. Six landraces and one diallel set of their progeny were evaluated for time from planting to female anthesis and fruit characteristics. Variety effects and heterosis mean squares were significant for the days to female anthesis, the weight of the first mature fruit, the mean fruit weight and soluble solids, indicating the presence of both additive and non‐additive gene actions. Only variety effects were significant for the days to the first mature fruit. These characters could be improved by recurrent selection. Selection for heterosis would be effective except for the days to the first fruit to mature.     

泡桐优良无性系“TF33”干材表型性状杂种优势研究

以“毛泡桐×白花泡桐”的优良无性系TF33和两个标准对照品种(白花泡桐C001与兰考泡桐C125)为试验材料,研究了泡桐优良无性系干材表型性状的杂种优势.结果表明:(1) TF33、C001、C125无性系间各性状存在广泛和显著的变异;(2)3个生长性状(接干高、接干材积和主干材积)与3个干形性状(通直度、接干形数和主干平均削度)为高度变异性状(CV≥30％),CV变幅为33.10％～53.19％;(3)接干因子是影响和决定性状杂种优势最终状况和总体表现的最重要因素;(4)通直度性状的遗传改良是毛泡桐×白花泡桐杂种无性系干形遗传改良的关键和瓶颈;(5)多数性状间存在极显著或显著的相关性,且不同的性状间相关性变化较大;(6) TF33较C001有显著的材积生长杂种优势,较C125没有显著杂种优势.