樟树一年生幼苗遗传变异研究

对引种在福建省连城县姑田镇的樟树幼苗进行调查,结果表明,引种的24个家系生长良好,仅部分家系生长低于对照家系。方差分析的结果表明群体间生长差异显著。除苗高遗传力（0.52）以外,地径与材积的遗传力均为0.38,说明苗高受较强的遗传控制,而地径和材积受较弱的遗传控制。遗传变异系数与变幅说明群体个体间生长差异显著。通过对引种的24个家系进行聚类分析,可分为3类,速生家系为7个,多为广东的家系。中等家系和生长较差的家系中多以福建和江苏省的家系为主。     

大豆杂种第二代种子蛋白质、脂肪及其组份的配合力与遗传力分析

以 NCD-Ⅱ设计固定模型研究了3个东北大豆品种、5个美国品种(系)的 F_2代种子蛋白质、脂肪及其组份的配合力和遗传力。1.3个东北品种在产量、单株粒重、蛋白质、脂肪、蛋氨酸、亚麻酸含量、蛋白质总量、脂肪总量等11个性状上 gca 差异显著;5个美国品种(系)在蛋白质、油酸、亚麻酸含量等5个性状上有显著的 gca变异。各性状的加     

玉米种子活力的遗传力及活力与有关性状相关性的研究

种子活力问题是一个对育种和生产都十分重要的问题.玉米种子活力大小主要是由遗传特性决定的(68%左右),也受外界条件的影响,但影响较小.双亲活力对杂种一代活力的影响较大,利用活力的杂种优势能为生产带来潜力.玉米种子活力高低与幼苗长势有直线相关关系,与品种内百粒重呈曲线相关关系,与品种间百粒重关系不密切.播种较晚时,品种内植株成熟期长短与活力有负相关关系,与品种间成熟期长短关系不密切.玉米种子活力与胚大小也无密切关系.     

向日葵主要农艺性状的遗传分析

本试验对２０个向日葵品种的主要农艺性状进行了遗传分析。结果表明：出苗──现蕾日数，现蕾──开花日数，开花──成熟日数，叶片数、子仁率等农艺性状都有较大的遗传力。可以在早代单株选择或直接选择。而单株粒重、小区产量等遗传力较低的农艺性状应根据性状间相关关系进行间接选择或多环境选择。某性状的遗传改良效果由该性状的遗传力和变异幅度共同决定。     

深州蜜桃若干性状的变异与遗传倾向

 以深州蜜桃与大久保自然杂交后代为材料, 研究了26 个育种性状, 明确了各性状的变异系数、变异幅度以及次数分布曲线和组合遗传传递力。     

奶牛赘生乳头数遗传力的估计及其与产奶量的相关分析

奶牛赘生乳头数呈阈性状特点,本文采用阈性状分析法估测赘生乳头数的遗传力为0.33 0.04,因此,进行表型选择可获得较理想的选择效果。通过其对产奶量的相关分析表明,赘生乳头对产奶量虽无明显影响,但有遗传倾向。它不仅影响乳房的外形,也不利于机械化生产,无疑是一不合意性状,应在奶牛选种工作中予以重视。     

Morphological analysis and effect of selection for conformation in the Noriker draught horse population

To evaluate the breeding program in the Austrian Noriker draught horse population, which is mostly based on conformation, 31 body measurements from 497 horses in seven breeding areas of Austria were recorded. In addition, the data of 2376 horses (the current breeding population) from the studbook, containing 10 scored conformation traits and 4 body measurements per individual, were analysed. We assumed breeding regions, coat colour strains and breeding classes assigned according to conformation evaluation to be the main factors in phenotypic diversity of this Austrian draught horse breed. Significant differences and distances were found for all of these factors. Whereas differences between breeding areas mostly are due to housing conditions and feeding strategies, the breeding classes provide a very distinct picture of the current trends in Noriker breeding. Breeding organisations favour a long and high Noriker draught horse, a tendency that is the same for all departments. Heritability estimates for morphological traits vary from 0 to 0.67, and from 0.08 to 0.37 for linear type traits.     

Genetic associations between accumulated productivity, and reproductive and growth traits in Nelore cattle

The total meat yield in a beef cattle production cycle is economically very important and depends on the number of calves born per year or birth season, being directly related to reproductive potential. Accumulated Productivity (ACP) is an index that expresses a cow's capacity to give birth regularly at a young age and to wean animals of greater body weight. Using data from cattle participating in the “Program for Genetic Improvement of the Nelore Breed” (PMGRN — Nelore Brasil), bi-trait analyses were performed using the Restricted Maximum Likelihood method based on an ACP animal model and the following traits: age at first calving (AFC), female body weight adjusted for 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted for 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. Median estimated ACP heritability was 0.19 and the genetic correlations with AFC, BW365, BW450, SC365, SC450, SC550 and SC730 were 0.33, 0.70, 0.65, 0.08, 0.07, 0.12 and 0.16, respectively. ACP increased and AFC decreased over time, revealing that the selection criteria genetically improved these traits. Selection based on ACP appears to favor the heaviest females at 365 and 450 days of age who showed better reproductive performance as regards AFC. Scrotal circumference was not genetically associated with ACP.     

Stand establishment and early field vigour variation in a tropicalised shrunken-2 maize population

Low field emergence and early field vigour are major problems in shrunken-2 maize (sh-2). The genetic variability for stand-ability and early field vigour in a shrunken-2 maize population previously improved for adaptability to a tropical environment was investigated using a Design I mating system in which 40 randomly sampled males were crossed to four randomly sampled plants that served as females. Plants of the 160 crosses, representing full- and half-sib relationships, were evaluated in four sets, each composed of 40 crosses derived from 10 males during two growing seasons. Experimental design was randomized complete block with three replications. Difference in Emergence Index (EI) was not significant between the two seasons. Emergence Percentage (E%), Emergence Rate Index (ERI), and early field vigour traits viz. vigour score and seedling height determined at 28 days after planting (DAP) were, however, significantly (P < 0.05–P < 0.01) better in the first growing season. For all traits, the ‘female/male’ item was significant (P < 0.01) while ‘male’ was mostly non-significant. ‘Season × female/male’ interaction was significant for stand establishment traits but not for early field vigour traits. Averaged over all traits, dominance variance was 8.2 times higher than additive variance. Genetic variation for stand establishment and early field vigour in the tropicalised shrunken-2 maize population would be best exploited through the development of inbred lines, hybrids and synthetics. Broad-sense heritability was 53.0% for E%, 36.0% for EI, 33.0% for ERI, 71.5% for vigour score and 90.0% for seedling height. One hundred-seed weight ranged between 82.0 and 182.0 mg but correlation coefficients between seed weight on one hand, and E%, EI, ERI, vigour score and plant height on the other hand, were low (mostly <0.30) and, in general, non-significant. Emergence percentage had the highest average genotypic correlation value with the other traits studied (Mean Absolute Value = 0.71 in the first season and 0.45 in the second season). Emergence percentage, determined 10 days after planting, thus has potential for use as a selection index for stand establishment and early field vigour.