Selection on multiple QTL with control of gene diversity and inbreeding for long-term benefit

The purpose of this study was to develop and investigate selection strategies that aim at maximizing long-term genetic response while conserving gene diversity and controlling inbreeding in populations of limited effective size, assuming complete knowledge of all genes affecting a quantitative trait. Three selection strategies were proposed to select on 100 quantitative trait loci (QTL) and compared with truncation selection on breeding value. Alternative selection strategies aimed at maximizing the average breeding value of parents with a penalty on (1) the number of unfavourable QTL genotypes among parents (OS-I), (2) the negative of the logarithm of the frequency of the favourable allele at each QTL among parents (OS-II), and (3) the average pedigree relationship among parents (OS-III). When all QTL and their effects were known, the strategies examined were able to obtain extra long-term responses, conserve QTL diversity and reduce inbreeding, compared with truncation selection. Strategy OS-II was the most effective in conserving QTL diversity and OS-III in reducing inbreeding. By changing the magnitude of the penalties applied, the impact on long-term response, inbreeding and diversity can be controlled. Extra long-term responses over truncation selection of OS-I and OS-II were even greater when effects of QTL were estimated rather than assumed known, indicating the applicability of results to practical strategies for marker-assisted selection. Extra responses are expected to be reduced for larger population sizes.     

新疆塔里木盆地两河流域野生麻资源调查

麻具有药用、轻纺、保健、造纸、制作药烟、蜜源等多种经济价值.新疆塔里木盆地两河(叶尔羌河、塔里木河)流域是野生麻(大叶白麻Poacynum hendersonii、白麻P.pictum、罗布麻Apocynum venetum)的主要产区,其中大叶白麻分布广,面积大,储量多.按有关分类方法,将野生麻资源划分为6个群系12个群丛.野生麻分布面积23.56万hm2,有麻面积18.12万hm2,其中大叶白麻占99.51%;白麻占0.49%.鲜麻总产量59.35万t,折合干麻总产量24.41万t.为更好的利用野生麻资源,在对其种类、分布、面积、生物量调查的基础上,对麻的开发前景、野生麻田的保护管理及改良培育、人工麻田的建立、科技攻关5个方面提出了建议.     

德国黑麦草在四川的生长适应性比较

连续2年种植29个德国引进黑麦草Lolium spp.品种,以Tetragold和野生黑麦草为对照,综合评比各黑麦草品种的分蘖力、株高、植株鲜质量、抽穗期和成熟期等生长性状,筛选性状优良、在四川具有较强适应性的黑麦草品种。结果表明：Taurus、Barfort、Gemini、Fastyl 4个黑麦草品种表现出优良的综合生长性状,在四川地区适应性强,可用于引进品种推广应用研究;Licarno、Bartissimo、Alamo拔节速度快,抽穗前植株较高,Tosca、Zarastro、Remy分蘖力强,Lolita植株鲜质量产量高,Defo、Prestyl、Pomerol花期迟,生育期、供草期长,可作为选育当家品种的远缘优良亲本材料。     

柔嫩艾美耳球虫早熟株的初步选育及免疫原性的测定

为选育柔嫩艾美耳球虫的早熟株和了解其免疫原性,本试验通过鸡体的传代培养,初步得到了柔嫩艾美耳球虫早熟株P9。以早熟株免疫雏鸡后,以亲本株P0半数致死量攻毒,以确定其免疫原性。结果表明:P9的潜隐期由P0的141h缩短至131.5h,免疫后攻毒显示该早熟株具有良好的免疫原性。     

轮回选择培育紫花苜蓿耐盐新品系

经过二代轮回选择和一代混合选择得到的70个耐盐优株相互杂交的后代群体为材料,在含盐量为0.3%~0.5%的盐碱地上种植,通过表型选择挑出106个耐盐优株,并进行了耐盐性一般配合力的测定,其中耐盐性一般配合力高的植株73株,中等的23株,较低的10株。淘汰一般配合力较低和中等的植株,让耐盐性一般配合力高的优株相互杂交,完成第三代轮回选择,得到了耐盐优株相互杂交的耐盐苜蓿新品系。     

不同扦插方式对“商薯19”产量影响研究

为挖掘“商薯19”的增产潜力,以商洛市农户常用的竖插法为对照,采用单株水平扦插法、双株水平扦插法栽培“商薯19”。结果发现双株水平扦插法总产量最高(3 037.81 kg/667 m²),与竖插法产量(1 838.7 kg/667 m²)差异显著(P<0.05)。进一步统计不同扦插方式的大、中薯数量、产量及大、中薯率发现,双株水平扦插法主要通过增加大薯产量和中薯数量来达到增产效果。双株水平扦插法能够同时适应生产淀粉和鲜食的需求,有必要进一步试验、示范和推广。     

猪主要经济性状的基因组选择研究

旨在系统比较GBLUP、SSGBLUP、BayesA、BayesB、BayesC、BayesLASSO、BSLMM和BayesR等8种方法对猪重要经济性状基因组选择的准确性。本研究以本实验室收集的2 585头大白猪达100kg日龄、达100kg背膘厚和母猪乳头数3个性状为分析对象,结合猪50K基因芯片分型数据,以加性模型为基础,利用5倍交叉验证比较8种方法的基因组选择准确性。研究发现,基因组选择的准确性与不同性状估计遗传力呈正相关。交叉验证结果表明,预测准确性最高的性状为达100kg日龄,但不同方法在不同性状中表现并不完全相同,在达100kg日龄和达100kg背膘厚中SSGBLUP基因组预测准确性均为最高,而在母猪乳头数中BayesA的基因组预测准确性最高。综上表明,对小样本开展基因组预测时,中、高等遗传力性状可以选择SSGBLUP方法,低等遗传力性状可以选择BayesA方法。如何优化和选择一种广泛适用于所有性状的方法,可能是未来研究的方向。     

Sperm competition and the evolution of sperm form and function in mammals

Sperm competition is a powerful selective force that has influenced many reproductive traits in males and females although additional evolutionary explanations may help to understand the diversity of mammalian reproduction. Sperm morphology varies considerably in mammals with extreme examples in several rodent lineages in which a wide range of sizes and complex head morphologies have been identified. Mammalian spermatozoa also differ in function, with swimming velocity and trajectory showing much divergence. Underlying processes mediating function have received little attention so far, but differences in timing and proportion of sperm undergoing capacitation or acrosomal exocytosis may be related to variation in signalling processes. Furthermore, energy required for sperm functions (such as motion, signalling and overall maintenance of cell integrity) can be produced and consumed, following different patterns among species and this could be the result of several selective forces. A more thorough understanding of the diversity in structure and function of sperm cells, and underlying selective forces, may help us develop better methods to assess them taking into account particulars and generalities of sperm form and performance. Such tests could then become more reliable in estimations of the impact of cryopreservation or effect of changes in the environment and their relevance for fertility.