不同选择条件下预期遗传进度的可靠性分析

从遗传力与回归系数的关系入手．通过对亲子回归中子代平均数理论估计值Ｙ的误差进行分析，结果表明：遗传力是一个群体概念，不适合估算个体的遗传进度．特别是在遗传力较低或选择差较小时，个体的遗传进度估计值的可靠性更差；用遗传力估算由多个个体组成的小群体的遗传进度时，其遗传进度估计值的可靠性将大大提高．只要入选样本容量足够大．其遗传进度估计值的误差估计可以降低到允许的范围．     

云南松天然林分遗传增益研究

调查了永仁县白马河林场云南松优良林分子代测定试验林树高和地径，估算优良林分的遗传力和遗传增益。结果表明：天然云南松优良林分子代林树高生长量的遗传力为87．9％，与对照相比遗传增益为5．7％；地径生长量的遗传力为52．6％，遗传增益为8．6％。     

林木无性系育种若干遗传参数估算的研究进展

遗传参数估算是林木育种程序中最主要的环节之一。林木无性系育种具有方法简单、投产迅速和增益较高，但其遗传参数的估算方法却不尽完善。目前，几乎所有的无性系育种研究都采用有性育种的估算方法来估算遗传参数，这难免不影响估算的精度或使结论产生偏差。本文深入分析了无性繁殖材料的特点，推出了估算无性系材料遗传参数估算的精确算式。同时，对当前广为关注的无性系混种数目问题进行了理论探讨和定量描述。     

云南松母树林早期遗传增益的研究

作者在永仁县白马河林场做了３个不同种源５０个林分云南松母树林子代林的遗传测定试验，对３年和一的子代林树高、地径进行了方差、遗传力、实际增益、遗传增益的分析计算，并对不同种源的子代林树高、地径、进行了对比分析与方差分析。结果表明：不同种源母树林子代林与商品种子代林之间在树高、地径生长上均存在较大的差异；树高生长具有较大的遗传力，遗传增益为８．４２％；不同地域的云南松母树林第一代子代初期的表现性状均较     

刺槐主要性状遗传参数估算

刺槐主要性状遗传参数估算①甘雨（河南省林科所）李柏兴（郑州市园林局）吉顺祥赵天顺（孟州市林科所）师平钧（嵩县林业局）树木表现的性状是其基因型和外界环境共同作用的结果。树木性状遗传参数估算是林木育种的基础，它直接影响着树木育种策略的制定，并对育种效果的...     

樟子松遗传改良研究概述

对樟子松遗传改良20多年的研究工作进行了全面总结，在樟子松种源选择与区划、樟子松形态类型、种子园及母树林营建技术、子代测定与家系选择及综合选育遗传增益等方面的研究，取得了可喜成果，为樟子松生产提供了有益的参考。     

黑杨派无性系选择研究

汇集黑杨无性系27个，以生长性状为主，兼顾形质、适应性、抗病虫能力、材性，选出5个优良无性系：L802、中菏一号、L-323、L-324和I-102／74，与对照I-214材积相比，具有较高遗传增益，分别为115．5％、128．7％、95．1％、95．8％、107．4％：与I-69相比材积遗传增益分别为33．0％、42．5％、21．0％、21．7％、28．4％；同时形质指标也得到了较好的改良，具有生长快、造林成活率高、树干通直、抗病虫能力强、材质优等特点。     

云南松母树林早期遗传增益的研究

作者在永仁县白马河林场做了３个不同种源５０个林分云南松母树林子代林的遗传测定试验，对３年生的子代林树高、地径进行了方差、遗传力、实际增益、遗传增益的分析计算，并对不同种源的子代林树高、地径、进行了对比分析与方差分析。结果表明：不同种源母树林子代林与商品种子代林之间在树高、地径生长上均存在较大的差异；树高生长具有较大的遗传力，遗传增益为８．４２％；不同地域的云南松母树林第一代子代初期的表现性状均较稳定，用母树林种子造林能够大幅度地提高云南松林木材生产量。     

蓝桉、直干桉优树子代的遗传参数和预期增益

对蓝桉、干直桉实生种子园内优树子代主要性状的家系遗传力、单株遗传力和遗传变异系数分年度进行了估算,并预测其遗传增益。分析了性状间表型、遗传和环境的相关关系。用遗传相关矩阵作主分量分析,按综合指标对家系进行了分类、找出了表现优异的家系。提出了改良这两个树种主要性状的方法和预期效果,为今后制定育种方案提供有关的依据。     

滇西云南松天然优良林分半同胞子代测定

以腾冲古永林场所设的９个云南松天然优良林分固定样地为参试单元，设大理、保山商品种作对照，进行滇西地区云南松天然优良林分半同胞子代测定试验。经７年试验，探讨了子测林生长、材质、结实诸性状的关系；估算了优良林分子代初期的实际遗传增益和主要遗传参数。结果显示：该区云南松天然优良林分子代７年生时树高、胸径、材积和木纹理扭转度的实际增益分别达到：３７．４９％、６５．６０％、２１９．８４％和２６９．５７％；遗传增益分别为：２０．１４％、４０．４６％、１０７．１１％和５９．７９％，已远远超过云南松天然优良林分子代遗传增益３％的攻关考核指标。通过试验反馈表明了所制定的滇西地区云南松天然优良林分选择方法及标准具有科学性和可靠性     

A comparison of collinearity mitigation techniques used in predicting BLUP breeding values and genetic gains over generations

Collinearity potentially has a negative impact on the prediction of genetic gains in tree breeding programs. This study investigated the reliability and impact of best linear unbiased prediction (BLUP) using various collinearity mitigation techniques and of two computational numerical precisions on the genetic gains in breeding populations. Multiple-trait, multiple-trial BLUP selection scenarios were run on Eucalyptus grandis (F₁ F₂ and F₃) and Pinus patula (F₁ and F₂) data, comparing predicted breeding values of parents (forward prediction) with those realised in progeny (backward prediction of parents). Numeric precision had an impact on intergenerational correlations of BLUPs of some scenarios, indicating that it may not always be optimal to use higher precision when there is collinearity in the data. The relative difference in genetic gains between techniques varied by up to 0.38 standard deviation units in the less-stable pine population. This highlights the potentially large impact that instability can have on the efficiency of a breeding programme. BLUP performed close to expected in the relatively stable (less collinear) population (eucalypt F.,), and performed poorly in the other two populations. In the unstable pine data, some of the techniques resulted in improved intergenerational correlations coming in line with expected performance. This study indicates that BLUP can perform as expected and also confirms the potential problem of instability and consequences thereof. BLUP users should examine the nature of the population of predicted values and should these be outside expectation, various mitigation techniques should be explored.     

马尾松天然群体的遗传变异

对于育种工作者来讲,只有了解和掌握林木群体的遗传变异模式和规律,才能充分发掘其遗传潜力,制定合理的育种策略,从而获得较大的遗传增益。马尾松(Pinus massonianaLamb.)乃是我国南方各省主要的工业用材树种,遗传变异极为丰富,具有很大的选择潜力。众多的性状(包括生长、形态、物候、开花结实性和适应性等)都存在着丰富的地理遗传变异     

Realised genetic gains and estimated genetic parameters of two Eucalyptus grandis × E. urophylla hybrid breeding strategies

Conventionally, Eucalyptus grandis × E. urophylla (GU) hybrid material is first tested as seedlings in progeny trials for at least four years before ortets are selected and ramets of the selected ortets are propagated to test in clonal trials. The primary constraint with this ‘conventional hybrid breeding strategy’ (CHBS) is the time required to first test the hybrid material as seedlings. In order to address this, an ‘accelerated hybrid breeding strategy’ (AHBS) was investigated to reduce the time spent on testing GU hybrid material as seedlings. However, it is of utmost importance to quantify the impact the AHBS might have on genetic gains and genetic information. With this in mind, two clonal populations have been established with genetic material that derived from the CHBS and the AHBS. The main purpose of this study was to do a comparative study between the CHBS and AHBS, firstly to quantify the genetic gains per unit time for GU hybrid clonal populations that have been derived from the CHBS and AHBS respectively, and secondly to obtain genetic parameters such as heritabilities, the ratio of dominance, clonal within family variance, and the proportion of additive and non-additive genetic variance. The results indicated that the percentage realised volume gains per year was higher for the AHBS (3.7%) than for the CHBS (1.9%) when compared with the GU commercial clone. Thus, shortening the testing time of GU seedlings had a positive impact on volume gains per year. With regard to genetic parameters, both the AHBS and CHBS clonal populations indicated that non-additive genetic variation explained the majority (88% and 71%, respectively) of the genetic variation. Due to the pre-eminence of non-additive genetic variation, the narrow-sense heritabilties for the female and male effects were negligible for both clonal populations. Overall, the majority of the non-additive genetic variation was explained by the proportion of dominance variance, and less by the clone within family effect. These results suggest that, firstly, the time spent on testing GU hybrid material as seedlings should be minimised and, secondly, a hybrid breeding strategy to capture non-additive genetic variation should be adopted.     

Estimates of genetic parameters and genetic gains for growth traits of two Eucalyptus urophylla populations in Zululand,South Africa

In South Africa, Eucalyptus urophylla is an important species due to its disease tolerance to fungal diseases such as Crysoporthe austroafricana and the Coniothyrium sp. cankers. It is mainly planted as a parental species in a hybrid combination with E. grandis. Generally, the E. grandis × E. urophylla hybrid has better disease tolerance and higher wood density than pure E. grandis. The current strategy is to maintain large breeding populations of both parental species in order to provide improved elite selections for hybrid crosses on a regular basis. With this in mind, two E. urophylla populations, consisting of five provenance/progeny trials, were established in the subtropical region of Zululand. The aims of this study were, firstly, to determine the magnitude of genotype × environment interaction of E. urophylla in Zululand; secondly, to estimate genetic parameters and correlations for diameter at breast height (DBH), height and volume; and thirdly, to identify selections to advance the current breeding population as well as to hybridise with E. grandis. Results indicated that genotype × environment interaction effects would be practically negligible for growth in Zululand and therefore a single breeding population will be appropriate. In general, all growth traits were under low to moderate genetic control, with narrow-sense heritabilities ranging between 0.14 and 0.48 for volume. The genetic correlations between growth traits were high (0.98 and 0.99 for DBH– volume). This is an indication that DBH is a sufficient growth measure to use in E. urophylla breeding programmes. Best linear unbiased prediction estimates indicated that aa selection scenario of 200 individuals will generate genetic gains of 44.7% over the population mean. The estimated gains for the top 50 individuals that could potentially be used as hybrid parents to cross with E. grandis was 59.8% over the population mean.     

林木种子园的生态学意义及提高增益的关键技术

林木种子园为现代林业生产提供大量优质种源,是规模化造林成败与否的关键因子之一.本文在综述现代林木种子园分类和建园技术路线的基础上,分析了种子园的生态学意义和对进化适应的贡献,总结出提高种子园遗传增益的关键技术.     

秃杉半同胞家系生长性状的遗传分析及初选

通过对从云南昌宁、云南龙陵引进的17个秃杉半同胞家系实生林的长期观测,进行了秃杉生长形状的遗传分析及初步选择。结果表明:各半同胞家系在第5、15、24年,生长性状差异达到显著水平以上,这些差异主要由其本身的遗传特性决定,受中、强遗传力的控制,而受环境控制较弱。所有半同胞家系中,24年生14号、2号、17号、16号的树高、胸径和材积的均值分别为13.64 m、18.29 cm和0.1877 m^3,遗传增益的平均值分别为5.2%、4.38%和15.85%;选择出6株优良个体,24年生树高、胸径和材积的平均值分别为17.6 m、29.12 cm和0.5886 m^3,遗传增益的平均值分别为14.13%、14.73%和69.83%,这些优良半同胞家系和优良个体表现出突出的生长优势,可作为种子园和采穗圃材料。     

速生乡土树种黎蒴优树半同胞家系子代测定

将采自广东的278个黎蒴优树家系种植在广东东江林场和梅南林场,进行半同胞子代测定。造林5年后,对参试家系的3个主要生长性状进行调查分析。黎蒴家系树高、胸径和材积存在显著差异,遗传变异系数在13．60％～67．13％,且变异主要受遗传控制,其家系遗传力分别为0．511～0．543,0．585～0．736和0．469～0．717;相关性分析发现,材积生长量主要受胸径影响,其相关系数大于0．80。在10％～30％入选条件下,各生长性状均具有较高的遗传增益,其中材积遗传增益〉胸径遗传增益〉树高遗传增益。采用育种值评估法与综合指数法共选出优良家系36个、优良单株71株。研究结果为进一步开展黎蒴选育和遗传分析奠定了坚买基础。     

台山红岭种子园湿地松基因资源引入效果分析

１９８９年至１９９６年间,台山红岭种子园从美国、澳大利亚、津巴布韦引入湿地松基因资源种子共４０７份,包括有６个种源、２１３个全同胞家系和１８８个半同胞家系。利用其中３７０份材料营建种源林１片、基因资源林６片,面积共１６．８５ｈｍ＾２。根据这７片测定林的调查数据分析了新引材料的遗传品质以及选择潜力,造林保存率平均达９０％以上;在生长量方面,有６６．６７％的种源、８２．１４％的家系优于台山湿地松初级种     

桉树杂交种生长及抗风性状的遗传分析和选择

为了筛选出优良家系及单株,为桉树良种改良提供优质的遗传材料,对27月生30个桉树杂种家系试验林的生长和抗风能力进行分析和遗传评估.结果表明:试验林的树高(H)、胸径(D)、材积(V)、抗风指数(WR)在家系水平上、家系×重复交互作用水平上均存在极显著的差异(P＜0.01),在家系水平上4个性状均受到较高程度的遗传控制,单株水平上H、D、V3个性状受到较高强度的遗传控制,而WR受到较弱程度的遗传控制.遗传相关分析表明H、D、V、WR4个性状两两之间都呈极显著正相关(P＜0.01),其中,在生长性状中,D与V之间的相关关系最为密切;在抗风能力方面,WR与D之间的相关关系最为密切.通过构建性状选择指数方程,按照选择标准选出8个优良家系,39个优良单株,入选率分别为26.67％、5.65％.其中优良家系的遗传增益在H、D、V和WR上分别达到了8.24％、9.99％、25.24％和3.76％,优良单株的遗传增益在H、D、V和WR上分别为22.55％、13.45％、105.49％和1.90％.     

A comparison of deterministically predicted genetic gains with those realised in a South African Eucalyptus grandis breeding program

Tree breeders attempt to predict the genetic gains that are likely to be achieved through selection and breeding of new generations, using stochastic or deterministic modelling. There are many factors that may cause a discrepancy between the predicted and realised genetic gains. Often the predictions for genetic gains are based on single trait selection, whereas in reality the breeding tends to be multitrait in nature. The violation of Hardy-Weinberg conditions, assumptions regarding outcrossing and relatedness, assumptions regarding the effect of the interaction between the environment and the genotype, and numerous possible errors in the process of breeding, all could result in unexpected discrepancies between the realised and predicted genetic gains. A series of genetic gains trials containing representatives of three generations of Eucalyptus grandis selections were compared with the view to verifying the effectiveness of the E. grandis breeding program. Genetic gains of the F₃ (third generation of pedigreed progeny) over the F₂ generation (second generation of pedigreed progeny) were 15% for tree growth (volume). A comparison between F₂ and P₀ revealed an improvement of between 20% and 33% for growth. This exercise highlighted complexities of modelling the predicted genetic gains of assimilated genetic breeding trials. The predictions of genetic gains did deviate (in both directions) from those realised, although these deviations may be explained as functions of imperfect modelling. On average, however, the predicted genetic gains for tree volume over three generations was 13% between generations, whereas the average realised genetic gain in the genetic gains trial was 14%. It is therefore assumed that the E. grandis breeding population is indeed performing as expected, following classical tree breeding assumptions.