Heritability of frost-seeded red clover establishment

In the colder parts of the United States (north of 32° N latitude and east of 92° W longitude), in late winter after disappearance of snow cover, red clover (Trifolium pratense) is often broadcast seeded into forage legume-depleted grass pastures to increase pasture forage quality. This method of establishment is referred to as frost seeding. However, in an estimated 30–40% of frost seeded pastures in Wisconsin, USA the legumes fail to establish. In this study 40 red clover halfsib families from one breeding population and ten check populations were evaluated for spring frost-seeded establishment in three environments. Seedling establishment counts and plant heights were measured 3 months after frost-seeded planting. One of the three environments experienced a stand establishment failure. Narrow sense heritability estimates on a halfsib family basis for stand counts and heights were 0.07 and 0.63, respectively. Seedling counts were greatly affected by environment with micro-environmental effects contributing to low heritability. Additive by environment genetic variance was large, again leading to low seedling count heritabilities. These results, based on one population, suggest that it may be difficult to select for increased frost-seeded seedling establishment and that many test environments are needed to achieve genetic gains for this trait. In comparison, seedling height was very heritable with relatively small additive by environment genetic variances. The genetic correlation between seedling count and height using frost-seeded establishment was r _A = 0.42.     

几个水稻新恢复系的应用前景分析

用8个新恢复系与川香29A(A1)、珍汕97A(A2)、Ⅱ-32A(A3)３个不育系按不完全双列杂交配组24个杂交组合，通过24个组合12个性状的主要性状观测值、配合力及遗传力对几个新恢复系的应用前景进行分析，进而作亲本与组合的优势评价，结果：新恢复系以R9最为理想亲本，R8、R7为较理想亲本；从特殊配合力效应值来看，组合中A2R2、A1R5、A3R9这3个组合较为理想。从性状观测值来看，A2R9、A3R9、A1R3、A1R9、A1R8这5个组合较为理想     

Genetic variation,heritability and correlations of agro-morphological traits in tall fescue (<Emphasis Type="Italic">Festuca arundinacea</Emphasis> Schreb.)

To study the genetic variation, heritability and genetic correlations of some agro-morphological traits in tall fescue, 25 parents from a genetically broad-base germplasm were polycrossed and their respective half-sib families were generated. Clonally propagated parents and their half-sib families were grown as spaced single plants using a randomized complete-block design with three replications, and observed for seven traits in 2006 and 2007. The estimates of broad-sense heritability were moderate to high for the traits studied. Narrow-sense heritability estimates from analyses of progenies and from regression of half-sib (HS) progenies on parents suggested that genetic variation for these traits was largely controlled by additive gene action. Association of dry matter yield (DMY) with plant height, number of fertile shoot, curbs width and spring growth was positive and significant. With the exception of number of days to pollination, correlation coefficients of the traits between the parents and offspring were not significant. Based on parent-offspring regression, genetic gain from selection for DMY was high, demonstrating genetic potential for improving this trait. Overall, there was high genetic variation and moderate heritability for most traits in the tall fescue populations evaluated. In conclusion, to improve herbage yield, selection would be more effective based on forage yield components.     

Juvenile genetic parameter estimates for vigour,stem form,branching habit and survival in three radiata pine (<Emphasis Type="Italic">Pinus radiata</Emphasis> D.Don) progeny tests in Galicia,NW Spain

Individual and family heritabilities, as well as phenotypic and genetic correlations were estimated 2 and 3 years after plantation, in progeny tests carried out in plantations of open-pollinated Pinus radiata D.Don progeny located at three different sites in Galicia (NW Spain). The following factors were considered: survival, growth (free growth, height, diameter, volume, height/diameter ratio), form (number of branches, number of whorls, number of branches per whorl, number of branches per tree height meter, number of ramicorn branches, diameter of the thickest branch, internode length, branch angle, stem straightness, stem sinuosity, number of forks) and resistance (frost and insect resistance). Each plantation contained 50 female parents that had been selected as plus trees in genetically unimproved plantations in Galicia, as well as 6 female parents selected from the radiata pine breeding programme in the Basque Country (northern Spain) and two commercial lots of seed from Galicia, as controls. Individual heritabilities varied from low to high levels for each trait studied. Family heritabilities followed similar trends for individual heritabilities, but were of much greater magnitude. The results suggested that all traits except the number of branches per whorl and insect resistance could be expected to respond to selection based on individual performance. The less heritable traits could be improved by progeny testing. Height and diameter were strongly and positively correlated, and both traits were also correlated with the number of branches, the number of whorls and the branch diameter. The results are compared with previously published data and discussed in relation to the implications for breeding activities.     

南酸枣优树子代苗期性状变异初步研究

贵州省内选择出的19株优树子代进行了苗期测定,结果表明:各家系间在苗高、地径上均存在极显著差异,遗传变异系数分别为8.1%和18.6%,这些变异受强遗传控制,苗高与地径呈极显著相关,相关系数达0.639,地径指标对南酸枣进行优良家系选择中有着重要地位,通过苗期试验结果分析,选出优良家系4个。     

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。     

甘蓝抽薹期配合力及遗传力分析

以2个耐抽薹的甘蓝高代自交系和2个易抽薹的甘蓝高代自交系为亲本,按照Griffing完全双列杂交方法Ⅰ配制杂交组合,对其抽薹期性状进行配合力和遗传力分析。结果表明：耐抽薹自交系LN-0901和LN-0913的一般配合力和特殊配合力都较高,宜用于杂种优势育种。抽薹期性状主要由基因的加性效应控制,广义遗传力为96.42 %,狭义遗传力为67.68 %,在育种实践中适宜进行早期世代选择。     

大约克夏猪和长白猪肢蹄结实度的遗传分析

 对引入我国的大约克夏、长白猪的肢蹄结实度分别进行了遗传分析。肢蹄结实度按前、后肢分解为关节、蹄裂、蹄枕（蹄底增生）、偏蹄、X肢势、O肢势、蹄壳质地、总评分8个性状，进行量化评分。用我们推导的单元内混合家系相关法进行估算，大约克夏、长白猪的前、后肢总评分遗传力为0.15-0.30，单个肢蹄性状的遗传力为低到中等或稍高(0.02-0.34)；还估算了肢蹄性状与体尺性状、繁殖性状间表型相关及遗传相关。表明体型过大对肢蹄结实度不利，肢蹄结实度对母猪单窝繁殖力影响较小。根据遗传分析结果制定了肢蹄性状选择指数，提出了改进肢蹄结实度的措施。     

冬小麦生育期亚性状遗传研究

本文利用多年来的资料对小麦生育期亚性状(拔节期、抽穗期、开花期和成熟期)进行了遗传分析。结果证明:利用方差分析法估算的四个亚性状的遗传力都达到显著水平;F_2代,不同的组合、不同的亚性状遗传力各异;F_3代,早×晚的组合遗传力达到显著水平,而其它组合不显著;连续两年回交后代,只有早×晚的组合回交效果显著,而早×早,早×中的组合效果不显著。据此,在育种上,要根据不同的组合、不同的亚性状,采用不同的方法进行早代选择。